I purchased a Series 22.... and now that I've ruined 6 Harris 7641 equivalent PROMs (minimum value about $15)... I've determined what the symptoms are I am seeing. This is a 512 byte PROM. I'm thinking A6 line to the PROM during read is either high or floating, as if you break the 512 byte range into 8 blocks of 64 bytes you should have ABCDEFGH When I read a good source rom in, I use edit and compare it against a known good hex dump, and I'm seeing BBDDFFHH with blocks A, C, E, and G missing. This would seem to idnicate that the A6 line is high during read. Unfortunately my MOD-EMUP which should handle these PROMs 49 times out of 50 (or so it seems) will read any 7641 or compatible as all FFs (which it probably ins't reading anything... and the FFs were part of the EMUP's software clear). I think I read you can read these as a 2732 and the 512 bytes ends up repeated I think in specific positions in the read.... I have to google that again to see if during the writes, the A,C,E,and G blocks are all 0 still like on a blank PROM. I'm going to strip it down to look at the boards... and check first at the socket. If that line is floating will I get this behavior, or only if it is driven high ? Thanks, -- Curt _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com https://pairlist7.pair.net/mailman/listinfo/techtoolslist FTP site is: ftp://ttl.arcadetech.org/TTL/Test_Equipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/