On Apr 4, 2013, at 4:40 PM, shadoooo <shadoooo at gmail.com> wrote: You'd be looking for a KA52 CPU board. I imagine the 100A is upwards compatible with the KA53 and KA54 (faster versions of the same NVAX-based board), which may or may not be easier to find. The KA52 is DEC part 54-21797-01; it's also the same as the MicroVAX 3100/90 board. There's one on eBay here: http://www.ebay.com/itm/140880933550 $275 or best offer (good bet if you're in the US). The NVAX has pretty much everything integrated in the one chip, and the P-cache is its tiny 8K first-level cache; you'd have to replace the entire CPU, at which point you might as well just replace the motherboard. - Dave