I really don't know what I was thinking...dougeff wrote:16 banks = 0x10.
That means you can access the ROM either by bank numbers 0 - 0x0f or 0x80 - 0x8f.
There isn't a bank 0x90, if your ROM size is 512k.
EDIT: but this still does not explains how I managed to use banks 0x88 and 0x89 when ROM size was 256kb