Some weeks ago I posted a question, the answer turned out to be a dodgy SDRAM controller. Any that's working well now [runs out and hugs tree].
However at the time I suspected Kingston ValueRAM which turned out to be unfounded. However there is something very strange about them. They seem to be built, not only using re-painted chips but having them two high. The modules we thought had sixteen chips (plus prom) in fact has thirty two when you look more closely. A few pins don't connect between the two decks and there seems to be a wafer in between.
Of course this does put twice the capacitive loading on the control lines which wouldn't help if we wanted to run at a decent speed. Am I being paranoid are do they do some sort of re-manufacturing using dodgy chips by perhaps fusing data lines on bad chips to end up with a module that works properly ?
Jon