Gigatron TTL Microcomputer

In this hands-on lab, students construct a functional 8-bit general-purpose microcomputer from discrete 7400-series TTL and HCT integrated circuits without relying on a commercial microprocessor. Learners assemble through-hole passive components, logic gates, multiplexers, counters, registers, and memory onto a printed circuit board, systematically testing power rails, clock generation, and bus behavior at intermediate stages using a multimeter or oscilloscope. Through this build, students explore foundational computer architecture and digital logic at the lowest level, including the arithmetic logic unit (ALU), program counter, instruction decoding, register-transfer timing, passive digital-to-analog converter (DAC) video and audio generation, and software-driven input/output handling. Upon completion, students operate and evaluate the microcomputer running interactive games, fractal generators, a 6502 emulator, and a built-in Tiny BASIC interpreter.

computer architecture digital logic design TTL transistor-transistor logic 7400 series CPU design central processing unit microcomputer microprocessor systems digital electronics soldering through-hole assembly hardware debugging multimeter arithmetic logic unit ALU R-2R ladder DAC VGA generation retrocomputing Tiny BASIC

Uploaded by demo on 2026-07-09 · ready · Electronics · Original source ↗

Files: directions.md · assembly_manual.pdf · bom.xlsx

Readiness checks

  • complete 2026-09-03 00:05 🛡 Cybersecurity: Could not check 55 searches · 2 pages
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  • complete 2026-07-19 15:14 🛡 Cybersecurity: not checked 51 searches · 0 pages
    view · PDF
  • complete 2026-07-09 12:55 🛡 Cybersecurity: not checked 53 searches · 0 pages
    view · PDF

Latest report — 2026-09-03 00:05

Readiness: Gigatron TTL Microcomputer

Verdict: Ready with caveats · 2026-09-02 · est. parts cost $120–$150 (excludes PCB fabrication and enclosure) Cybersecurity — software & network: Could not check

All 39 logic ICs are Active and in stock, and two of the four problems flagged in the July report have fixed themselves: the 74HCT04 hex inverter and the DB9 gamepad plug are both back in DigiKey stock, so neither needs the substitute the last report recommended. Three items still need a deliberate choice when you order. The 32K SRAM named in the BOM is gone from authorized distribution entirely and must be substituted; DigiKey now holds only 27 of the 100 nF bypass capacitors and the board needs 40; and the 6.25 MHz crystal is stocked by exactly one distributor. Each of those has a verified answer below, so nothing blocks a build — but you cannot fill this BOM from a single DigiKey cart. The verdict is unchanged from 2026-07-19: the number of troubled parts is about the same, but which parts they are has changed.

Action required

Part Problem Recommended action
62256 SRAM (LY62256PL-55LLI) Unobtainable. DigiKey returns no match, and the ECIA authorized-distributor query returns "no ECIA-authorized distributor lists this exact part number". Substitute Alliance AS6C62256-55PCN, $10.13, 5,816 in stock. See Substitutes.
100 nF bypass cap (K104K10X7RF5UH5) ×40 New since the last report. DigiKey stock has fallen from 233,541 to 27 — not enough for one board. Either order the exact part from Newark (48,705 @ $0.276), or use the verified substitute K104K15X7RF5TH5 (345,661 @ $0.29).
6.25 MHz crystal (MP062-E) Zero stock at DigiKey with a 19-week factory lead time; only one distributor holds any. Buy from Mouser (1,000 @ $1.01). Do not substitute — the frequency sets the VGA timing.
74HCT32 (CD74HCT32EE4) The exact ordering code has zero DigiKey stock and a 16-week factory lead. Use CD74HCT32E ($1.02, 1,705) — identical package and electricals — or buy the EE4 code from Mouser (944 @ $1.01).
Wooden enclosure Discontinued since 2020; the BOM itself records "custom made, no longer available". Unchanged from the last report. Fabricate your own, or run the board bare. A community case design exists at thingiverse.com/thing:5445044.
Famicom-style gamepad Retail listings are dominated by Atari/Amiga DB9 joystick adapters, which the manual says will not work. Order only a Famicom/NES serial shift-register controller, e.g. the 9-pin FC controller at $2.05. Confirm the type with the seller before ordering — no listing was verified this run.

Cybersecurity — software & network

Could not check — Both software components are unversioned firmware with no package ecosystem and no advisory database, and the repository they come from publishes no manifest, release or commit to pin them to, so no vulnerability or support check was possible.

Component Version How known Support status
Gigatron System ROM (gigatron-rom) not determined not determined (The materials state that ROM v3 or newer is needed for PS/2 program saving and that v4/v5 add games and WozMon, but never state which ROM the kit's EPROM was burned with, and they pin no release or commit. Listing the repository this run showed its default branch (master) carrying ROMv1, ROMv2, ROMv3, ROMv4, ROMv5a and ROMv6 image files side by side, with no manifest of any kind at the root - only a Makefile.) —
BabelFish ATtiny85 keyboard-bridge firmware not determined unpinned (Tracked inside the gigatron-rom repository at Utils/BabelFish rather than released separately. Listing that directory this run showed an Arduino sketch (BabelFish.ino, PS2.ino) alongside prebuilt images BabelFish.ATtiny85.hex/.bin and an older BabelFish.ATtiny85_v1.hex/.bin, with no version file, manifest or lockfile.) —

No findings — but nothing was checkable this run. Read that as "not examined", not "clean"; the Not checked list below says why.

What this means for your lab

Nothing was actually scanned for vulnerabilities in this lab, because there is nothing scannable: both pieces of software are firmware burned into chips, and no vulnerability database covers that kind of code. Read the absence of findings below as 'not examined', not as 'clean'. The good news is that the exposure is genuinely small: the Gigatron has no network interface at all - no Ethernet, no Wi-Fi, and its Mini-USB connector is wired for 5 V power only, with the data pins unconnected - so there is nothing for someone else on your campus network to reach, and no network precautions are needed before students use it. The practical risk here is version drift rather than security. The lab's materials never say which ROM version the kit shipped with, and they point at the project's repository without naming a release or commit; when we listed that repository on 2 September 2026 its main branch carried ROM images up to ROMv6, which is newer than the v4/v5 the manual describes. So an instructor who re-burns an EPROM 'from the current repository' today can easily end up with a ROM that behaves differently from the one the manual documents. Decide which ROM version your course expects, write it down alongside the lab materials, and burn that specific image; the same applies to the ATtiny85 keyboard adapter, whose firmware is likewise unversioned.

Not checked

  • Gigatron System ROM (gigatron-rom): Vendor firmware burned into a 27C1024 EPROM: no package ecosystem and no vulnerability database covers it, so no advisory check is possible. The repository root was listed this run and holds no parseable manifest (a Makefile only), and no release or commit is pinned by the lab's materials, so there is also no version to check.
  • BabelFish ATtiny85 firmware: Bare-metal AVR firmware distributed as an Arduino sketch plus prebuilt .hex/.bin images inside the gigatron-rom repository. No advisory database covers Arduino/AVR firmware, and the directory listing this run showed no manifest, lockfile or version file, so neither a version check nor a vulnerability check is possible.

