Mike asks: It isn't unusual to find that many years after manufacture, that a particular batch of DRAM chips aren't reliable anymore. DEC and other memory board makers used to keep internal lists of known good batches and known bad batches of chips, and even kept track of what brand/batch are shipped with each memory board for long-term reliability tracking. But it seems more likely that something marginal in the timing of the motherboards or the power supply or something else is causing your observed flakiness. I don't really understand what you mean about the Apple II's "wouldn't boot", though. They do not do an extensive (or any!) power-on memory test but maybe loading DOS 3.3 is hitting RAM hard enough at power on that it's turning somethng else up. As others have noted, just going into BASIC at power-up doesn't hit memory too hard, and the quickie tests of going into hi-res graphics and looking for flakiness on the screen is useful if not definitive. Tim.