Correct me if I'm wrong, but the 1227747 uses a 2732 which is a 4Kx8 (32Kb) chip, the 28C64 is an 8Kx8 (64 Kb) chip, the SF512 is a 64 KB, being a 512Kb chip...I think. The big difference is the B vs the b, bits vs Bytes.
Today, after spending a few hours figuring out how to use my 30 year old Needhams EMP-20 programmer, I successfully programmed the AT28C64B with buffer offsets 1000-1FFF, which should be the last 4K of the 8Kx8 space, the first 4K being 0000, 0FFF...I think. It's been years since I have done this stuff. I confirmed data in the chip matches the data in the buffer, but just offset to the last 4K of the 28C64. I built the 28P ZIF mod socket and soldered it onto the 747 board today, I won't know for a while if it works, but it should.
Thanks for the help.
Cheers
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