Parts

Discrete passives and protection

Part Spec/Package Status Stock Price Source Drift
K470J15C0GF5TL2 ×3 47 pF C0G disc, 5.0 mm lead spacing Active 23,798 $0.27 DigiKey +$0.01; stock −1,138
EEU-FC1E221 ×1 220 µF 25 V radial electrolytic Active 4,569 $0.60 DigiKey flat; stock −2,926
K104K10X7RF5UH5 ×40 100 nF 50 V X7R, 5.00 mm lead spacing Active, short stock 27 (DigiKey); 48,705 (Newark) $0.28 DigiKey / Newark DigiKey stock 233,541 → 27; price flat
MF-R075 ×1 PTC resettable fuse, 0.75 A hold, radial Active 3,617 $0.47 DigiKey flat; stock −987
MP062-E ×1 6.25 MHz crystal, HC-49/U, CL 30 pF, ESR 40 Ω Active, no DigiKey stock (19-week lead) 0 (DigiKey); 1,000 (Mouser) $1.01 Mouser flat price; Mouser 1,007 → 1,000; DigiKey now quotes a 19-week lead

Resistors and resistor networks

Part Spec/Package Status Stock Price Source Drift
CF14JT1M00 ×1 1 MΩ, 0.25 W axial Active 507,150 $0.10 DigiKey flat
CF14JT1K00 ×1 1 kΩ, 0.25 W axial Active 527,518 $0.10 DigiKey flat
CF14JT2K20 ×5 2.2 kΩ, 0.25 W axial Active 76,070 $0.10 DigiKey flat
CF14JT68R0 ×2 68 Ω, 0.25 W axial (VGA sync) Active 12,729 $0.10 DigiKey flat
CF14JT750R ×3 750 Ω, 0.25 W axial (RGB DAC high bits) Active 20,221 $0.10 DigiKey flat
CF14JT1K50 ×3 1.5 kΩ, 0.25 W axial (RGB DAC low bits) Active 44,718 $0.10 DigiKey flat
4605X-101-222LF ×3 2.2 kΩ bussed array, 5-SIP, 2.54 mm Active, thin at DigiKey 25 (DigiKey); 9,876 (Newark) $0.28 DigiKey / Newark DigiKey 32 → 25; price flat
4606X-R2R-103LF ×1 4-bit R-2R ladder, 10 kΩ, 6-SIP Active 1,367 $0.46 DigiKey flat

Diodes and optoelectronics

Part Spec/Package Status Stock Price Source Drift
1N5339B-TP ×1 5.6 V 5 W Zener, DO-15 Active 66,233 $1.34 DigiKey +$0.08
BAT42-TR ×30 Schottky signal diode, DO-35 Active 22,428 $0.50 DigiKey flat; ≈$15 for the 30 needed
HLMP1700C6A0 ×5 Red 3 mm LED, low-current Active 7,051 $0.28 DigiKey previous report priced a different manufacturer's part at $0.51

Active integrated circuits and supervisory

Part Spec/Package Status Stock Price Source Drift
SN74HCT04N ×1 Hex inverter, 14-DIP 0.300", 4.5–5.5 V Active 4,503 $0.96 DigiKey back in DigiKey stock (was out of stock; substitute no longer needed)
MCP100-450DI/TO ×1 Reset supervisor, TO-92 Active 8,646 $0.42 DigiKey flat
CD74HCT161E ×6 4-bit counter, 16-DIP Active 9,038 $1.34 DigiKey flat; stock −623
AT27C1024-70PU ×1 64K×16 EPROM, 40-DIP 0.600", 4.5–5.5 V Active, thin at DigiKey 87 (DigiKey); 566 (Mouser) $4.52 DigiKey 96 → 87; price flat
SN74HCT273N ×3 Octal D register, 20-DIP 0.300" Active 29,342 $0.93 DigiKey flat; stock +2,715
SN74HCT244N ×2 Octal 3-state buffer, 20-DIP 0.300" Active 3,350 $1.52 DigiKey flat; stock −1,117
SN74HCT139N ×1 Dual 2-to-4 decoder, 16-DIP Active 26,317 $1.26 DigiKey +$0.07
CD74HCT153E ×9 Dual 4-to-1 mux, 16-DIP Active 796 $1.22 DigiKey flat; stock −20
SN74HCT138N ×2 3-to-8 decoder, 16-DIP Active 3,107 $0.89 DigiKey flat; stock −314
SN74HCT240N ×1 Octal inverting buffer, 20-DIP Active 21,873 $0.96 DigiKey flat; stock −2,202
CD74HCT32EE4 ×1 Quad 2-input OR, 14-DIP 0.300" Active but no DigiKey stock (16-week lead) 0 (DigiKey); 944 (Mouser) $1.01 Mouser exact ordering code now at zero DigiKey stock; see Substitutes
CD74HCT283E ×2 4-bit full adder, 16-DIP Active 650 $1.40 DigiKey +$0.08; stock 915 → 650
SN74HCT377N ×3 Octal D flip-flop with enable, 20-DIP Active 10,063 $1.52 DigiKey +$0.09
SN74HCT157N ×4 Quad 2-to-1 mux, 16-DIP Active 33,628 $1.16 DigiKey flat
LY62256PL-55LLI ×1 32K×8 SRAM, 28-DIP 0.600", ≤ 70 ns Unobtainable — no DigiKey match, no ECIA-authorized distributor 0 — — unchanged (obsolete in July too); substitute now priced
SN74HC595N ×1 8-bit shift register, 16-DIP Active 4,836 $1.97 DigiKey +$0.11; stock 14,290 → 4,836

Connectors and sockets

Part Spec/Package Status Stock Price Source Drift
Molex 54819-0519 ×1 Mini-USB Type-B receptacle, R/A (DigiKey code 0548190519) Active 16,718 $2.07 DigiKey flat; stock 901 → 16,718
SJ1-3523N ×1 3.5 mm stereo jack, R/A through-hole Active 233,492 $1.12 DigiKey +$0.06
L77HDE15SD1CH4R ×1 HD-15 VGA female, R/A, 8.89 mm backset Active 980 $2.20 DigiKey +$0.13; stock 114 → 980
TE 5747840-3 ×1 DB9 male, R/A, 8.08 mm backset Active 3,374 $3.63 DigiKey back in DigiKey stock; price $2.87 → $3.63
On-Shore ED40DT ×1 40-pin DIP socket, 0.600" row pitch Active 9,683 $2.95 DigiKey — (previous report used an eBay assortment)
Assmann AR-28-HZL-TT ×1 28-pin DIP socket, 0.600" row, 2.54 mm pitch Active 2,925 $2.08 DigiKey — (previous report used an eBay assortment)

