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2 layers102.5 × 30 mmCpu, the printed circuit board in 3D

Cpu

atarola/compy6502

Code for my 6502 build

Open in PCBKitView on GitHub.kicad_pcb
Size
102.5 × 30 mm
Copper layers
2
Thickness
1.6 mm
Parts
10
Nets
49
Pads
102
Tracks, vias
172, 19
Pours
2
Routed
Yes
KiCad
KiCad 10.0 (file 20260206)
Created
24 Nov 2019
Updated
19 Jul 2026

Overview

Cpu is an open-source printed circuit board by atarola, from the atarola/compy6502 repository on GitHub. It is a 2-layer board of 102.5 × 30 mm with 10 parts on 49 nets, routed with 172 tracks and 19 vias.

Its parts include 5 resistors, 2 capacitors, 2 connectors and 1 IC. It belongs with the retro computing and games boards of this library.

README

README.md

compy6502

compy6502 is an early-stage 6502 homebrew computer project. The long-term goal is to build enough hardware and firmware to run Tetris on the machine.

The design follows the spirit of Ben Eater-style breadboard/modular 6502 systems for simplicity and debuggability, but uses a different memory map based on the MMU/address-decoder architecture in docs/mmu.png.

The repo currently includes KiCad hardware designs, early ROM bring-up firmware, build/write scripts, emulator test scaffolding, and architecture reference images in docs/.

Memory Map

The intended memory map is:

text
$0000-$BFFF  RAM
$C000-$C0FF  I/O page
$C100-$FFFF  ROM

The I/O page is split into four 64-byte device slots:

text
$C000-$C03F  IO0B
$C040-$C07F  IO1B
$C080-$C0BF  IO2B
$C0C0-$C0FF  IO3B

The linker script currently uses $8000-$FFFF as the 32 KB EEPROM image range so CPU addresses map directly to the correct physical offsets on the chip.

ROM Layout

The intended ROM organization is:

text
$C100-$C1FF  public jump table
$C200-$DFFF  kernel routines and drivers
$E000-$EFFF  enhanced monitor
$F500-$FFF9  Wozmon fallback monitor
$FFFA-$FFFF  CPU vectors

Credits

  • docs/mmu.png: Mike McLaren, K8LH.
  • docs/Beater 02b.png: Mike McLaren, K8LH.

Parts

10
QtyValueFootprintReferences
53.3kResistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_HorizontalR1, R2, R3, R4, R5
10.1uCapacitor_THT:C_Disc_D3.0mm_W1.6mm_P2.50mmC1
110uCapacitor_THT:CP_Radial_D5.0mm_P2.50mmC3
1Board ConnectorConnector_PinHeader_2.54mm:PinHeader_1x40_P2.54mm_HorizontalJ1
1Conn_02x04_Counter_ClockwiseConnector_PinHeader_2.54mm:PinHeader_2x04_P2.54mm_HorizontalJ8
1W65C02SxPPackage_DIP:DIP-40_W15.24mm_SocketU1

Questions

How big is the Cpu PCB?

It measures 102.5 × 30 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Cpu use?

10 parts. 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 Cpu KiCad files?

From the atarola/compy6502 repository on GitHub, at the commit this page was made from: the board is kicad/cpu/cpu.kicad_pcb and its schematic kicad/ACIA/ACIA.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Cpu design in my own project?

Its repository states no licence, so its author keeps all rights: ask atarola before reusing the design.

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