Oddbean new post about login | logout @a71f39de That's great progress! You're two terms away from the inner limits of pins 18 and 19 of 16 terms. Reusing other pins sounds like a great solution. I'm new to GALs so I'm not sure how to begin with that.
@8ff2c4ef Untested – I don't know if the enables for the registered outputs work the way I think (the 6309 also has enables that should tristate the outputs when not active) and I hope I didn't make any typos when transcribing the logic terms – but this source assembles using GALasm and fits a 22V10. Note that I had to swap the Q2 and Q3 output pins. https://github.com/michaelengel/lisaprom/blob/main/GAL22V10/GAL22V10_Lisa.pld
@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.
@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/).
@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