Mechanical, hardware and accessories

Part Spec/Package Status Stock Price Source Drift
Gigatron main PCB ×1 2-layer FR4, ~240 × 170 mm, HASL Design files published — not priced gigatronttl.eu / hackaday.io unchanged
Qualtek 3021055-03 ×1 USB-A to Mini-USB-B cable, ~1 m Active 2,935 $2.46 DigiKey — (no baseline)
TE Connectivity 12100 ×1 EPROM UV window foil label not checked — — — — (absent from the previous report)
Famicom-style clone gamepad ×1 8-button NES/Famicom serial, DB9 Available at retail; type must be confirmed — $2.05 Google Shopping previous report listed $4.95 (AliExpress, not re-checked)
Wooden enclosure + acrylic lid ×1 Custom laser-cut hardwood frame Discontinued (production ceased 2020) — — — unchanged
3M SJ-5302 CLEAR ×8 Bumpon feet, 7.9 mm × 5.6 mm Available; not stocked at DigiKey under this MPN 2,304 (Master Electronics); 236,304 (Mouser) $0.0888 Master Electronics previous report's DigiKey mini-pack ($14.70) no longer resolves; now ≈$0.09 per foot
Assembly manual ×1 59-page A4, wire-O bound Commodity print service — $0.96 Google Shopping — (no baseline; PDF is CC BY-SA 4.0)

Pluggy McPlugface (PS/2 keyboard daughterboard)

Part Spec/Package Status Stock Price Source Drift
Pluggy McPlugface PCB ×1 2-layer FR4, ~40 × 30 mm Design files published — not priced gigatronttl.eu / Tindie unchanged
Kycon KMDGX-6S-AS ×1 6-pin mini-DIN PS/2 female, R/A shielded Active 4,182 $1.88 DigiKey flat
Amphenol L77SDE09SOL2 ×1 DB9 female, R/A through-hole Active 1,382 $1.31 DigiKey +$0.07; stock −83
ATtiny85-20PU ×1 8-bit AVR MCU, 8-DIP 0.300" Active 21,937 $1.66 DigiKey flat; stock −3,022
Mill-Max 110-47-308-41-001000 ×1 8-pin DIP socket, 0.300" row pitch Active 1,180 $0.85 DigiKey — (no baseline)

Substitutes

For part Substitute Differences Verified Judgment
LY62256PL-55LLI (32K×8 SRAM) Alliance AS6C62256-55PCN — $10.13, 5,816 in stock Same 28-DIP 0.600" package and same 32K×8 organisation. Supply 2.7–5.5 V vs the lab's 5.0 V rail — wider than required, acceptable. Temperature 0 °C to 70 °C commercial, narrower than the original's industrial grade but ample for a classroom. At $10.13 it becomes the most expensive part in the BOM. verified: package + row pitch (28-DIP 0.600", DigiKey parametrics), supply range 2.7–5.5 V vs 5.0 V (DigiKey parametrics), 32K×8 organisation (DigiKey description). not verified: access-time grade — no parametric; the "-55" suffix is assumed to mean 55 ns Acceptable, and the only authorized-channel option — the specified part is listed by no ECIA distributor. Confirm 55 ns on the datasheet.
K104K10X7RF5UH5 (100 nF bypass) Vishay K104K15X7RF5TH5 — $0.29, 345,661 in stock Identical 0.1 µF, ±10%, 50 V, X7R, −55 °C to 125 °C. Same 0.197" (5.00 mm) lead spacing, same radial through-hole formed-lead style. Body 4.00 × 2.60 mm and 6.60 mm tall vs the original's 3.60 × 2.30 mm and 6.20 mm — 0.4 mm larger each way, worth a glance on a dense board but the hole pattern is unchanged. verified: capacitance, tolerance, voltage rating, dielectric, operating temperature, lead spacing (0.197"/5.00 mm on both) and mounting type — all from DigiKey parametrics on both parts Acceptable. DigiKey's own "Direct" substitute, and the practical way to buy 40 pieces in one order.
AT27C1024-70PU (EPROM) Microchip AT27C1024-45PU — $4.60, 197 in stock Same 40-DIP 0.600" package, same 4.5–5.5 V supply. The "-45" grade is faster than the "-70" the BOM asks for; exceeding the access-time requirement is fine. 8 cents dearer. verified: package + row pitch (40-DIP 0.600", DigiKey parametrics on both), supply range 4.5–5.5 V (DigiKey parametrics on both). not verified: access-time grade — suffix reading, no parametric Acceptable as a fallback. Keep the specified −70PU as first choice while it is stocked at six distributors. Either must be programmed before installation.
CD74HCT32EE4 (quad OR gate) TI CD74HCT32E — $1.02, 1,705 in stock DigiKey publishes identical parameters for the two ordering codes: 14-DIP (0.300", 7.62 mm), 14-PDIP supplier package, 4.5–5.5 V supply, 4 mA/4 mA output drive, −55 °C to 125 °C. Price differs by 53 cents at single quantity. verified: package + row pitch (14-DIP 0.300", DigiKey parametrics on both), supply range 4.5–5.5 V, output drive and operating temperature (DigiKey parametrics on both). not verified: what the "E4" suffix encodes — the evidence does not say Acceptable. Alternatively buy the exact EE4 code from Mouser at the same $1.01.

No substitute is offered for the 6.25 MHz crystal: its frequency sets the VGA scan timing, DigiKey's only suggestion (MP062) has no stock either, and the exact part is available from Mouser — buying it there is the answer.

Verify any substitute against its datasheet before ordering.

Other dependencies

  • Main board PCB fabrication — design files confirmed published. gigatronttl.eu states the PCB design files for both the Gigatron and Pluggy McPlugface were released; its About page (gigatronttl.eu/posts/17.html) lists "Gigatron PCB design (Gerbers)" and "Pluggy PCB design (Gerbers)"; hackaday.io project 20781 offers a 4.60 MB KiCad-and-Gerber zip archive. Fabrication cost not quoted this run.
  • Pluggy McPlugface PCB fabrication — same source. Ready-made bare boards for both are also sold on Tindie, and legacypixels.com lists a "Pluggy McPlugface Reloaded" PCB with components.
  • Enclosure fabrication — the original wooden enclosure is discontinued. A community case design is available at thingiverse.com/thing:5445044. The generic laser-cut-box results the search returned are not Gigatron-specific and are not a substitute.
  • Manual printing — commodity spiral-bound print services quote from $0.76 for the low-end options; the manual is CC BY-SA 4.0, so printing is optional.
  • Project websites — gigatronttl.eu and its About page appeared as live search results this run. gigatron.io, forum.gigatronttl.eu, the /walkthrough page and the /diagnostics page were not checked — no pages were fetched this run.

