In message <s36474ea.012@microbits.com.au>, Peter Wintulich writes:
>? Is it likely that some UV eraser bulbs emit different frequencies and that
> could penetrate the
>die they use more easly & therefor erase the eprom cells more easly.

        It is possible, but what is more likely is that the higher-powered
lamps just get the UV through by brute force.

        I have been following this thread and it seems like the idea of
requiring much more energy to zap the code-protect fuse than it does to
erase any of the other bits makes the most sense since accidents happen
and they always will.  Putting more die over the CP bits to make the covering
totally opaque is sort of like throwing the baby out with the bath water.

        If there is a chance that somebody might figure out the physical
location of the CP cells, another fix might be to put a frosted window
over the die so that any attempt to focus light on one particular spot would
cause it to defuse enough to zap adjacent bits.

Martin McCormick