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 layers133 × 58.5 mm
PCB version of Ben Eaters 8-bit breadboard computer
- Size
- 133 × 58.5 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 61
- Nets
- 92
- Pads
- 270
- Tracks, vias
- 468, 1
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 22 Jul 2024
- Updated
- 15 Jan 2025
Overview
RAM 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 133 × 58.5 mm with 61 parts on 92 nets, routed with 468 tracks and 1 via.
It is built around the ATMEGA328-PU, SN74HCT245N and CD74HCT258E, with the B3U-1000P among its other parts. Its parts include 20 resistors, 9 capacitors, 9 connectors, 8 ICs and 8 diodes. It belongs with the retro computing and games boards and the AVR (ATmega, ATtiny) boards of this library.
Main components
4
ATMEGA328-PU
PDIP-28-40℃~+85℃ 1.8V~5.5V 10bit 1KB 20MHz 23 2KB 32KB 8 Bit AVR Built-in FLASH PDIP-28 Microcontrollers (MCU/MPU/SOC) ROHSMicrochip TechnologyMicrocontrollers (MCU/MPU/SOC)
SN74HCT245N
DIP-20-40℃~+85℃ 1 14ns@5.5V,50pF 4.5V~5.5V 6mA 6mA 74HCT 8 80uA Bidirectional Tri-State DIP-20 Buffers, Drivers, Receivers, Transceivers ROHSTexas InstrumentsBuffers, Drivers, Receivers, Transceivers
CD74HCT258E
PDIP-16-55℃~+125℃ 27ns@4.5V,50pF 4.5V~5.5V 6mA 6mA 74HCT 8uA Output enable high-impedance、Tri-state output Single Supply PDIP-16 Signal Switches, Multiplexers, Decoders ROHSTexas InstrumentsSignal Switches, Multiplexers, Decoders
B3U-1000P
SMD,3x2.5mm-25℃~+70℃ 1.53N 1.6mm 12V 2.5mm 3mm 50mA Round Button SMD(SMT) Tab SPST Surface Mount,Vertical SMD,3x2.5mm Tactile Switches ROHSOmronTactile Switches
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
61| Qty | Value | Footprint | References |
|---|---|---|---|
| 9 | 1k | _DownloadFootprints:CF_series_Resistors_THT | R1, R10, R11, R12, R13, R14, R15, R16, R17 |
| 8 | 220 | _DownloadFootprints:CF_series_Resistors_THT | R2, R3, R4, R5, R6, R7, R8, R9 |
| 8 | LED | LED_THT:LED_D5.0mm | D1, D2, D3, D4, D5, D6, D7, D8 |
| 4 | 22pF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C5, C6, C8, C9 |
| 3 | 10k | _DownloadFootprints:CF_series_Resistors_THT | R18, R19, R20 |
| 3 | CD74HCT258E | _DownloadFootprints:2_to_1_selector | U2, U4, U6 |
| 3 | Conn_01x03_Pin | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical | J6, J7, J8 |
| 2 | 0.1uF | _DownloadFootprints:Cp_2mm_pin_spacing | C4, C7 |
| 2 | 0.1uF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C2, C3 |
| 2 | 16MHz | 8BitCPUFootprints:16MHzCrystalOscillator | Y1, Y2 |
| 2 | ATMEGA328-PU | _DownloadFootprints:DIP787W46P254L3467H508Q28 | U7, U8 |
| 2 | Conn_01x01_Pin | Connector_PinHeader_2.54mm:PinHeader_1x01_P2.54mm_Vertical | J2, J4 |
| 2 | Conn_01x02_Pin | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical | J1, J3 |
| 1 | 0.01uF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C1 |
| 1 | B3U-1000P | _DownloadFootprints:tactile_switch | S1 |
| 1 | Conn_01x05_Pin | Connector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_Vertical | J5 |
| 1 | Conn_01x10_Pin | Connector_PinHeader_2.54mm:PinHeader_1x10_P2.54mm_Vertical | J9 |
| 1 | SN74HCT245N | _DownloadFootprints:8x_tristate_transceiver | U3 |
| 1 | ~ | 8BitCPUFootprints:4x_and | U1 |
| 1 | ~ | Package_DIP:DIP-16_W7.62mm | U5 |
The 57 most common of 61 parts.
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Questions
How big is the RAM PCB?
It measures 133 × 58.5 mm and has 2 copper layers, 1.6 mm thick.
What parts does the RAM use?
61 parts, built around the ATMEGA328-PU, SN74HCT245N, CD74HCT258E and B3U-1000P. 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 RAM 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 RAM/RAM.kicad_pcb and its schematic ALU/ALU.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the RAM 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).