6502 RAM/ROM Expansion Prototype page

This expansion was intended to give your PET or CBM computer 32kB RAM and 128kB FlashROM with many configuration options on a small board that mounts in the 6502 socket. The RAM is used as system RAM and will replace all the onboard RAM of the computer. The FlashROM offers four banks of system and option ROMs that can be selected independantly. It's especially useful when used in the original PET machines that have only 4 or 8kB of memory, an outdated version of BASIC and no option ROM sockets. With this board, you can have 32kB RAM, all versions of BASIC (1.0, 2.0 and even 4.0!) and option ROMs.

Thanks to the use of a programmable logic chip the expansion will work in many other 6502 based systems as well. See the main page for more information.

The prototype, inside an original PET 2001 finally, a fully expanded PET!

In the VIC-20 some sockets are needed to get above the heatsink
Installed in the 1541 with DolphinDOS (which can be replaced now)

Here are some pictures that show the device in different states of development:
The first prototype

The solder side of the second prototype
second prototype, with soldered in components
second prototype, with socketed components
Final version, with optional SMD-SRAM and precision sockets
Final version, bottom side, with dual SIL precision socket adaptor


If you have questions about this project,  you can mail me: please visit my contact page.