[cctalk] Re: Computer Museum uses GreaseWeazle to help exonerate Maryland Man

That reminds me of a PDP-11 diagnostic -- not usually run -- called the "core heating test". The way I remember the description is that it would do rapid memory accesses in a set of addresses that are physically close in the core memory (obviously this is model-dependent). The idea was to find marginal memories. One reason for not running that test is that it was very slow. From the same era I recall that our IBM 1620 mod 2 had a heating system for the memory cabinet, and that after power up you had to wait 10 minutes or so for the memory to be warmed up to its normal operating temperature. I don't think I ever saw an explanation why this was done. It's puzzling that temperature would matter. Obviously, when you hit the Curie temperature the data goes away, but for typical magnetic materials that is in the hundreds of degrees. Does the hysteresis curve shift enough at moderate temperatures (a bit over room temperature) to matter? paul