[sdiy] Buchla 295 10-band comb filter topology

[Pete Hartman]

On Fri, Nov 25, 2022 at 6:17 PM brianw <brianw at audiobanshee.com> wrote:

> This was in the age when nobody had yet figured out how to stop cosmic
> rays from flipping bits and causing data errors at random. It used to be
> necessary to allocate this 12.5% extra in memory just to avoid using bad
> data without warning.
>
> One of my EE professors told the story of one memory company discovering
> that the equivalent of Scotch tape backing material was enough to shield
> against interference from cosmic rays. They quietly added this to their
> DRAM chips, above the die, and watched everyone else go out of business.
> Proprietary knowledge, indeed!
>

I'm fairly certain that it must have been a little more complicated than
that, because the Sun Microsystems, struggled pretty hard with this problem
in L1 caches on their CPUs in the late 90's....  Until they put ECC on
those memories too (having had it in their DIMMs for quite a while).  I had
a rather ... boisterous customer who was hitting this problem, my boss sat
in for me in a weekly meeting when I was out of town, and the next week I
was gifted a roll of tin foil to block the cosmic rays because he had given
them IBM's 1978 (or so?) IEEE paper on cosmic rays affecting memory with
very little other explanation.

Pete
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