Watch list

  • 100 nF bypass capacitors (K104K10X7RF5UH5) — the sharpest move in this report: DigiKey stock fell from 233,541 to 27 while the board needs 40. Newark still holds 48,705 and the verified substitute holds 345,661, so this is a purchasing-route problem rather than a shortage — but watch whether the drop spreads to other distributors.
  • 6.25 MHz crystal (MP062-E) — one distributor with stock, and DigiKey now quotes a 19-week factory lead. If Mouser's 1,000 pieces go, this part becomes the build's hard stop, because the frequency cannot be substituted.
  • AT27C1024-70PU EPROM — 87 units at DigiKey, slowly declining (96 in July). Six distributors still hold stock and the −45PU grade is a verified fallback, but this remains the least replaceable IC in the design.
  • CD74HCT32EE4 — the exact ordering code went to zero DigiKey stock with a 16-week lead this cycle. Low consequence today because CD74HCT32E is interchangeable, but it shows this family's ordering codes churning.
  • 2.2 kΩ SIP arrays (4605X-101-222LF) — 25 at DigiKey, down from 32, and three are needed per board. Newark's 9,876 is the buffer.
  • 32K SRAM substitute (AS6C62256-55PCN) — now $10.13 and the most expensive part in the BOM. Worth re-pricing every cycle, since the original is gone and there is no cheaper verified drop-in.
  • Famicom gamepad — a retail commodity with no manufacturer part number, sourced from marketplaces whose listings turn over constantly, and easy to order wrongly (Atari-style DB9 joysticks do not work).
Snapshot What the lab depended on when it was uploaded — the baseline the readiness checks research against.

The Gigatron TTL Microcomputer is an educational 8-bit microcomputer whose central processing unit (CPU) is built purely out of discrete 7400-series TTL/HCT integrated circuit logic gates, multiplexers, counters, and arithmetic units without any microprocessor. The system operates on a single 5.0 V DC (±0.25 V) power rail drawing approximately 100 mA to 200 mA supplied via a Mini-USB connector. The CPU executes instructions fetched from a 1 Mbit (64K × 16) parallel EPROM clocked at 6.25 MHz by a crystal-driven hex inverter, reading and writing to a 32K × 8 static RAM (SRAM). Software running on the CPU generates 64-color 60 Hz VGA video directly using passive resistor-ladder digital-to-analog converters (DACs) and 4-channel audio via an R2R ladder DAC. User input is provided by a 9-pin Atari/Famicom gamepad, or through an optional "Pluggy McPlugface" companion adapter board containing an ATtiny85 microcontroller that translates PS/2 keyboard signals into gamepad inputs. All active components run at 5.0 V logic levels.

Bill of Materials

Discrete Passives & Protection

  • 47 pF Ceramic Disc Capacitors

    • References: C1, C2, C3
    • Quantity: 3
    • Package: Radial leaded disc, 5.0 mm lead spacing
    • Specifications: 47 pF, ±5%, 50 V or higher, C0G/NP0 dielectric
    • Electrical constraints: Oscillator tank circuit connected to U1 (74HCT04) and crystal Y1; C3 provides phase delay for the CLK2 signal.
    • Substitution latitude: Must be C0G/NP0 temperature-stable ceramic disc capacitors of 47 pF to maintain exact 6.25 MHz oscillation and memory clock phase margins.
    • User control: No.
    • Sourcing plan: distributor lookup: Vishay K470J15C0GF5TL2

  • 220 µF Radial Electrolytic Capacitor

    • Reference: C4
    • Quantity: 1
    • Package: Radial can, through-hole, 2.5 mm or 5.0 mm lead pitch, 6.3 mm to 8.0 mm diameter
    • Specifications: 220 µF, 25 V (or 16 V minimum), low ESR, polarized
    • Electrical constraints: Bulk power supply filter capacitor sitting directly across the 5.0 V power rail.
    • Substitution latitude: Any standard or low-ESR radial electrolytic capacitor rated ≥ 10 V and ≥ 220 µF fitting the through-hole footprint.
    • User control: No.
    • Sourcing plan: distributor lookup: Panasonic EEU-FC1E221

  • 100 nF (0.1 µF) Ceramic Bypass Capacitors

    • References: C5 through C44 (inclusive)
    • Quantity: 40
    • Package: Radial leaded disc/monolithic, 2.54 mm or 5.08 mm lead spacing
    • Specifications: 100 nF (marking code 104), 50 V, X7R dielectric
    • Electrical constraints: Dedicated high-frequency decoupling capacitors placed adjacent to the VCC pin of each logic IC across the 5.0 V bus.
    • Substitution latitude: Standard 100 nF X7R ceramic bypass capacitors with compatible pin spacing.
    • User control: No.
    • Sourcing plan: distributor lookup: Vishay K104K10X7RF5UH5

  • PTC Resettable Multifuse

    • Reference: F1
    • Quantity: 1
    • Package: Radial leaded disc, through-hole
    • Specifications: Hold current IH = 0.75 A, Trip current IT = 1.5 A, Maximum voltage VMAX = 60 V, Internal resistance R = 180 mΩ (Bourns MF-R075).
    • Reconciled discrepancy: Manual page 20 lists "hold 0.2A/trip 0.4A Multi-fuse", but the official BOM (bom.xlsx row 17) and schematic sheet 2/8 (page 49) explicitly specify Bourns MF-R075 (750 mA hold, 180 mΩ, 60 V). The authoritative BOM part number MF-R075 is preferred.
    • Electrical constraints: In-line overcurrent protection on the +5V USB input rail.
    • Substitution latitude: Any radial PTC resettable fuse with hold current between 0.5 A and 0.75 A and trip current ≤ 1.5 A rated for ≥ 6 V.
    • User control: No.
    • Sourcing plan: distributor lookup: Bourns MF-R075

  • 6.25 MHz Quartz Crystal

    • Reference: Y1
    • Quantity: 1
    • Package: HC-49/U through-hole (or low-profile HC-49/US)
    • Specifications: 6.250000 MHz fundamental frequency, load capacitance CL = 30 pF (or 32 pF), series resistance ESR ≤ 40 Ω
    • Electrical constraints: Driven by 74HCT04 inverter U1 in a Pierce oscillator configuration. System clock and horizontal/vertical VGA timing depend directly on this frequency (producing 31.25 kHz horizontal scan lines).
    • Substitution latitude: Must be 6.25 MHz fundamental crystal. Deviating in frequency alters VGA scan timings and baud rates.
    • User control: No.
    • Sourcing plan: distributor lookup: CTS MP062-E

Resistors & Resistor Networks

  • 1 MΩ Axial Resistor

    • Reference: R1
    • Quantity: 1
    • Package: Axial leaded, through-hole (0207, 1/4 W)
    • Specifications: 1 MΩ, 5% or 1%, 0.25 W carbon/metal film (Color code: Brown-Black-Green)
    • Electrical constraints: Oscillator feedback resistor across U1A.
    • Substitution latitude: Any 1 MΩ, 0.25 W through-hole resistor.
    • User control: No.
    • Sourcing plan: distributor lookup: Stackpole CF14JT1M00

  • 1 kΩ Axial Resistor

    • Reference: R2
    • Quantity: 1
    • Package: Axial leaded, through-hole (0207, 1/4 W)
    • Specifications: 1 kΩ, 5% or 1%, 0.25 W (Color code: Brown-Black-Red)
    • Electrical constraints: Oscillator damping resistor on U1A output.
    • Substitution latitude: Any 1 kΩ, 0.25 W through-hole resistor.
    • User control: No.
    • Sourcing plan: distributor lookup: Stackpole CF14JT1K00

