You just stirred my faulty memory. It wasn't cosmic rays, it was alpha
particles coming off the ceramic substrate. That's why a coating of (I
think) RTV was effective.
Chuck Norcutt
Tim Hughes wrote:
> I don't think it was "cosmic ray" protection, I think it might have been
> alpha particles from the
> universally used special type of epoxy encapsulation, and so could be
> screened by a suitable thin
> coating. Unfortunately it is a very long time since I read that, and my
> "analog memory" is hazy
> having been hit by too many particles in the meantime. I was just verfiying
> Chuck's memory there
> was some issue related to the smaller and smaller amounts of stored charge. I
> believe the
> Norden-Fowler tunneling mechanism used for programming of flash memory,
> damages the extremely thin
> oxides used because of the extremely high voltage gradients that must be
> used. That is why there
> is a limiting cycle life wear out mechanism.
> Tim Hughes
>
> --- keith_w <keith_w@xxxxxxxxxxxxxx> wrote:
>
>
>>Tim Hughes wrote:
>>
>>>I seem to remember reading the normal memory chips suffer from ionizing
>>>radiation hits,
>>
>>(because
>>
>>>the number of electrons stored has got to be so small), but they now
>>>encapsulate/cover the
>>
>>chip
>>
>>>surface to minimise the effect.
>>>
>>>tim Hughes
>>
>>What are they going to cover the chip with that will stop cosmic or gamma
>>rays
>>from zinging right on thru?
>>
>>keith whaley
>>
>>
>>>>that too. But I do not know if those bits will eventually fade off into
>>>>the void sitting in the closet or if they're subject to flipping from
>>>>cosmic rays.
>>>>
>>>>I do know that cosmic rays were a worry to at least one of IBM's memory
>>>>engineers when chip density hit 64K bits about 30 years ago. But that
>>>>problem was obviouly solved or else maybe didn't exist in the first place.
>>>>
>>>>Chuck Norcutt
>>
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