4 layers98.8 × 50.1 mm
4 layers82.7 × 41.5 mm
Instruction register
georgesleen/8-BitComputerRepo to track my 8-bit computer progress
- Size
- 82.7 × 41.5 mm
- Copper layers
- 4
- Thickness
- 1.6 mm
- Parts
- 45
- Nets
- 54
- Pads
- 202
- Tracks, vias
- 549, 35
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 14 Jun 2024
- Updated
- 17 Sep 2025
Overview
Instruction register is an open-source printed circuit board by georgesleen, from the georgesleen/8-BitComputer repository on GitHub. It is a 4-layer board of 82.7 × 41.5 mm with 45 parts on 54 nets, routed with 549 tracks and 35 vias.
It is built around the 74LS245SC and 74LS173SC. Its parts include 16 resistors, 16 diodes, 6 ICs, 5 connectors and 2 capacitors. It belongs with the retro computing and games boards of this library.
Main components
274LS245SC
-0℃~+70℃ 12ns@5V,45pF 15mA 24mA 4.75V~5.25V 74LS 8 Bidirectional Output enable Schmitt trigger Tri-State - Buffers, Drivers, Receivers, Transceivers ROHSTexas InstrumentsBuffers, Drivers, Receivers, Transceivers74LS173SC
CDIP-160℃~+70℃ 10ns 10ns 28mA 30MHz 4 4.75V~5.25V 40ns@5V,15pF 74LS Series Asynchronous D-Type Reset Rising Edge Tri-State CDIP-16 Flip FlopsTexas InstrumentsFlip Flops
README
README.mdCustom 8-Bit Computer
Repository showcasing a simple 8 bit computer built around the 7400 series ICs.
Heavily inspired by Ben Eater's 8-Bit computer series on youtube, with additional support from Digital Computer Electronics by Albert Paul Malvino
Parts
45| Qty | Value | Footprint | References |
|---|---|---|---|
| 16 | 220 | Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16 |
| 16 | LED | LED_SMD:LED_1206_3216Metric_Pad1.42x1.75mm_HandSolder | D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, D14, D15, D16 |
| 4 | 74LS173 | Package_DIP:DIP-16_W7.62mm_Socket_LongPads | U1, U3, U4, U5 |
| 2 | 0.1 uF | Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C1, C2 |
| 2 | 74LS245 | Package_DIP:DIP-20_W7.62mm_Socket_LongPads | U2, U6 |
| 1 | BUS LB | Connector_Molex:Molex_PicoBlade_53048-0810_1x08_P1.25mm_Horizontal | J3 |
| 1 | BUS UB | Connector_Molex:Molex_PicoBlade_53048-0810_1x08_P1.25mm_Horizontal | J4 |
| 1 | Control | Connector_Molex:Molex_PicoBlade_53048-0210_1x02_P1.25mm_Horizontal | J2 |
| 1 | Instruction Out | Connector_Molex:Molex_PicoBlade_53048-0810_1x08_P1.25mm_Horizontal | J5 |
| 1 | Power | Connector_Molex:Molex_PicoBlade_53048-0410_1x04_P1.25mm_Horizontal | J1 |
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Questions
How big is the Instruction register PCB?
It measures 82.7 × 41.5 mm and has 4 copper layers, 1.6 mm thick.
What parts does the Instruction register use?
45 parts, built around the 74LS245SC and 74LS173SC. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Instruction register KiCad files?
From the georgesleen/8-BitComputer repository on GitHub, at the commit this page was made from: the board is Schematics/Instruction register/Instruction register.kicad_pcb and its schematic Schematics/ALU/ALU V1.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Instruction register design in my own project?
Its repository states no licence, so its author keeps all rights: ask georgesleen before reusing the design.