Re: Mouse card --- Can EPROM go Bad?

[Patrick Schaefer <pa.schaefer@fz-juelich.de>]

Rubywand wrote:

> > Can the mouse card IIe eprom go bad?
> 
>      If it's an EPROM, it can go bad. Mainly, it can 'forget' and need
> to be re-programmed.

Usually EPROMs lose their information after 10..12 years. In the
beginning you can read out the data with a (rather slow) eprom burner
and only the fast CPU access fails, some time later all information is
lost. The chip itself is not damaged, only erased!
The retention time gets shorter if the chip is exposed to light or
X-rays. Therefore the glass window should be covered with a metal-coated
label (e.g. a disk write-protect tab)

It is a good idea to refresh the EPROMs every 8..10 years. Read out the
data and write it back into the chip. You don't need to erase it before
programming.

This may also apply to ROM chips. Most of the 'mask programmed ROMs',
e.g. 2316, are actually EPROMs without a glass window.


Patrick