Building an external CPU accelerator

From: Oliver Achten (
Date: 2003-08-20 17:23:58

Ok, let´s assume i would do an external accelerator, which is plugged into
the cartridge port.

If i undertood it correctly, it could be done the following way:
- when a write occurs, the 65816 writes to its on-board sram and a special
write buffer, which actually gets written to the C64 dram without CPU
interaction. When the buffer is full, and the CPU tries to write again, it will be
halted until the buffer is emptied.

-reads always go from its on-board sram, except the i/o locations or the

So what about the $00/01 location? It can´t be accessed by any external
device, so how could the SCPU do the trick turning on/off the char- or the system


Have a nice day!


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