2 Apr
1997
2 Apr
'97
12:53 p.m.
[EPROMs]
I'm not an electrical engineer, but as I
understand it, it's not an
actual problem with the hardware of the machine itself. It's just that
the magnetic alignment in the EPROM (erasable programmable read only
Actually, it's an electrostatic charge that leaks away. The effect is much
the same, though - the chip can be reprogrammed, and works fine. It just
forgets the data that should be in it.
But chips (_all_ chips) can and do fail. So I'd recomend backing up ROMs,
PROMs (the fusible-link type used for address decoders, state machines,
etc), PALs, etc. Everything.
memory) disintigrates. However if you have a backup
of the chip, it can
be re-programed using an EPROM burner.
I know that for Atari 2600 cartridges, only prototype and low-quality 3rd
party cartridges were made with EPROMs in them. I'd be surprised if any
Yes, but ROMs can fail as well. You should still keep backups.
machines actually use EPROMs to store the ROM kernels,
but perhaps they
do. If so, a list of affected machines should be made. Perhaps I should
Classic PERQs have an EPROM on the I/O board for the Z80 code. PERQ 3a's
have the bootstrap in EPROM. I've got DEC-compatable boards with EPROMs on
them. I'm sure a lot of other machine have EPROMs in them - particularly
the machines made in smaller quantities - which are therefore rarer, and
more important to preserve.
Remember that an EPROM need not be in a ceramic package with a quartz
window. OTP (One Time Programmable) EPROMs are in a normal plastic
package. They can't be erased by UV light (there's no way for it to reach
the actual chip), but they program just like EPROMs, and they suffer from
bit-rot just the same. If in doubt, back it up.
I've always wondered about the use of electrolytic
capacitors in
computers. I believe that these buggers go bad after a while and need to
be replaced. Is this true?
Well, it's not a real problem. I've had exactly one big electrolytic fail
in _all_ my computers (and I have machines over 25 years old). That one
was in a PDP11/44, and was damaged when the PSU overheated (amazingly, it
was the only damage!).
But capacitors are standard parts. Unless you insist on only using the
original manufacturers components, it's not hard to find replacements for
them. I don't worry about that at all.
I've also always been concered about floppy disks going bad. Do they
have a definately lifespan? If so, it might be hard to find new 5.25", 8"
or 3.25" (a la Amstrad) disks on which to copy ailing files.
Yes, disks do go bad after a time, alas. The only compensation is that the
older disks (particularly 8") seem to last a lot longer than the modern
3.5" ones.
chris starling
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill