What mfg are GM eproms? No metric essay content

[Robert W. Hughes]

Some of the proms (TI is good about this) have the part number and
manufacturer's name etched on the substrate. Use a 50 power microscope
to look through the window and look around.

Otherwise, to read the prom I just select generic 27512 and read it in. 
If the data at $8000 is a repeat of the data at $0000 then it is a
27256.
If the data at $4000 is a repeat of the data at $0000 then it is a
27128.
If the data at $2000 is a repeat of the data at $0000 then it is a 2764.
If the data at $1000 is a repeat of the data at $0000 then it is a 2732.

Use the generic correct length chip selection at 12.5v to program. If
there are a lot of errors, then use a higher voltage.

Incidentally, plugging the prom into anything upside down will get you
one little bright white flash in the window.
-- 
Robert W. Hughes (Bob)
BackYard Engineering
Houston, Texas
rwhughe at ev1.net