16 Jul
2002
16 Jul
'02
3:04 a.m.
OK, duh, I overlooked the front panel picture where there are connectors for
all those ports, making the boards' functions kinda obvious.
----- Original Message -----
From: "Jim Kearney" <jim(a)jkearney.com>
To: <cctalk(a)classiccmp.org>
Sent: Tuesday, July 16, 2002 10:17 AM
Subject: Re: Mark-8??? Popped some pictures up.
Looking at the custom boards, it looks to me like:
- the boards mounted to the address latch are a cassette interface. The
one
on the right is the modulator/demodulator and the one
on the left appears
to
generate various pulse widths. It's a little hard
to make out the chip
numbers.
- the one on the input board adds 7 input ports
- the one on the output board adds 3 output ports
I think the crystal is missing... I don't see any added parts that would
suggest an oscillator.
It's possible, since the builder made all these new boards, that he or she
hand-made the Mark-8 boards from the construction booklet too, making it
even more rare.
----- Original Message -----
From: "Andy Berg" <groovelists(a)yahoo.com>
To: <cctalk(a)classiccmp.org>
Sent: Monday, July 15, 2002 11:52 PM
Subject: Re: Mark-8??? Popped some pictures up.
Very nifty!
It is so amazing to have such knowledgable people a
click away - you all are great! :)
I promise I'll stay away from the pots. I don't know
exactly what my immediate plans are for the fellow,
ahm... I'd love to get it up and working sometime.
I'll peer about online and see if I can scare up a
suitable surplus power supply of some type. This is
perhaps the oldest machine I've had the chance to work
on... I'm quite excited, but, I think somewhat
rightfully, nervous.
Oh! I don't know if anybody would like such a thing,
but I put a little bit clearer picture of the CPU up
at:
http://66.30.18.171/MARK8/CPU3.jpg (Big file warning:
~420K)
--- Loboyko Steve <sloboyko(a)yahoo.com> wrote:
This does look like a Mark-8 that's been
modified
(rather craftily) to use a plug backplane.
I'll bet the control socket on the front is where
the
Front panel (or maybe EPROM or ROM or maybe even
diode?) board would go. Keep in mind that ROMs of
any
kind were very expensive in 1974-6 for a home
budget,
and no one had programmers.
There's a lot of glare on the 8008 CPU but I think
this is an example of a VERY early package (there
are
at least 2 types of C8008 packages).
If you actually intend to get this going, I'd be
concerned about the Molex sockets. They are
constructed using PURE EVIL and were unreliable when
new. Judging from the chips utilized (some no-name
chips) and the sockets I suspect that this was built
by a very skilled hobbyist, probably an engineer or
senior technician working at home.
Also, definitely check that you have +5 and -9 on
the
8008. You could damage it with one missing (and
never
mind the 1101's).
Someone mentioned to me at the xtal on the mark-8
was
optional, and you might have an RC oscillator and
one-shots on there instead. The clock was 2-phase
and
would require a scope to adjust so if you see pots
don't adjust them.
Thanks for the terrific PDF - I was hoping that some
kind person might've put the scans up as you did. Some
bedtime reading material, I think.
and --- Jim Kearney <jim(a)jkearney.com> wrote:
Definitely a heavily modified Mark-8. Look at
the
board prints towards the
end of http://www.jkearney.com/8008/Mark-8.pdf
Thanks again for everything!
Andy
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