Why do MRV11-D's crap out?

From: RMaxwell_at_atlantissi.com <(RMaxwell_at_atlantissi.com)>
Date: Thu Aug 5 17:09:00 2004

  A little clarification of Dwight's comment on EPROM life expectancy:

  The 10-year spec is for the half-life of the charge on the floating gate
of the EPROM. In other words, after 10 years, you can expect half a
programmed gate's charge to have dissipated. This, by no means, renders the
data unreadable: a smaller fraction of the charge is sufficient for the
EPROM circuitry to read a programmed cell (most algorithms do a 2x to 4x
overprogrammming once a cell reads back programmed). The
programmed/unprogrammed read threshold is also temperature sensitive, so
cooling off a warm part may allow data recovery from an EPROM that's fading
away.

  Also, bear in mind the specifications are for worst case: the charge leaks
away fastest as the device sits near its maximum rated temperature (people
have erased EPROMs by heating them over a light bulb!). The cooler the
chip, the less leakage. The relationship between temperature and leakage is
exponential, too: a few degrees make a lot of difference. If Ed's 2764As
were running hot, the gates might have lost enough charge in 15-20 years to
forget a few bits...

  This helps explain why all the EPROMs I programmed in 1985 are still
intact. They're backed up on floppy... which decays faster?

Bob

> -----Original Message-----
>
> Ed>The set of MXV11-B2 boot ROMs I have are 2764A's.
> Ed>Do these die after awhile?
> Ed>Just sitting here scratching my head.
>
Dwight> Most EPROMs are rated for 10 years. That doesn't mean that
Dwight> every one will last that long. Also, many of these types
Dwight> of systems were all made with EPROMs from the same lot.
Dwight> If there was a long term issue, they'd all fail.
Received on Thu Aug 05 2004 - 17:09:00 BST