Readiness: Gigatron TTL Microcomputer
Verdict: Ready with caveats · 2026-07-19 · est. parts cost $115–$140
The Gigatron TTL remains buildable as of July 2026 but requires multi-vendor sourcing and DIY enclosure fabrication. The core logic components and passives are widely available, and the sourcing status for the 32K SRAM has improved since the last report due to stabilized stock of recommended substitutes. However, the 6.25 MHz crystal and the specific 16-bit EPROM remain niche items that require procurement from secondary distributors (Mouser) to ensure adequate stock. The verdict remains "Ready with caveats" as the system still requires manual firmware programming and custom case fabrication.
Action required
| Part |
Problem |
Recommended action |
| 74HCT04 |
Out of stock at primary distributor (DigiKey). |
Source SN74HCT04N from Mouser or use CD74HCT04E from DigiKey. |
| 62256 |
Lyontek LY62256PL-55LLI is confirmed obsolete. |
Use Alliance AS6C62256-55PCN as a direct substitute. |
| Quartz Crystal |
6.25 MHz (MP062-E) is out of stock at primary (DigiKey). |
Source MP062-E from Mouser. |
| DB9 Male |
5747840-3 is out of stock at primary (DigiKey). |
Use Assmann A-DS 09 A/KG-T2S as a direct substitute. |
| Wooden Enclosure |
Commercial manufacturing has ceased. |
Download SVG or OpenSCAD plans from gigatron.io for DIY laser cutting or woodworking. |
Parts
1. Integrated Circuits (Main Board)
| Part |
Spec/Package |
Status |
Stock |
Price |
Source |
Drift |
| 74HCT04 |
Hex Inverter, DIP-14 |
Available |
1,443 |
$0.88 |
Mouser |
+$0.20 |
| 74HCT161 |
4-bit Counter, DIP-16 |
Ready |
9,661 |
$1.34 |
DigiKey |
0 |
| 74HCT273 |
Octal Register, DIP-20 |
Ready |
26,627 |
$0.93 |
DigiKey |
0 |
| 74HCT244 |
Octal Bus Driver, DIP-20 |
Ready |
4,467 |
$1.52 |
DigiKey |
0 |
| 74HCT139 |
Dual 2-to-4 Decoder, DIP-16 |
Ready |
26,330 |
$1.19 |
DigiKey |
0 |
| 74HCT153 |
Dual 4-to-1 MUX, DIP-16 |
Ready |
816 |
$1.22 |
DigiKey |
0 |
| 74HCT138 |
3-to-8 Decoder, DIP-16 |
Ready |
3,421 |
$0.89 |
DigiKey |
0 |
| 74HCT240 |
Octal Inv Buffer, DIP-20 |
Ready |
24,075 |
$0.96 |
DigiKey |
0 |
| 74HCT32 |
Quad OR Gate, DIP-14 |
Ready |
1,773 |
$0.97 |
DigiKey |
0 |
| 74HCT283 |
4-bit Full Adder, DIP-16 |
Ready |
915 |
$1.32 |
DigiKey |
0 |
| 74HCT377 |
Octal Flip-Flop, DIP-20 |
Ready |
10,109 |
$1.43 |
DigiKey |
0 |
| 74HCT157 |
Quad 2-to-1 MUX, DIP-16 |
Ready |
33,781 |
$1.16 |
DigiKey |
0 |
| 74HC595 |
8-bit Shift Reg, DIP-16 |
Ready |
14,290 |
$1.86 |
DigiKey |
0 |
| 62256 |
32K x 8 SRAM, DIP-28 |
Obsolete |
0 |
— |
— |
— |
| 27C1024 |
1Mbit EPROM, DIP-40 |
Low Stock |
96 |
$4.52 |
DigiKey |
0 |
| MCP100-450DI/TO |
Reset IC, TO-92 |
Ready |
8,796 |
$0.42 |
DigiKey |
0 |
2. Pluggy McPlugface (Add-on) ICs
| Part |
Spec/Package |
Status |
Stock |
Price |
Source |
Drift |
| ATtiny85-20PU |
MCU, DIP-8 |
Ready |
24,959 |
$1.66 |
DigiKey |
0 |
3. Passive Components (Main Board)
| Part |
Spec/Package |
Status |
Stock |
Price |
Source |
Drift |
| Resistor 68 Ω |
Axial, 1/4W |
Ready |
21,278 |
$0.10 |
DigiKey |
0 |
| Resistor 750 Ω |