  • 2.2 kΩ Axial Resistors

    • References: R3, R6, R7, R10, R19
    • Quantity: 5
    • Package: Axial leaded, through-hole (0207, 1/4 W)
    • Specifications: 2.2 kΩ, 5% or 1%, 0.25 W (Color code: Red-Red-Red)
    • Electrical constraints: R3 acts as LED current limiter; R6 and R7 are control unit bus pull-ups; R10 is audio output low-pass filter resistor; R19 is gamepad latch pull-up.
    • Substitution latitude: Any standard 2.2 kΩ, 0.25 W through-hole resistors.
    • User control: No.
    • Sourcing plan: distributor lookup: Stackpole CF14JT2K20

  • 68 Ω Axial Resistors

    • References: R17, R18
    • Quantity: 2
    • Package: Axial leaded, through-hole (0207, 1/4 W)
    • Specifications: 68 Ω, 5% or 1%, 0.25 W (Color code: Blue-Grey-Black)
    • Electrical constraints: VGA sync line series terminators for HSYNC and VSYNC driving 75 Ω monitor loads.
    • Substitution latitude: Standard 68 Ω to 75 Ω, 0.25 W through-hole resistors.
    • User control: No.
    • Sourcing plan: distributor lookup: Stackpole CF14JT68R0

  • 750 Ω Axial Resistors (VGA DAC High Bits)

    • References: R12, R14, R16
    • Quantity: 3
    • Package: Axial leaded, through-hole (0207, 1/4 W)
    • Specifications: 750 Ω, 5% or 1%, 0.25 W (Color code: Purple-Green-Brown)
    • Electrical constraints: Forms 2-bit-per-channel RGB weighted resistor DAC with 75 Ω video termination. Sits on high bits of OUT register U37 (74HCT377).
    • Substitution latitude: Must match DAC weighting for 74HCT driver levels (note: schematic indicates 390 Ω is used if subbing 74LS logic).
    • User control: No.
    • Sourcing plan: distributor lookup: Stackpole CF14JT750R

  • 1.5 kΩ Axial Resistors (VGA DAC Low Bits)

    • References: R11, R13, R15
    • Quantity: 3
    • Package: Axial leaded, through-hole (0207, 1/4 W)
    • Specifications: 1.5 kΩ, 5% or 1%, 0.25 W (Color code: Brown-Green-Red)
    • Electrical constraints: Low-bit resistors for RGB DAC. Sits on low bits of OUT register U37 (74HCT377).
    • Substitution latitude: Must match DAC ratio (schematic notes 820 Ω if subbing 74LS logic).
    • User control: No.
    • Sourcing plan: distributor lookup: Stackpole CF14JT1K50

  • 2.2 kΩ 5-Pin Resistor Arrays (SIP)

    • References: R4, R5, R8
    • Quantity: 3
    • Package: 5-pin SIP (Single In-line Package), through-hole, 2.54 mm pin pitch (Bourns 4605X-101-222LF)
    • Specifications: 2.2 kΩ bussed resistor network (4 common-bus resistors, pin 1 common).
    • Electrical constraints: Pull-up networks for control unit and blinkenlight LED arrays sitting on 5.0 V rail.
    • Substitution latitude: Any 5-pin bussed 2.2 kΩ SIP network with matching pinout (pin 1 common pin marked by dot).
    • User control: No.
    • Sourcing plan: distributor lookup: Bourns 4605X-101-222LF

  • 10 kΩ 6-Pin R2R Ladder Network (SIP)

    • Reference: R9
    • Quantity: 1
    • Package: 6-pin SIP, through-hole, 2.54 mm pin pitch (Bourns 4606X-R2R-103LF)
    • Specifications: 4-bit R-2R ladder network, R = 10 kΩ, 2R = 20 kΩ.
    • Electrical constraints: Passive 4-bit audio digital-to-analog converter driven by registers U38 (XOUT).
    • Substitution latitude: Standard 6-pin 4-bit R-2R SIP network with 10 kΩ resistance.
    • User control: No.
    • Sourcing plan: distributor lookup: Bourns 4606X-R2R-103LF

Diodes & Optoelectronics

  • 5.6 V 5 W Zener Diode

    • Reference: D1
    • Quantity: 1
    • Package: DO-15 (or DO-201) axial through-hole
    • Specifications: 5.6 V Zener breakdown, 5 W power dissipation, cathode band marking (1N5339B / 1N5339B-TP)
    • Electrical constraints: Shunt overvoltage protection clamped across +5V and GND directly after multifuse F1.
    • Substitution latitude: Any 5.6 V Zener diode rated ≥ 3 W to 5 W.
    • User control: No.
    • Sourcing plan: distributor lookup: Micro Commercial Components 1N5339B-TP

  • Schottky Signal Diodes (ROM / Instruction Matrix)

    • References: D3, D4, D9 through D36 (inclusive)
    • Quantity: 30
    • Package: DO-35 axial through-hole
    • Specifications: Low forward-voltage Schottky diode (BAT42 or 1N60P), VR ≥ 30 V, IF ≥ 100 mA, VF ≤ 0.4 V at 10 mA.
    • Electrical constraints: Forms diode-OR logic and instruction decode matrix for the control unit. Standard silicon diodes (e.g., 1N4148) have too high a forward voltage drop (0.7 V) and can violate TTL low-level logic thresholds (VOL ≤ 0.8 V).
    • Substitution latitude: Must be small-signal Schottky diodes (BAT42, BAT43, 1N60P, or BAT85). Ordinary silicon switching diodes (1N4148) should not be substituted.
    • User control: No.
    • Sourcing plan: distributor lookup: Vishay BAT42-TR

  • Red 3 mm LEDs

    • References: D2 (Power OK), D5, D6, D7, D8 (Blinkenlights)
    • Quantity: 5
    • Package: T-1 (3 mm / 3.15 mm) radial through-hole, tinted red diffused lens
    • Specifications: VF ≈ 1.8 V to 2.0 V, IF = 2 mA (low-current), luminous intensity ~2 mcd to 5 mcd
    • Electrical constraints: D2 indicates power rail stability; D5–D8 connect to extended output register U38 for CPU state/diagnostics.
    • Substitution latitude: Standard 3 mm red leaded LEDs (standard 2 mA or 20 mA types).
    • User control: No (indicators).
    • Sourcing plan: distributor lookup: Everlight HLMP1700C6A0

Active Integrated Circuits & Supervisory

All active ICs operate at a nominal VCC = 5.0 V DC.

