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I just stumbled on an Apple II "clone" that uses a GI 9128B-1180 chip for the ROM.

The curious thing about it is the wire soldered on a leg. So, my hypothesis is that they didn't have the usual part available and used this instead. I want to dump the ROM to maybe modify it and burn another chip that is readily available to use in its place. I think I could use a 27C128 for this small project, but I want to be sure about the compatibility of it before attempting anything on this ancient hack (the wire scared me a little).

TK2000 ROM Chip

Greenonline
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Z8Michael
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    Think about what this site is; it's a question and answer site. So, you need to ask a question. – Andy aka Dec 15 '22 at 20:13
  • Where does the (other end of the) wire go to? This end seems to go to pin 26 (A13). – Greenonline Dec 15 '22 at 20:18
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    The _workmanship_ on that wire is certainly scary. If that was a factory mod, it wasn't the best factory. It looks like the solder blob shorts to pins on the chip right above it -- if the thing works that may be intentional, and you should take it into account. – TimWescott Dec 15 '22 at 20:35
  • http://www.txbobsc.com/scsc/scdocumentor/ – Antonio51 Dec 16 '22 at 09:21

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According to the 1982 GI Microelectronics Data Catalog page 41, the RO9128B is a 16,384 x 8 bit mask ROM. Pin 26 is A13, the same as on a standard 27128 EPROM. The other pins are also the same except for pin 27, which is /PGM on the 27128 but CS1 on the 9128. However this is still compatible because /PGM is held high on the 27128 during normal operation.

Your clone board may originally have been designed to take a pair of smaller ROMs which had separate chip selects enabled by A13 being low or high. You should be able to 'dump' it using the same connections and signals as a 27128.

Bruce Abbott
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