RamCart 64/128

Ram Cart's background

I have been asked what that RamCart mentioned elsewhere on this site is because there is hardly any information about it in the Internet. Hence this page.

RamCart is a memory expansion module with battery backup for C64/128 that was designed and produced in Poland. At start there was only Atari version, in 1993 a C64/128 cartridge appeared. It was produced in two flavours: 64KB and 128KB.

Firmware

Provided firmware allowed to use RamCart as a memory disk, a device number 7. You could load and save files there, load directory and delete files. Note that only LOAD and SAVE worked. It wasn't possible to use BASIC command OPEN to create a file. Firmware took over control right after hardware reset and presented user with a list of stored files. By pressing a letter key it was possible to quickload a file and execute it. Hence RamCart was ideal for storing frequently used tools.

Here is a .d64 image of a disk with RamCart 128KB firmware.

rc128um.d64.gz

Hardware

As seen on pictures below, RamCart is built with 32KB SRAM chips and some glue logic. The memory is seen in a 256-byte window, placed at $DF00-FF. The upper bits of address are set by writing page number to $DE00 (and the lowest bit of $DE01 in 128KB version).

Additionaly, there is a switch that protects the memory contents from overwriting. If the switch is set to Read-Only and bit 7 of $DE01 is cleared (default), then contents of memory window are also visible in $8000-$80ff area. This allows to emulate usual cartridge takeover after hardware reset by placing boot code with magic CBM80 string in the very first page of RamCart memory.