Imagen memory woes
laser-lovers@uw-beaver
Alas, testing every one out of every 1K bytes (or other large chunk)
fails miserably as a memory diagnostic. I suspect that this is
how Imagen's software counts up available memory in the first place;
and I know for a fact that Unix counts up Vax memory using this
method.
Memory diagnostics are subtle things. There are `walking 1s',
`walking 0s', `refresh delay', `address line short', `data line
short', and other standard tests, yet these do not even begin to
cover some of the interesting faults that can hide in modern dynamic
RAMs. A good test program will try all of these and will also run
a pseudo-random number generator. A truly thorough test takes on
the order of eight hours per 64K!
My information on dynamic RAM problems is dated, so my figures
may well be off; but suffice it to say that a power-up self-test
cannot perform a complete check. Perhaps what Imagen should
provide is parity error detection and/or diagnostic floppies.
Chris