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MOS CPU Replacer

monotech·MOS_CPU_Replacer

MOS CPU Replacer PCB layout, top view — open source board by monotech

About the MOS CPU Replacer PCB

MOS CPU Replacer is an open source PCB design by monotech, published on GitHub. It is a 4-layer board measuring 28.2 × 56 mm, with 67 components from 18 distinct parts.

Other key parts include the 6502, 595-SN74HCT245PWR, 595-SN74HCT273PWR, 771-HCT138PW118 and 771-HCT126PW118. By type, the board carries 23 jumpers, 17 diodes, 13 ICs, 7 capacitors, 5 resistors and 2 connectors.

It belongs with the retro computing designs in this gallery.

From the project

MOS CPU Replacer – replace rare/expensive/unreliable MOS CPUs

If you want one, check my store for stock: (https://monotech.fwscart.com)

The above four CPUs have the same dies I believe, with just different internal pads exposed to the DIP-40 pins. It's a standard 6502 die, with an added 8-bit bidirectional I/O port, tri-state bus buffers, and an AEC latch enable for 8501 mode.

This device uses a standard 6502 CPU, and implements the extra functions using discrete logic - no programmable parts. Standard 6502 CPUs are abundant and cheap, and produced by many manufacturers (Rockwell, UMC, Synertek, MOS, etc).

MOS CPU Replacer, from the project README
From the project README

Main components on the MOS CPU Replacer

6502595-SN74HCT245PWR595-SN74HCT273PWR771-HCT138PW118771-HCT126PW118595-74LVC1G373DCKRG4

MOS CPU Replacer bill of materials (BOM)

67 components, 18 distinct parts — part numbers from the project's BOM.

QtyPartRefs
1
6502
U1
5
595-SN74HCT245PWR
HCT245
U2, U3, U4, U5, U6
2
595-SN74HCT273PWR
HCT273
U7, U8
1
771-HCT138PW118
HCT138
U9
3
771-HCT126PW118
HCT126
U10, U11, U12
1
595-74LVC1G373DCKRG4
LVC1G373
U13
1
6510/6510T/8501
J1
1
8502
J4
1
Open for W65C02
JP1
6
A
JP2, JP8, JP14, JP15, JP19, JP22
3
AB
JP3, JP7, JP11
4
B
JP4, JP10, JP17, JP20
7
C
JP5, JP6, JP9, JP12, JP13, JP18, JP21
2
BC
JP16, JP23
17
241-1N4148WSR100001
1N4148W
D1, D2, D3, D4, D5, D6, D7, D8 +9
7
187-CL05B104KP5NNWC
100nF
C1, C2, C3, C4, C5, C6, C7
1
603-RC0805JR-07470RP
470
R1
4
603-RC0603FR-1310KL
10k
R2, R3, R4, R5

MOS CPU Replacer design files

The KiCad project lives in the monotech/MOS_CPU_Replacer repository on GitHub; these links point at the commit this page was built from.

MOS CPU Replacer: common questions

How big is the MOS CPU Replacer PCB?

The MOS CPU Replacer measures 28.2 × 56 mm, has 4 copper layers and is 1.6 mm thick.

How many components are on the MOS CPU Replacer?

67 components, from 18 distinct parts, with part numbers taken from the project's own BOM. The full bill of materials is listed on this page.

Where can I download the MOS CPU Replacer design files?

From the monotech/MOS_CPU_Replacer repository on GitHub, which has the KiCad layout, the schematic and the BOM; the links under Design files point to each one.

Can I use the MOS CPU Replacer design in my own project?

The repository has no license, so all rights stay with monotech. Use it as a reference, and ask the author before reusing the design.

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