  • Hex Inverter (74HCT04)

    • Reference: U1
    • Quantity: 1
    • Package: DIP-14 through-hole
    • Specifications: High-Speed CMOS with TTL-compatible inputs (74HCT series). Supply: 4.5 V to 5.5 V. Propagation delay ≤ 15 ns.
    • Electrical constraints: Used for Pierce crystal clock oscillator, clock buffering, and inversion.
    • Substitution latitude: Must be 74HCT04 (or 74AHCT04). Standard 74HC04 may fail to oscillate properly with TTL threshold biasing.
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT04N

  • Microprocessor Supervisory Circuit / Power-on Reset

    • Reference: U2
    • Quantity: 1
    • Package: TO-92-3 through-hole
    • Specifications: Active-low push-pull reset monitor, trip threshold = 4.50 V to 4.75 V, reset timeout delay ≈ 350 ms (MCP100-450DI/TO).
    • Electrical constraints: Pulls /RESET line low during power-up until 5V rail stabilizes, clearing program counters U3–U6 to address 0x0000.
    • Substitution latitude: Pin-compatible TO-92 supervisor with 4.50V/4.63V active-low push-pull output (e.g. MCP100-450, MCP100-460). Open-drain versions (e.g. MCP101) require a pull-up resistor.
    • User control: No.
    • Sourcing plan: distributor lookup: Microchip MCP100-450DI/TO

  • 4-Bit Presettable Binary Counters (74HCT161)

    • References: U3, U4, U5, U6 (Program Counter PC 0:15); U29, U30 (X Register 0:7)
    • Quantity: 6
    • Package: DIP-16 through-hole
    • Specifications: Synchronous 4-bit presettable binary counter with asynchronous reset. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Forms 16-bit program counter (PC) and 8-bit index/X register. Clocked at 6.25 MHz.
    • Substitution latitude: Must be 74HCT161 (e.g. CD74HCT161E or SN74HCT161N). Synchronous reset variants (74HCT163) are not compatible without timing changes.
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments CD74HCT161E

  • 1 Mbit (64K × 16) Parallel EPROM / OTP ROM

    • Reference: U7
    • Quantity: 1
    • Package: DIP-40 through-hole (0.6" wide)
    • Specifications: 64K words × 16-bit CMOS EPROM or OTP ROM, access time tACC ≤ 70 ns to 150 ns (AT27C1024-70PU or 27C1024), VCC = 5.0 V.
    • Electrical constraints: Program and microcode ROM. Access time must be fast enough for 6.25 MHz cycle (160 ns cycle period requires ≤ 100 ns or ≤ 150 ns access time).
    • Substitution latitude: Compatible with 27C1024, 27C2048 (in lower half), or pin-compatible flash/OTP equivalents (e.g. AT27C1024-70PU). Must be pre-programmed before installation.
    • User control: No.
    • Sourcing plan: distributor lookup: Microchip AT27C1024-70PU

  • Octal D-Type Flip-Flops with Clear (74HCT273)

    • References: U8 (Instruction Register IR), U9 (Data Register D), U38 (Extended Output Register XOUT)
    • Quantity: 3
    • Package: DIP-20 through-hole
    • Specifications: Octal D-type register with common clock and master reset. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Latches instruction words and video/audio output states.
    • Substitution latitude: 74HCT273 family (SN74HCT273N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT273N

  • Octal 3-State Bus Transceivers / Drivers (74HCT244)

    • References: U10, U28
    • Quantity: 2
    • Package: DIP-20 through-hole
    • Specifications: Non-inverting octal buffer/line driver with 3-state outputs. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Bus buffer for data bus and memory address interface.
    • Substitution latitude: 74HCT244 family (SN74HCT244N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT244N

  • Dual 2-to-4 Line Decoder / Demultiplexer (74HCT139)

    • Reference: U11
    • Quantity: 1
    • Package: DIP-16 through-hole
    • Specifications: Dual 2-to-4 line decoder/demux. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Control unit bus access decoding.
    • Substitution latitude: 74HCT139 family (SN74HCT139N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT139N

  • Dual 4-to-1 Multiplexers (74HCT153)

    • References: U12 (Condition Decoder), U17 through U24 (ALU Bits 0 through 7)
    • Quantity: 9
    • Package: DIP-16 through-hole
    • Specifications: Dual 4-line to 1-line data selector/multiplexer. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Forms 8 bits of the central Arithmetic Logic Unit (ALU) logic operations (AND, OR, XOR, LD) and branch condition evaluation.
    • Substitution latitude: 74HCT153 family (CD74HCT153E).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments CD74HCT153E

  • 3-to-8 Line Decoders / Demultiplexers (74HCT138)

    • References: U13 (Addressing Mode Decoder), U14 (Instruction Decoder)
    • Quantity: 2
    • Package: DIP-16 through-hole
    • Specifications: 3-line to 8-line decoder/demux with enable pins. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Microcode opcode decoding.
    • Substitution latitude: 74HCT138 family (SN74HCT138N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT138N

  • Octal Inverting Bus Buffers (74HCT240)

    • Reference: U15
    • Quantity: 1
    • Package: DIP-20 through-hole
    • Specifications: Octal buffer/line driver with inverting 3-state outputs. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Inverters for control signals in the control unit.
    • Substitution latitude: 74HCT240 family (SN74HCT240N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT240N

  • Quad 2-Input OR Gate (74HCT32)

    • Reference: U16
    • Quantity: 1
    • Package: DIP-14 through-hole
    • Specifications: Quad 2-input positive-OR gates. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Control path logic and gate decoding.
    • Substitution latitude: 74HCT32 family (CD74HCT32EE4).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments CD74HCT32EE4

  • 4-Bit Binary Full Adders (74HCT283)

    • References: U25, U26
    • Quantity: 2
    • Package: DIP-16 through-hole
    • Specifications: 4-bit binary full adder with fast internal carry look-ahead. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Cascaded to form the 8-bit arithmetic adder/subtractor core for the ALU.
    • Substitution latitude: Must be 74HCT283 (e.g. CD74HCT283E). Standard 74HC283 or 74LS283 can create speed/level mismatch.
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments CD74HCT283E

  • Octal D-Type Flip-Flops with Data Enable (74HCT377)

    • References: U27 (Accumulator AC), U31 (Y Register), U37 (Output Register OUT)
    • Quantity: 3
    • Package: DIP-20 through-hole
    • Specifications: Octal D-type flip-flop with clock enable (/EN). High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Primary internal registers (Accumulator AC, Y address pointer, OUT display/audio register).
    • Substitution latitude: 74HCT377 family (SN74HCT377N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT377N

  • Quad 2-to-1 Data Selectors / Multiplexers (74HCT157)

    • References: U32, U33 (High Address Selectors), U34, U35 (Low Address Selectors)
    • Quantity: 4
    • Package: DIP-16 through-hole
    • Specifications: Quad 2-line to 1-line non-inverting multiplexer. High-speed CMOS, TTL-compatible. VCC = 5.0 V.
    • Electrical constraints: Routes SRAM 15-bit address bus between program counter, registers, and instruction operands.
    • Substitution latitude: 74HCT157 family (SN74HCT157N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HCT157N

  • 32K × 8 Static RAM (62256)

    • Reference: U36
    • Quantity: 1
    • Package: DIP-28 through-hole (0.6" wide)
    • Specifications: 256 Kbit (32,768 words × 8-bit) static RAM, access time ≤ 55 ns to 70 ns, low power CMOS, VCC = 5.0 V (Lyontek LY62256PL-55LLI).
    • Electrical constraints: Main system memory. Single-cycle read/write access requires ≤ 70 ns speed grade (55 ns strongly recommended for 6.25 MHz timing margins).
    • Substitution latitude: Any industry-standard 62256 (or 62C256) 32Kx8 SRAM in 28-pin 600-mil DIP package rated ≤ 70 ns.
    • User control: No.
    • Sourcing plan: distributor lookup: Lyontek LY62256PL-55LLI

