2 layers144.8 × 73.9 mm
Control
Robert-Riordan-UCD/8_Bit_CPU_PCB
PCB version of Ben Eaters 8-bit breadboard computer
68 partsCERN-OHL-P-2.0
2 layers109.7 × 49.5 mm
8 Bit CPU PCB
Robert-Riordan-UCD/8_Bit_CPU_PCBPCB version of Ben Eaters 8-bit breadboard computer
- Size
- 109.7 × 49.5 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 19
- Nets
- 52
- Pads
- 140
- Tracks, vias
- 155, 1
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 22 Jul 2024
- Updated
- 15 Jan 2025
Overview
8 Bit CPU PCB is an open-source printed circuit board by Robert-Riordan-UCD, from the Robert-Riordan-UCD/8_Bit_CPU_PCB repository on GitHub, published under the CERN-OHL-P-2.0 licence. It is a 2-layer board of 109.7 × 49.5 mm with 19 parts on 52 nets, routed with 155 tracks and 1 via.
It is built around the 74LS173SC, AT28C64B-15PI and CD74HCT139E, with the CD74HCT73E and NE555P among its other parts. Its parts include 7 ICs, 3 capacitors, 3 resistors and 2 connectors. It belongs with the retro computing and games boards of this library.
Main components
574LS173SC
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
AT28C64B-15PI
PDIP-28-40℃~+85℃ 10 years 100,000 cycles 10ms 4.5V~5.5V 64Kbit Hardware write protection function、Software write protection function、Page write protection function Parallel Port (Parallel) PDIP-28 EEPROMMicrochip TechnologyEEPROM
CD74HCT139E
PDIP-16-55℃~+125℃ 4.5V~5.5V 4mA 4mA 51ns@4.5V,50pF 8uA Decoder HCT Level shifting Single Supply PDIP-16 Signal Switches, Multiplexers, Decoders ROHSTexas InstrumentsSignal Switches, Multiplexers, Decoders
CD74HCT73E
PDIP-14-55℃~+125℃ 1 10pF 2 38ns@4.5V,50pF 4.5V~5.5V 4mA 4mA 4uA 60MHz 74HCT Series Complementary Falling Edge JK-Type Reset PDIP-14 Flip Flops ROHSTexas InstrumentsFlip Flops
NE555P
DIP-80℃~+70℃ 100kHz 10mA 4.5V~16V DIP-8 555 Timers / Counters ROHSTexas InstrumentsTimers / Counters
README
README.md8-Bit PCB CPU
This is my version of Ben Eaters 8-bit breadboard SAP-1 CPU, converted to a PCB. I have made some minor changes as I could not find all of the components as listed in Ben's part list.
Video of the computer running
https://youtube.com/shorts/QNcSWgcGv9o?si=QzoUVq9Kj8X1f4Rs
Major Changes
Random Access Memory
- RAM IC's have been replaced with ATMega328-PU's. This should allow me to have persistant programs between power cycles.
License
CERN Open Hardware Licence Version 2 - Permissive
Parts
19| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | 0.01u | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C2, C3 |
| 2 | 1k | _DownloadFootprints:CF_series_Resistors_THT | R2, R3 |
| 2 | 74LS173 | Package_DIP:DIP-16_W7.62mm | U1, U2 |
| 1 | 0.1uF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C1 |
| 1 | 100k | _DownloadFootprints:CF_series_Resistors_THT | R1 |
| 1 | AT28C64B-15PI | _DownloadFootprints:eeprom | U3 |
| 1 | CC56-12CGKWA | Display_7Segment:CA56-12CGKWA | U4 |
| 1 | CD74HCT139E | _DownloadFootprints:2x_2_to_4_demux | U6 |
| 1 | CD74HCT73E | _DownloadFootprints:2x_JK_FF | U7 |
| 1 | Conn_01x04_Pin | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | J2 |
| 1 | Conn_01x10_Pin | Connector_PinHeader_2.54mm:PinHeader_1x10_P2.54mm_Vertical | J1 |
| 1 | NE555P | Package_DIP:DIP-8_W7.62mm | U5 |
The 15 most common of 19 parts.
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Questions
How big is the 8 Bit CPU PCB PCB?
It measures 109.7 × 49.5 mm and has 2 copper layers, 1.6 mm thick.
What parts does the 8 Bit CPU PCB use?
19 parts, built around the 74LS173SC, AT28C64B-15PI, CD74HCT139E and CD74HCT73E. 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 8 Bit CPU PCB KiCad files?
From the Robert-Riordan-UCD/8_Bit_CPU_PCB repository on GitHub, at the commit this page was made from: the board is Output/Output.kicad_pcb and its schematic ALU/ALU.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the 8 Bit CPU PCB design in my own project?
Its repository publishes it under the CERN-OHL-P-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).