The errors we're talking about here are transient. The memory location itself is still usable, the contents get changed when a cosmic ray hits. After the hit, the corrupted value is held without a problem.

Memtest checks if the memory location has a gross fault which prevents it from storing values correctly.

Doesn't seem like memtest will help.

Good point. Thanks.

I remember someone-somewhere saying that in their experience building GCC was a more thorough memory test than memtest itself...