Axial, 1/4W |
Ready |
20,714 |
$0.10 |
DigiKey |
0 |
| Resistor 1 kΩ |
Axial, 1/4W |
Ready |
710,261 |
$0.10 |
DigiKey |
0 |
| Resistor 1.5 kΩ |
Axial, 1/4W |
Ready |
26,620 |
$0.10 |
DigiKey |
0 |
| Resistor 2.2 kΩ |
Axial, 1/4W |
Ready |
25,751 |
$0.10 |
DigiKey |
0 |
| Resistor 1 MΩ |
Axial, 1/4W |
Ready |
534,545 |
$0.10 |
DigiKey |
0 |
| Resistor Array |
5-pin SIP, 2.2 kΩ |
Low Stock |
32 |
$0.28 |
DigiKey |
0 |
| R2R Network |
6-pin SIP, 10 kΩ |
Ready |
1,368 |
$0.46 |
DigiKey |
0 |
| Capacitor 47 pF |
Ceramic, 50V |
Ready |
24,936 |
$0.26 |
DigiKey |
0 |
| Capacitor 100 nF |
Ceramic, 50V |
Ready |
233,541 |
$0.28 |
DigiKey |
+$0.01 |
| Capacitor 220 µF |
Electrolytic, 25V |
Ready |
7,495 |
$0.60 |
DigiKey |
0 |
4. Discrete Semiconductors and Protection
| Part |
Spec/Package |
Status |
Stock |
Price |
Source |
Drift |
| Signal Diode |
BAT42, DO-35 |
Ready |
23,133 |
$0.50 |
DigiKey |
0 |
| Zener Diode |
5.6V 5W, DO-15 |
Ready |
67,621 |
$1.26 |
DigiKey |
0 |
| LED Red, 3mm |
1.8V, 2mA |
Ready |
60,765 |
$0.51 |
DigiKey |
0 |
| Multifuse (PTC) |
0.75A 60V, Radial |
Ready |
4,604 |
$0.47 |
DigiKey |
0 |
| Quartz Crystal |
6.25 MHz, HC-49/U |
Available |
1,007 |
$1.01 |
Mouser |
— |
5. Connectors and Hardware
| Part |
Spec/Package |
Status |
Stock |
Price |
Source |
Drift |
| Mini-USB |
Type B, 5-pin |
Ready |
901 |
$2.07 |
DigiKey |
0 |
| 3.5mm Audio Jack |
Stereo, TH |
Ready |
234,430 |
$1.06 |
DigiKey |
0 |
| DB15 Female (VGA) |
High Density, R/A |
Low Stock |
114 |
$2.07 |
DigiKey |
0 |
| DB9 Male |
Standard, R/A |
Available |
18,130 |
$2.87 |
TTI |
— |
| Mini-DIN 6-pin |
PS/2, TH |
Ready |
4,184 |
$1.88 |
DigiKey |
0 |
| DB9 Female |
Standard, TH |
Ready |
1,465 |
$1.24 |
DigiKey |
0 |
| IC Sockets |
DIP Assortment |
Ready |
High |
$1.95 |
eBay |
-$4.05 |
| Famicom Gamepad |
Clone, DB9 |
Ready |
High |
$4.95 |
AliExpress |
0 |
| Wooden Enclosure |
Custom Case |
Obsolete |
— |
— |
— |
— |
| Rubber Feet |
3M Bumpons |
Ready |
250,992 |
$14.70 |
DigiKey |
0 |
Substitutes
Verify any substitute against its datasheet before ordering.
Other dependencies
- Main ROM: Requires 27C1024 EPROM programmed with Gigatron ROM v5. (Verified at kervinck/gigatron-rom GitHub)
- BabelFish Firmware: Requires ATtiny85 programmed with BabelFish interface software. (Verified at kervinck/gigatron-rom Utils)
- PCB Fabrication: Requires Gerber files for Main and Pluggy boards from gigatron.io. (Verified)
- Enclosure Plans: DIY OpenSCAD/SVG files available via gigatron.io FAQ for custom fabrication. (Verified)
Watch list
- AT27C1024-70PU: Only 96 units remain at primary distributor. While 622 units exist at Mouser, this part is high-risk for future availability.
- 6.25 MHz Crystal: No stock at primary distributor; Mouser stock is stable but requires separate shipping.
- Resistor Array (4605X-101-222LF): Extremely low stock (32 units) at DigiKey. Source from Newark (8,000+ available) if primary stock fails.
- DB15 Female (L77HDE15SD1CH4R): Low stock (114 units) at DigiKey. Monitor Newark stock as a secondary source.