30 May
2000
30 May
'00
12:28 p.m.
You're right, you can DESTROY data recorded on an EPROM. You have to set
about to do that, however, and I know few archives where that's likely to be
tolerated.
If you put floppy diskettes on the shelf and wait 20 years, you'll see
what's left of your archive.
Dick
----- Original Message -----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, May 30, 2000 5:52 PM
Subject: Re: Defining Disk Image Dump Standard
so
if
You don't get it, do you?
No, _You_ don't get it.
We're not talking about making an archive _on_ floppy disks. We're
talking about defining a format for a file to be used to store the
contents of floppy disks.
This file can be stored on just about anything. Magnetic disks, magnetic
tape, multiple reels of paper tape, EPROMs, Bubble memory, you name it.
The idea is that floppy disks (that's real floppy disks) from classic
computers (which, like it or not are what this list is about :-)) can
then be archived on something a little easier to preserve and a little
easier to transfer around the world than the physical disks.
environmental conditions. OTP EPROMS are pretty
stabile, however, and
they're VERY small.
Rubbish!.
I am _not_ going to trust my data to charges stored on the floating gates
of some chip. No way. Even the manufacturers quote data lifetimes of a
few 10s of years at most. That is not archival storage. Nor are EPROMs
particularly robust -- they can be damaged by static, head, misapplied
voltages, etc.
I back up EPROMs to other media, not the reverse...
>
> If you're serious about creating an archive. It needs to be permanent,
it's
essentially requisite that the media be write-once. I'd say you're
Actually, OTP EPROMs are not write-once. You can write them as many times
as you like. The only thing is you can only change a '1' into a '0', and
never the reverse. So you could 'erase' the archive (simply fill the
EPROM with 0s). Or corrupt it (flip a few odd 1's to 0's).
FWIW, the Psion Organiser (an early UK-made PDA) had plug-in EPROM
cartridges. These were used as file storage devices. A file could be
'deleted' by setting a bit in its header to 0, whereupon the system would
no longer find the file, but obviously it would still take up space on
the EPROM. The Datapak (EPROM module) could be 'reformatted' in a special
formatter, which was nothing more than a UV-eraser.
> better off with an OTP EPROM. Hardware to create them is dirt-simple to
> create, eraseable/rewritable equivalents are readily available, and even > the OTP's (very inexpensive, by the way)
become scarce, there will still
be
> rewritables available which can be write
protected by removing the VPP
or
> program pin. Use those and you'll have a
real archive. What's more,
there
Incidentally, a lot of EPROMs don't like having Vpp floating, they want
it tied to Vcc (normally). Ditto for PGM/
-tony