On Dec 9, 11:23 am, mdj <mdj....@gmail.com> wrote: > I didn't do the math, but I would have thought 150ns was marginal at > 3.6Mhz considering the Apple II refresh scheme. Unless the TW IIe uses a different refresh scheme? It could use the RDY line into the processor to steal a cycle often enough to keep the DRAM chips refreshed. I will have to hang a logic state analyser off my card and see.