  • 8-Bit Serial-In / Parallel-Out Shift Register (74HC595)

    • Reference: U39
    • Quantity: 1
    • Package: DIP-16 through-hole
    • Specifications: 8-bit shift register with 8-bit storage register and 3-state outputs. High-speed CMOS (74HC series). VCC = 5.0 V.
    • Electrical constraints: Serial-to-parallel shift register deserializing button pulses from gamepad J4.
    • Substitution latitude: 74HC595 or 74HCT595 (SN74HC595N).
    • User control: No.
    • Sourcing plan: distributor lookup: Texas Instruments SN74HC595N

Connectors & Sockets

  • Mini-USB Type-B Receptacle

    • Reference: J1
    • Quantity: 1
    • Package: Mini-USB Type-B Female, right-angle, hybrid through-hole/SMD (Molex 54819-0519)
    • Electrical constraints: 5.0 V power input only (pins 1 and 5 used; data pins unconnected).
    • Substitution latitude: Any PCB-mount Mini-USB Type-B receptacle matching the Molex 54819-0519 footprint.
    • User control: Yes (cable insertion).
    • Sourcing plan: distributor lookup: Molex 54819-0519

  • 3.5 mm Stereo Audio Jack

    • Reference: J2
    • Quantity: 1
    • Package: 3.5 mm stereo audio jack, right-angle through-hole, 3-pin or 5-pin (CUI Devices / Same Sky SJ1-3523N)
    • Electrical constraints: Line-level audio output driven by R2R ladder DAC R9.
    • Substitution latitude: CUI SJ1-3523N, SJ1-3524N, SJ1-3525N or equivalent 3.5 mm phone jacks matching footprint.
    • User control: Yes (audio jack plug).
    • Sourcing plan: distributor lookup: Same Sky (formerly CUI) SJ1-3523N

  • 15-Pin High-Density D-SUB Female Receptacle (VGA)

    • Reference: J3
    • Quantity: 1
    • Package: 15-pin 3-row high-density D-sub female, right-angle PCB through-hole with threaded mounting hex standoffs / ground boardlocks (Amphenol L77HDE15SD1CH4R)
    • Electrical constraints: Standard analog RGB VGA video output.
    • Substitution latitude: Industry standard right-angle through-hole VGA female connector (footprint standard 8.08 mm or 8.89 mm footprint depth).
    • User control: Yes (monitor cable connector).
    • Sourcing plan: distributor lookup: Amphenol L77HDE15SD1CH4R

  • 9-Pin D-SUB Male Receptacle (Gamepad Port)

    • Reference: J4
    • Quantity: 1
    • Package: 9-pin 2-row D-sub male, right-angle PCB through-hole with boardlocks (TE Connectivity 5747840-3)
    • Electrical constraints: Serial interface to NES/Famicom clone gamepad (or Pluggy McPlugface adapter).
    • Substitution latitude: Standard DB9 male right-angle through-hole PCB connector.
    • User control: Yes (gamepad plug).
    • Sourcing plan: distributor lookup: TE Connectivity 5747840-3

  • 40-Pin DIP IC Socket

    • Reference: Socket for U7
    • Quantity: 1
    • Package: 40-pin DIP socket, 0.600" (15.24 mm) row pitch, 2.54 mm pin pitch
    • Electrical constraints: Houses 27C1024 EPROM.
    • Substitution latitude: Standard stamped or machined pin 40-pin DIP socket.
    • User control: No.
    • Sourcing plan: distributor lookup: On-Shore Technology ED40DT

  • 28-Pin DIP IC Socket

    • Reference: Socket for U36
    • Quantity: 1
    • Package: 28-pin DIP socket, 0.600" (15.24 mm) row pitch, 2.54 mm pin pitch
    • Electrical constraints: Houses 62256 SRAM.
    • Substitution latitude: Standard stamped or machined pin 28-pin DIP socket (600 mil wide).
    • User control: No.
    • Sourcing plan: distributor lookup: Assmann WSW AR-28-HZL-TT

Mechanical, Hardware & Accessories

  • Gigatron Main Printed Circuit Board

    • Reference: PCB
    • Quantity: 1
    • Package: Custom bare PCB (2-layer FR4, lead-free HASL finish, green solder mask, silkscreen on top)
    • Electrical constraints: Carries all 5V power routing, 6.25 MHz clock distribution, 16-bit address and 8-bit data buses.
    • Substitution latitude: Must be fabricated from official KiCad layout files (Gigatron.sch, Gigatron.kicad_pcb).
    • User control: No.
    • Sourcing plan: general web research: "Gigatron TTL microcomputer Gerber PCB files"

  • USB Power Cable

    • Reference: Cable
    • Quantity: 1
    • Specifications: USB Type-A Male to Mini-USB Type-B Male cable, 28 AWG power conductors, length ~1 m (Qualtek 3021055-03)
    • Electrical constraints: Must supply 5.0 V regulated DC from external 5V 1A+ USB wall charger.
    • Substitution latitude: Standard Mini-USB charging/data cable.
    • User control: Yes (connecting power).
    • Sourcing plan: distributor lookup: Qualtek 3021055-03

  • EPROM UV Window Protection Label

    • Reference: Label
    • Quantity: 1
    • Specifications: Opaque silver/gold foil adhesive label, 25.4 mm × 10 mm (TE Connectivity 12100)
    • Electrical constraints: Blocks ambient UV light from erasing windowed EPROM silicon die.
    • Substitution latitude: Any opaque light-blocking foil sticker or electrical tape.
    • User control: No.
    • Sourcing plan: distributor lookup: TE Connectivity 12100

  • Famicom-Style Clone Gamepad Controller

    • Reference: Gamepad
    • Quantity: 1
    • Specifications: 8-button NES/Famicom clone gamepad with 9-pin sub-D female connector wiring (shift register based: Clock, Latch, Data, +5V, GND).
    • Electrical constraints: 5V logic interface. Note from manual: standard Atari 9-pin joysticks are incompatible; pinout requires Famicom/NES serial shift-register style controller.
    • Substitution latitude: Famicom/Subor DB9 clone gamepad controller.
    • User control: Yes (primary operator input device: directional pad, Select, Start, A, B buttons).
    • Sourcing plan: retail shopping search: "Famicom clone gamepad DB9 9 pin"

  • Gigatron Wooden Enclosure & Acrylic Faceplate

    • Reference: Enclosure
    • Quantity: 1
    • Specifications: Custom laser-cut/machined hardwood frame with clear acrylic (Plexiglas) top cover.
    • Reconciled discrepancy: bom.xlsx row 51 explicitly notes "custom made, no longer available". Original production stopped in 2020.
    • Substitution latitude: Custom laser cut / 3D printed enclosure based on open-source vector drawings, or operated as bare PCB.
    • User control: Yes (chassis).
    • Sourcing plan: general web research: "Gigatron TTL wooden case DXF laser cut drawings"

