Thanks Pete for your fast answer. Yes it is a BASIC 4 Machine with these 4116-4 RAMs. You wrote the correct substitute for the ROM chips are Texas Instruments TMS2532 or equivalent. Is this right for all the chips I will list below? I hope the TMS2532 are easy to purchase here in Austria. Looking through my little library I found the datasheet (at least a good start) but I couldn't find a refence for substitutes - do there exist any? Are the TMS2532 fully Pin-compatible with the MOS ones? And my last question: Do I need anything special to write these chips? I'd put together a little circuit to hook on my Pc's Parallel-Port (this would be the easiest way for me). I'm already googling for information, but would be very glad of some links to schematics and software. Best regards, Wolfgang ==================================================== Ing. Wolfgang Eichberger cell.: +43-664-240-65-92 http://www.eichberger.org email: wolfgang(a)eichberger.org ---------------------------------------------------- Gruentalerstr. 24 - 4020 Linz ? AUSTRIA ====================================================