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2 layers190.5 × 105 mmBackplane, the printed circuit board in 3D

Backplane

atarola/compy6502

Code for my 6502 build

Open in PCBKitView on GitHub.kicad_pcb
Size
190.5 × 105 mm
Copper layers
2
Thickness
1.6 mm
Parts
53
Nets
58
Pads
372
Tracks, vias
340, 21
Pours
2
Routed
Yes
KiCad
KiCad 10.0 (file 20260206)
Created
24 Nov 2019
Updated
19 Jul 2026

Overview

Backplane is an open-source printed circuit board by atarola, from the atarola/compy6502 repository on GitHub. It is a 2-layer board of 190.5 × 105 mm with 53 parts on 58 nets, routed with 340 tracks and 21 vias.

Its parts include 16 resistors, 16 diodes, 8 capacitors, 8 connectors and 1 switch. 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

53
QtyValueFootprintReferences
1610kResistor_SMD:R_0603_1608MetricR1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16
16~LED_SMD:LED_0603_1608MetricD1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, D14, D15, D16
70.1uCapacitor_THT:C_Disc_D3.8mm_W2.6mm_P2.50mmC2, C3, C4, C5, C6, C7, C8
7Board ConnectorConnector_PinHeader_2.54mm:PinHeader_1x40_P2.54mm_VerticalJ1, J2, J3, J4, J5, J6, J7
4MountingHole_PadMountingHole:MountingHole_2.2mm_M2_PadH1, H2, H3, H4
1100uCapacitor_THT:CP_Radial_D8.0mm_P5.00mmC1
1SW_SPDTButton_Switch_THT:SW_E-Switch_EG1271_SPDTSW1
1Screw_Terminal_01x02TerminalBlock_Phoenix:TerminalBlock_Phoenix_MKDS-1,5-2-5.08_1x02_P5.08mm_HorizontalJ9

Questions

How big is the Backplane PCB?

It measures 190.5 × 105 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Backplane use?

53 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 Backplane KiCad files?

From the atarola/compy6502 repository on GitHub, at the commit this page was made from: the board is kicad/backplane/backplane.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 Backplane 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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