The device [1] that's currently all over my bench has an empty 28 pin DIL socket on one of the PCBs. It's alongside a 27C256 EPROM and 43256 RAM, and has a similar pinout. In fact the pinout is the standard JEDEC one for 28 pin memory devices (with A13 on pin 26, WE on pin 27, OE on pin 22, etc) with one exception. Pin 1 is not A14, it appears to be an output, linked to an interrupt pin on the 80C85 that links to the aforementioned memory devices and this socket). Oh, and to an input port pin. Any ideas? My first thoughts were an E2PROM or simular, with a ready output on pin 1, or a RTC/memory device with an interrupt output on pin 1, but I can't find any obviuos candidates. [1] A telephone network simulator. OK, it's not a classic computer, but I will be using it to test and demonstrate classic computer modems, it's well over 10 years old, and contains 6 microprocessors... -tony -------------------------------------------------------------------- myhosting.com - Premium Microsoft? Windows? and Linux web and application hosting - http://link.myhosting.com/myhosting