Given that you work on space stuff, I'm sure you are correct, Alan,
but I had always heard the opposite: that SMALLER geometry made you
more radiation resistant (since smaller area meant that any one device
would receive a far smaller dose). There are two kinds of events, I
think: single-particle events and multi-particle (cumulative) effects.
A smaller geometry device will be more susceptible to the first (as
less energy is needed in the single particles to influence the
devices) but less susceptible to the cumulative effects (smaller
area=lower dose per time).

Sean

On 4/17/07, Alan B. Pearce <A.B.Pearce@rl.ac.uk> wrote:
> >IIRC the 1802 was one of the few chips that were made in SoS (Silicon
> >On Saphire) process, which made it very radiation-hard.
>
> Yeah, it was also fast and expensive. They also did CMOS RAM chips, and I
> suspect the CMOS ROM chips as well.
>
> >Space stuff often uses 'old' designs, simply because those were
> >made with larger geometries that current designs. Large
> >geometry == more radiation resistant.
>
> That is one factor, but also the costs involved in getting new parts
> certified as radiation hardened.
>
> Still using OP400 op-amps and other analogue parts from the same families.
> Many of the digital parts come under ITARS regulations when attempting to
> source US made parts, so that becomes another hassle ...
>
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