Mark-8??? Popped some pictures up.

From: Jim Kearney <jim_at_jkearney.com>
Date: Tue Jul 16 09:18:01 2002

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_at_yahoo.com>
To: <cctalk_at_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_at_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_at_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
> _____________________
> groovelists_at_yahoo.com
>
>
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Received on Tue Jul 16 2002 - 09:18:01 BST

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