C128-mmu-256k exp
About the C128-mmu-256k exp PCB
C128-mmu-256k exp is an open source PCB design by ytmytm, published on GitHub under the MIT license. It is a 2-layer board measuring 48.3 × 90.2 mm, with 12 components from 10 distinct parts.
Other key parts include the 8722_MMU, 74LS138, 74LS00, 4066 and 74LS32. By type, the board carries 7 ICs, 3 connectors and 2 resistors.
It belongs with the retro computing designs in this gallery.
From the project
C128 MMU 256K RAM expansion
This work is based on a project developed by Marko Mäkelä and Pekka Pessi that described expanding Commodore 128 memory to 256 or 512/1024 kilobytes of RAM.
Two KiCad projects capture schematic and PCB for 256KB expansion only.
This is a daughterboard meant to be plugged into U7 socket to raise the original MOS 8722 MMU chip and add a second one to generate /CAS signals for RAM banks 2 and 3. The challenge was to make it narrow enough to fit into C128DCR - there is not much space near MMU socket between power connector, power supply and SID.
Main components on the C128-mmu-256k exp
C128-mmu-256k exp bill of materials (BOM)
12 components, 10 distinct parts.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 2 | 8722_MMU | DIP-48_W15.24mm_Socket | IC5, U7 |
| 1 | 74LS138 | DIP-16_W7.62mm_Socket | IC6 |
| 1 | 74LS00 | DIP-14_W7.62mm_Socket | IC7 |
| 1 | 4066 | DIP-14_W7.62mm_Socket | IC8 |
| 1 | 74LS32 | DIP-14_W7.62mm_Socket | IC9 |
| 1 | 8722_MMU | DIP-48_W15.24mm | U7_SOCKET1 |
| 1 | U9-CHIP | PinHeader_1x02_P2.54mm_Vertical | J1 |
| 1 | U9-SOCKET | PinHeader_1x02_P2.54mm_Vertical | J2 |
| 1 | TO NEW RAM CHIPS | PinHeader_1x02_P2.54mm_Vertical | J3 |
| 2 | 68 | R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | R3, R4 |
C128-mmu-256k exp design files
The KiCad project lives in the ytmytm/c128-mmu-256k-exp repository on GitHub; these links point at the commit this page was built from.
C128-mmu-256k exp: common questions
How big is the C128-mmu-256k exp PCB?
The C128-mmu-256k exp measures 48.3 × 90.2 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the C128-mmu-256k exp?
12 components, from 10 distinct parts. The full bill of materials is listed on this page.
Where can I download the C128-mmu-256k exp design files?
From the ytmytm/c128-mmu-256k-exp repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.
Can I use the C128-mmu-256k exp design in my own project?
Yes, under the terms of its MIT license, which ytmytm chose for the repository.
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