OK...I have an 88 firebird I took the ecm out of...it 'had' a 305 tpi in it(VIN 'F'), which someone replaced. The ECM number is 16082321, which I cannot find any info on. Is this a '165 computer with a different part number? Now here's the fun part. It has two harness connectors, a Memcal/prom carrier which is left to right in the ecm, but the Prom is a 27C256!(with a factory cal label on it), not a 27c128 as described in all of the ecm breakdowns. Anyone got any clues? Oh, cal code is AKFN. Any help is appreciated.

 

http://holman.cs.uml.edu/~sdurphey/b...b.cgi?BCC=akfn

Don't know why it would have a 27c256 instead of a 27128 though.

 

Thanks that helps alot! I'm not sure why it has a 27c256 in it, but i do know that as long as the pins are wired correctly, you can use that device, programming the right memory space. Maybe by that time, 27c256's were easier for the factory to obtain. who knows. Anyway, that site is extremely helpful.

 

A 27C256 can be used in place of a 27C128, they just put the 16K Bin (the programming) on the top half of the 32K space available on the 27C256.

The cost for a 27C128 is pretty the same as a 27C256. Given the volumes GM purchase these eproms in, they probably got a better price break on buying exclusively 27C256s. But this is all second guessing, since only GM knows for sure.

Bottom line though, you can use 27C256s in place of the 27C128s - but AT29C256 Flash Proms are the best to use for either.