What kind of IC is this

Oliver Lehmann wrote: Let me guess, the logo looks a bit like the text "MMI", but in a "computer" style font? Like this: http://www.elnec.com/ic_logos/mmi.gif ? That would make it a Monolithic Memories 6306-1 fuse-link PROM. Basically a fast (for the 1980s), one-time-programmable memory device. They haven't been produced for *years*, but the cross reference at <http://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=info&page=PromRef.txt> says it's a 512x4 (512 addresses, four data bits) PROM with tristate outputs. Pinout is: +------+ A6 |1 16| Vcc A5 |2 15| A7 A4 |3 14| A8 A3 |4 13| CE/ A0 |5 12| O1 A1 |6 11| O2 A2 |7 10| O3 GND|8 9| O4 +------+ This crosses to: Signetics 82S131 Harris/Intersil 7621-5 AMD 27S13 National 74S571 Intel 3622 Your best bet out of those is probably the 82S131, which you might be able to find NOS somewhere. You'll still need a programmer, though. You can build one for the Signetics chips fairly easily (the algorithms are called "Generic I" and "Generic II"), but good luck finding a programmer for the MMI chips. I've been meaning to build a "generic" fuse-PROM programmer (I've got a couple of 82S chips in a box somewhere) but could never find the MMI programming specs. That sounds about right for an MMI part. -- Phil. classiccmp at philpem.me.uk http://www.philpem.me.uk/