  • Self-Adhesive Rubber Bumpons / Feet

    • Reference: Rubber feet
    • Quantity: 8
    • Specifications: 3M Bumpon protective products, hemispherical clear polyurethane feet, 7.9 mm diameter × 5.6 mm height (3M SJ-5302). 4 placed on outer casing, 4 placed under PCB corners.
    • Substitution latitude: Any 7 mm to 10 mm self-adhesive rubber/silicone bumper feet.
    • User control: No.
    • Sourcing plan: distributor lookup: 3M SJ-5302-CLEAR

  • Assembly & User Manual

    • Reference: Manual
    • Quantity: 1
    • Specifications: Full-color printed manual, Wire-O bound, 59 pages.
    • Substitution latitude: PDF printable locally from open-source release (CC BY-SA 4.0).
    • User control: No.
    • Sourcing plan: retail shopping search: "print spiral bound document A4"

Pluggy McPlugface (PS/2 Keyboard Daughterboard)

  • Pluggy McPlugface PCB

    • Reference: Daughterboard PCB
    • Quantity: 1
    • Package: Small 2-layer FR4 bare PCB, lead-free HASL finish
    • Substitution latitude: Must be fabricated from official hardware files (https://gigatron.io/pluggy).
    • User control: No.
    • Sourcing plan: general web research: "Pluggy McPlugface Gerber PCB files"

  • 6-Pin Mini-DIN PS/2 Female Receptacle

    • Reference: J1 (Pluggy)
    • Quantity: 1
    • Package: 6-pin Mini-DIN female, right-angle through-hole, shielded (Kycon KMDGX-6S-AS)
    • Electrical constraints: Standard 5.0 V PS/2 keyboard interface (Clock and Data lines with 5V power).
    • Substitution latitude: Any right-angle PCB-mount 6-pin Mini-DIN PS/2 female connector.
    • User control: Yes (keyboard cable insertion).
    • Sourcing plan: distributor lookup: Kycon KMDGX-6S-AS

  • 9-Pin D-SUB Female Receptacle

    • Reference: J2 (Pluggy)
    • Quantity: 1
    • Package: 9-pin 2-row D-sub female, right-angle through-hole (Amphenol L77SDE09SOL2)
    • Electrical constraints: Plugs directly into the Gigatron mainboard gamepad port J4.
    • Substitution latitude: Standard DB9 female right-angle PCB connector.
    • User control: Yes (plugging adapter into mainboard).
    • Sourcing plan: distributor lookup: Amphenol L77SDE09SOL2

  • 8-Bit AVR Microcontroller (ATtiny85)

    • Reference: U1 (Pluggy)
    • Quantity: 1
    • Package: DIP-8 through-hole (0.3" row pitch)
    • Specifications: Microchip/Atmel ATtiny85-20PU, 8-bit AVR RISC microcontroller, 8 KB internal flash, 512 B SRAM, 512 B EEPROM, running at 8 MHz internal RC oscillator, VCC = 5.0 V.
    • Electrical constraints: Powered from 5.0 V bus of mainboard port J4. Translates PS/2 scancodes into controller signals; transfers Tiny BASIC image into Gigatron RAM via controller port.
    • Substitution latitude: ATtiny85-20PU (or ATtiny45-20PU if flash capacity allows, though 8 KB is required for BabelFish and embedded Tiny BASIC). Must be programmed with BabelFish firmware before use.
    • User control: No.
    • Sourcing plan: distributor lookup: Microchip ATtiny85-20PU

  • 8-Pin DIP IC Socket

    • Reference: Socket for U1 (Pluggy)
    • Quantity: 1
    • Package: 8-pin DIP socket, 0.300" (7.62 mm) row pitch, 2.54 mm pin pitch (Mill-Max 110-47-308-41-001000)
    • Substitution latitude: Standard 8-pin DIP socket.
    • User control: No.
    • Sourcing plan: distributor lookup: Mill-Max 110-47-308-41-001000

Software and network dependencies

  • Gigatron Microcode & System ROM Image (gigatron-rom)

    • Name: Gigatron System ROM (contains TTL CPU instruction dispatch microcode, video/audio output loop, vCPU 16-bit virtual machine interpreter, font table, and preloaded applications: Snake, Racer, Mandelbrot, Pictures, Credits, Loader, Tetronis, Bricks, Tic-Tac-Toe, Tiny BASIC, WozMon / Apple-1 emulator, MS BASIC).
    • Origin: https://github.com/kervinck/gigatron-rom
    • Version: Stated in documentation as ROM v1, ROM v2, ROM v3, ROM v4, ROM v5, and DEVROM. The assembly manual specifies that ROM v3 or newer is required to support saving programs to the PS/2 adapter; ROM v4/v5 includes additional games, high-resolution pictures, and WozMon.
    • Where the version came from: stated in documentation
    • Whether versions are pinned at all: Not pinned. The sources point to the repository default branch without specifying a git commit SHA or tagged release lockfile.
    • Manifest location: Not applicable (binary firmware burned into physical 27C1024 EPROM).
    • Network exposure: not stated in the sources (the device has no network hardware, Ethernet, Wi-Fi, or IP stack).
    • Check plan: not checkable: vendor firmware with no package ecosystem or CVE advisory database.

  • Pluggy McPlugface Keyboard Bridge Firmware ("BabelFish")

    • Name: BabelFish ATtiny85 Firmware (PS/2 keyboard protocol handler, scancode translator for US, GB, DE, FR, IT, ES layouts, and serial loader sending embedded Tiny BASIC v2 over the gamepad interface).
    • Origin: https://github.com/kervinck/gigatron-rom/tree/master/Utils/BabelFish
    • Version: not stated
    • Where the version came from: not stated
    • Whether versions are pinned at all: Unpinned (tracked in the gigatron-rom repository without a separate release manifest).
    • Manifest location: Not applicable (binary hex image burned into ATtiny85 microcontroller).
    • Network exposure: not stated in the sources (local serial interface only).
    • Check plan: not checkable: bare-metal microcontroller firmware with no advisory database.

Remaining Temporal Dependencies

External URLs and Documentation

  • Primary website: https://gigatron.io/ and https://gigatronttl.eu/
  • Community forum: https://forum.gigatronttl.eu/
  • Hardware walkthrough: https://gigatronttl.eu/walkthrough
  • Hardware troubleshooting: https://gigatronttl.eu/diagnostics
  • Firmware & tools repository: https://github.com/kervinck/gigatron-rom

Fabrication Specifications

  • Main Board PCB:
    • Layers: 2 copper layers
    • Substrate: FR-4, 1.6 mm thickness
    • Surface Finish: Lead-free HASL
    • Dimensions: Approximately 240 mm × 170 mm
    • Hole Pitch: Standard 2.54 mm (0.1") through-hole DIP grid
    • Design files: KiCad project available at https://gigatron.io/pcb
  • Pluggy McPlugface PCB:
    • Layers: 2 copper layers
    • Dimensions: Approximately 40 mm × 30 mm
    • Design files: Available at https://gigatron.io/pluggy
  • Enclosure:
    • Material: Laser-cut wooden perimeter frame with clear cast acrylic lid.
    • Status: Out of production as a pre-packaged kit item since 2020; CAD/laser vector files are open-source for custom fabrication.