> > Maintaining original labels is going to be hard to do,
> > as the EPROMs age. I've already had to refresh some
> > EPROMs from equipment as recent as 1982.
>
> Unless your programmer insists on doing a blank-check before programming,
> you can often refresh EPROMs without erasing them. And thus the label can
> stay in place. You can often refresh OTP devices in the same way.
>
> After all, bit-rot is caused by the charge on the floating gate leaking
> away. Charge that was put there when the device was programmed. So it can
> be put back by reprogramming _without erasing first_.
I've actually had an EPROM that would not take the new
programming until I erased it, and the programmer did
not require the device to be blank first.
> Well, as I said I wouldn't mention the things I'd raid for chips to avoid
> flames, but IMHO a no-name PC card is somewhat less significant than a
> DEC CD-ROM drive. However, this is most certainly a matter of opinion.
That's true, if they were old unique drives. I don't think
the new RRDxx CDROM drives are unique.
> As you said, in some cases the only place to get parts from is to raid
> them from an old machine. But some machines are a lot more common than
> others. Would you rather strip RAM from a no-name PC motherboard or from
> a PDP11?
I'd rather strip anything from a no-name PC motherboard than
a PDP-11.
> > > You can bet there's a collector who is trying to get one of every model
> > > of DEC storage device or something who will want an RRD40.
> >
> > That may be the case, but where do we draw the line?
> > Of course one man's trash is another man's treasure,
> > but will everything be worth keeping? And how do we
> > justify what we restore and cannibalized? For instance,
>
> My justification, such as it is, is that I don't cannibalise anything
> unless there is _no_ alternative (i.e. the parts simply aren't available
> any other way, and there's no reasonable workaround) and that if I do
> have to cannibalise parts, I think very carefully what I am stripping,
> and how rare it is. In some cases it's better to leave the device I need
> parts for unrepaired for the moment rather than stripping them from an
> even rarer system. Of course stuff that's already been partially
> cannibalised by someone else is often only useful as a source of parts.
That's a good way to look at it.
> > the MVII I am converting to a PDP-11. I've had good
> > feedback on the conversion, but nobody has said to me
> > that I should keep the MVII intact and sell it complete
> > and buy a complete PDP-11 or all the parts. For the
>
> That is rather different. The only way to get the Q-bus backplane, case,
> PSU, etc (without a _lot_ of work trying to make them all from scratch)
> is to start from another DEC machine. Presumably, also, you pulled out
> the CPU board and memory boards of the microVAX and kept them intact. In
> which case they could be useful as spares for somebody trying to repair a
> microVAX with a CPU board fault, for example. That's rather different
> IMHO from removing common, easy-to-get chips from a board.
Well, yes, I am keeping the boards intact.
> > RRD40 drives, I offered them, with the controller board
> > thrown in, but the drives in no way require the controller
> > board to operate. The drives were normally sold to be
> > used with the RRD50 controller; the SCSI adapter boards
> > were just a kludge to get the drives to work with SCSI
> > controllers. I took them out of the Infoserver 100 and
>
> Sure. And since the SCSI interface wasn't normally used with these
> drives, surely it means that the SCSI interface is something that's
> relatively rare and worth keeping intact.
I didn't look at it that way.
> > replaced them with compatible SCSI CDROM drives so I
> > could have a functioning system. Should I have kept the
> > Infoserver 100 pure instead? That would have meant the
>
> I would have done. What's wrong with the original CD-ROM drives. I'd have
> been inclined to repair said drives (IIRC, they're actually an LMS-based
> design, and parts may well be available...)
Oops, LMS. I was thinking LSI. Anyway, the problem with the
original CDROM drives is they require a special, hard-to-find
and hard-to-use caddy. The system was unusable with the RRD40
drives. The caddies used in the RRD40 drives were hard to load.
I've dropped a couple of CDs trying to load the caddies.
--
Eric Dittman
dittman_at_dittman.net
Received on Tue Apr 24 2001 - 16:35:23 BST