What were they thinking?

[Dan Plaskett]

Lightbulbs have started going off lately.  Perhaps I'm just stupid, but did
anyone else know that GM was using 27C256 chips in the 86-89 TPIs.
Everything I had read said that they were supposed to be 27C128s.  I set my
eprom programmer to read 27C128s, made sure the checksums were the same all
the way through, documented each step as I'm going along, then bam I hit a
brick wall when trying to program the chip after erasing it.  Error, error,
error.  No identification on the chip of course.  By some stroke of luck
however one of the chips did respond when asked for self-identification.
Guess what, it's a 27C256.  Reset the configuration to burn that chip, no
more problem.  Since the bin files I created were all 16K I am assuming that
the back half of the chip was blank.  I did get a different sumcheck on one
of them using the configuration for 27C256.  But the bin file that I created
and the readouts from TunerCat were identical, so I am assuming that it's
OK.  There I go assuming again.  Just thought I'd pass that along for any
novices like me out there.

Dan Plaskett

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