David Comley <david_comley at yahoo.com> wrote: Sounds unlikely that they indicate ECC errors if the are on most of the time, even if dim. Access seems much more likely. It is the memory controller. The board itself is a pretty stupid array of memory cells. Even ECC isn't handled on the board, if I remember right, but is handled by the controller. The board just gives 39 data bits for every 32-bit word. And at startup, every memory board is accessed in parallell by the controller to initialize the ECC bits. So they should all be glowing brightly at startup if it is an access indicator. But in that case, I would expect them all to then turn off as no memory access will be going on after that, until the machine boots. That makes sense. If you remove any board in the middle, you get a weird hole in the memory map, which is illegal. The board at the left end is the last board, so removing that one isn't a problem. You don't create a hole then, you just reduce the amount of memory you have. Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol