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by razzio
1576 days ago
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Ah yes that brings back memories. I knew that book inside-out. I made the ROM writable by soldering a CMOS ram chip across the ROM (was it 16KB?) and any write to the ROM would end up in the RAM. A switch selected either the ROM or RAM to read from. On startup simply copy the ROM to the RAM and flip the switch. After this operation, using 'The Spectrum ROM disassembly' book the world was your oyster. I modified the ROM routines for reading/writing those little tape drives and bypass copy protection, for experimental purposes of course :) |
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