Just an update on the 8751 programming problem I had.

Two readers were kind enough to take up my offer and test out some AMD 8751H's for me. Both were successful, one using a PB-10, the other an EMP-20. That seems to throw the OTP lock bit theory re: windowed 8751's out the window...

I had come up with my own adapter for the PB-10 programmer because Needham's stopped selling them a long time ago.

I followed the 8051 datasheet programming notes carefully, and my adapter has the Xtal oscillator (the 8751 needs a 4-6 Mhz clock during programming). The only thing that still puzzles me is why an Intel 8752BH programs fine, and AMD 8751s don't. I can't figure out the difference, everything in the datasheets indicates the 8751H is a just a subset of the 8752BH (some of the programming levels are don't cares on the 8751H, and there's only one lock bit). I don't know what's missing from my home-brew adapter. Oh well, enough time wasted on this problem, I'll be using in-circuit programming on Atmel 89C52s in the future.