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paulrickards | 1 years ago (raw) | root | parent | reply | flag 
 @a71f39de Terrific! Good news, both enables on the Lisa are grounded and never change. I have some GAL22V10B on order. I’ll also start working on an adapter board.
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00e23f64 | 1 years ago (raw) | root | parent | reply | flag 
 @8ff2c4ef Ha, I also just checked that the enables are grounded 🙂. The schematics seem to indicate that the MSB output bit 7 only gives a signal "SN" (https://github.com/warmech/lisa-hardware/blob/main/CPU%20Card/Schematics/Video.pdf), so I assume this is only used to generate the "magical" Lisa serial number – there are three different versions of the PROM on bitsavers (SN_*.BIN at http://bitsavers.informatik.uni-stuttgart.de/bits/Apple/Lisa/firmware/).
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paulrickards | 1 years ago (raw) | root | parent | reply | flag 
 @a71f39de I suppose that would explain why bit 7 is so hard to reduce because it has more randomness. Would be great to understand the serial number format to assign proper new serial numbers to all of the #AppleLisaClone being built. 

Good news is the PROM on the I/O board for the floppy should be the same for all of the clones. 

http://www.bitsavers.org/bits/Apple/Lisa/firmware/341-8003-A_f95908934da6460a67abc26c2f0d1553.BIN