14 Jun
2003
14 Jun
'03
4:15 p.m.
On Sat, 14 Jun 2003 21:13:55 +1000
"peter tremewen" <ptremewe(a)bigpond.net.au> wrote:
How much do people think is too much
restoration??? >Now obviously you aren't going to spent thousands on a system
that even
in the distant future will not even generate hundreds, and obviously >you aren't
going to rebuild and replace every part in the item, because >then it's a replica
not an antique.
Really? I have an H740 power supply sitting inside the chassis of a PDP-11/05 that wants
to argue with you. As it is, half the +5V regulator has been removed, and is going to have
to be replaced. It's not going to cost that much, but still, I fie you to call that a
"replica". The important part isn't "Oooh! Shiny old
collectible!", it's "watch me make the binkenlights do foo after I toggle
this program in on the front panel." There's a PDP-11/45 that my friend and
mentor essentially rebuilt. New power supply, grafted-on LTC, etc. Yeah, you can argue
that replacing a power subsystem is somehow devaluing the system in some way. The system
will be worthless, though, if you use a period power supply. When linear supplies fail,
they can do interesting things, like toast your logic. What is the point of having a
pristine, unmolested logic board of burnt-out chips?
A different friend of mine recently acquired a PDP-10. The KL-10 sucks down 10KW, 2 for
the CPU, 8 for the power supplies. I submit that his modifying the beast to run off of
just over 2KW, with switching power supplies, is in no way degrading the worth of the
machine. The same with his using modern memory to replace the damaged-beyond-repair memory
cabinets. A PDP-10 is a rare enough beast that anything necessary to get it running,
including hooking it up to life support, is a fair modification.
Falseness or legerdemain, however, is idiotic. Buying the shell of a PDP-11 and throwing a
PC in running simh and an interface layer in is pointless. Or repairing a PDP-8 by
reimplementing everything in FPGAs. At that point, it ceases to be the original machine
anymore.
Every DEC machine prior to the Middle VAXen came with its own print set. I hold that the
power supply is expendable. It's probably dangerous to the rest of the machine, and
should be disposed of. Earlier machines *tend* to have simpler power systems (I have a
pair of VAX 6000s should anyone want to argue the point), so it isn't completely
infeasible to build your own power supply. The more important part is the processor.
Except in extreme circumstances, I don't believe you should modify the processor. If
the print sets no longer describe the processor logic, then you've created a new
implementation of whatever the hell it was that you had. It then ceases to be the old
machine, and is some sort of weird hybrid. You're pretty much on your own then if
something goes wrong.
-Jesse