Hi Rod,
On Monday 04 June 2007 23:37, Rod Smallwood wrote:
Hi
Well done that guy!!
What you have done is both the spirit and the essence of classic
computing.
You are to be congratulated on both effort and persistence.
Thanks. Lots of work - but mostly fun :-)
"A shining light to lead others into the darkness
of old computer
restoration"
Blush... I do my best - I'm on both the PDP-1 and IBM 1620 Restoration Teams
at the Computer History Museum...
I was at DEC (UK) in the 70's and Modcomp would
pop up as competition
from time to time.
Hasn't that front panel got DEC overtones?
A bit - but so do most Minicomputers in the mid-70's ;-)
It's different from most DEC minicomputers in that you can access not only the
systems 15 general purpose registers, PC, etc. but also about 40 other
internal registers and status conditions. You can also modify most of them
from the front panel! (BTW: It has a
"protect" switch to keep the wrong folks
from doing nasty things when in operation - and also internal protection
mechanisms, etc.)
It's different enough that when I move from my 8/E, 11/34C or 11/83 to the
MODCOMP - it takes me a while to get "used to" the MODCOMP. MODCOMP also
interprets all operations and logic in HEX as opposed to OCTAL.
Is there a keyboard terminal or screen with it?
It has a RS-232 async port for a console terminal. Other I/O is: Two
additional async ports, one high speed serial link for networking (200KHz)
and a paper tape reader port. There also a "plane" that was built by the
customer that I'm still trying to find docs for in the customers "archives"
with lots of other I/O. BTW: One can attach disks to async ports, too :-)
Interestingly, you can boot from any readable device on the system with the
same boot loader - including async ports! the boot loader is very gnarly -
only 8 instructions long - and it took me hours to figure out how it works
(hint: it uses self modifying code to load a secondary boot which then loads
the program you are booting).
Cheers,
Lyle
-----Original Message-----
From: cctech-bounces at
classiccmp.org
[mailto:cctech-bounces at
classiccmp.org] On Behalf Of Lyle Bickley
Sent: 05 June 2007 05:07
To: General Discussion: On-Topic Posts Only
Subject: MODCOMP II Rescue Revisited...
A number of you probably remember me "announcing" in Jan, 2007 that I
had rescued a MODCOMP II/12 from a lab here in Silicon Valley. The link
for that is below (sorry, it's slow - the pictures are large).
http://bickleywest.com/modcomp.htm
After a lot of work cleaning up both the CPU and I/O chassis I began
checking out the system. It turned out that the I/O chassis was in
pretty bad shape.
I went back to the lab facility where I found the MODCOMP II - looked
through several more buildings - and found another lone MODCOMP II I/O
chassis. I went through the "salvage" process again - and finally picked
it up about a month ago.
It was in a lot better shape than the original I/O unit. And the really
great news - it was an identical configuration to my original I/O
chassis.
After cleaning it up, doing all the usual capacitor, power supply
checking - I powered it up - and everything "looked" good - and no bad
"cooking"
smells ;-)
I cabled up the CPU and I/O unit, powered 'em up - and to my amazement
the front panel controls seemed to work O.K.
I then did the usual hand memory tests - and core memory worked O.K.
every location I tested.
I then wrote a bunch of small diagnostics (in machine code) - and found
that I/O was not easy to code - but I did enough to check that the
console in/out ports worked O.K.
Today I loaded diagnostic monitors, and diags - and most of the system -
including I/O is working! The really good news is that all 64K (words)
of core memory passed the long manufacturing memory diagnostic - which
even tests for "hot cores" failing.
It's been months in the making this critter come alive - but it sure
feels great when the diagnostics tell you that you are on the right
track :-)
Cheers,
Lyle
--
Lyle Bickley
Bickley Consulting West Inc.
Mountain View, CA
http://bickleywest.com
"Black holes are where God is dividing by zero"
--
Lyle Bickley
Bickley Consulting West Inc.
Mountain View, CA
http://bickleywest.com
"Black holes are where God is dividing by zero"