Has anybody ever tried sticking a 61512 extracted from the cache array on an old '486 board onto a daughterboard with the CPU in one of these boxes? I've done that with quite a number of different Z80's and had pretty good luck. What makes it work really well, but limits the application to those cases in which the memory map is monolithic, is modifying the system ROM to include a routine to copy the ROM into the SRAM on hard reset, and then disabling itself by means of a flipflop that is set when the top address is written. I can provide details, but, believe me, it has saved me lots of hassle with memory interfaces, since DRAMs often go wierd and require considerable effort to fix, since they're often stupidly designed. SRAMs as you are trying to replace are generally less likely to go bonkers, but if you want to expand the memory, the method I've suggested works rather well and maxes out the memory map. It also allows you to increase the CPU speed considerably. Dick ----- Original Message ----- From: "Pete Turnbull" <pete(a)dunnington.u-net.com> To: <classiccmp(a)classiccmp.org> Sent: Sunday, March 24, 2002 7:15 PM Subject: Re: ZX81 and 6116