Subject: Practical Electronics CHAMP/Tangerine Microtan 65

From: David Comley <[email-masked]>
Date: Tue May 20 21:52:00 2003

Many years ago Practical Electronics in the UK
published the design of a microprocessor-based system
called the CHAMP. If I remember rightly it was built
on Veroboard. I remember reading the articles in the
school library and wishing I could build one.

Did anyone ever build one of these ? Do the plans
still exist anywhere ?

Also, I'd like to re-acquaint myself with the Microtan
65 which was one of the first systems I ever owned.
Are there any systems still in existence ?

Dave.
The New Yahoo! Search - Faster. Easier. Bingo.
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From: "Rob O'Donnell" <[email-masked]>
Date: Wed May 21 02:26:00 2003

>Did anyone ever build one of these ? Do the plans

Hmm.  I have an unsorted mass of PE mags dating from the mid-60's through 
mid-80's in boxes in the spare room; have you any idea of the rough date of 
this?  Boxes are at the bottom of a pile (typically, but they are heavy..) 
but I have to move them in the next few weeks anyway, so can take the 
opportunity to skim through them.

Rob.

>Are there any systems still in existence ?

ah, I remember looking at the ads for these ... finally ended up with a 
zx81 kit (worked first time, too!).

Rob.

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From: David Comley <[email-masked]>
Date: Wed May 21 07:43:01 2003

> opportunity to skim through them.

I think it would have been published around 1978 or
1979. I had one of the articles - but I think the
design spanned several issues. It would be great if
you had the full set !

> zx81 kit (worked first time, too!).

I still have my ZX80 which preceded the Microtan. I
don't count it as my first system though because once
I built it I didn't do anything with it. It just sat
there. 

Dave.

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From: [email-masked] (Tony Duell)
Date: Wed May 21 17:50:31 2003

> on Veroboard. I remember reading the articles in the

One large piece of veroboard (stripboard for those across the Pond :-)) 
on top of the case for all the logic (that way you coupld probe at all 
the IC pins without extender cards). Another somewhat smaller piece of 
veroboard on top of a similar case for the CHAMP-PROG (1702 Eprom 
programmer). This was a 4040-based machine, of course.

> Did anyone ever build one of these ? Do the plans

I should still have all 10 artictles for the CHAMP, CHAMP-PROG and 
CHAMP-UV (EPROM eraser). But don't even think of building one now -- just 
about all the LSI parts (CPU, RAM, memory interface, EPROMs, etc) are 
almost unobtainable.

-tony

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From: David Comley <[email-masked]>
Date: Thu May 22 07:50:01 2003

> about all the LSI parts (CPU, RAM, memory interface,

That would certainly add to the challenge of building
one, not to mention the timeframe. I did see a 4040
and some 1702's on ebay the other day. Could the other
parts be emulated somehow ?

Dave

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From: [email-masked] (Tony Duell)
Date: Thu May 22 15:19:34 2003

> parts be emulated somehow ?

Oh, quite probably (data sheets for them exist). But why bother? Either 
make a simple 8 bit single-board machine round a common processor (6502, 
Z80, 6800, 6809) which will use commonly-available memory and I/O chips, 
or make a processor from scratch (either using TTL, or if you insist, an 
FPGA). Either is more fun and less work than trying to get the parts for 
the CHAMP, and then finding you've blown one by making a wrong connection 
and that you can't get a replacement for it...

-tony

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From: David Comley <[email-masked]>
Date: Thu May 22 16:40:01 2003

> and that you can't get a replacement for it...

Since you mention it, I had been thinking about
designing and building a processor from scratch from
TTL devices. I am slowly accumulating TTL chips as I
come across them at hamfests and things. Perhaps it's
time to put pencil to paper.

Of course I could take the NASA Apollo Guidance
Computer approach and build everything welded-cordwood
style out of NOR gates.

Dave

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From: [email-masked] (Tony Duell)
Date: Thu May 22 16:55:00 2003

> TTL devices. I am slowly accumulating TTL chips as I

It's not that hard. There have been several commercial 12 or 16 bit 
processors built using appoximately 100 TTL packages (perhaps with some 
small PROMs as  control store too). Designing such a processor is not a 
difficult job either...

-tony

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From: ben franchuk <[email-masked]>
Date: Thu May 22 18:58:00 2003

> Computer approach and build everything welded-cordwood

Nope that used lots of REAL ( expensive ) TTL.
The neat part of that was the CORE memory used.

Any how a real TTL computer is about 4+ large
logic cards. Control card, alu card, memory card
and serial I/O card. The mother board is bus
and front pannel logic.
I am doing a 20 bit CPU with about 125 chips total
in the computer and front panel. About 50?
more chips for memory and serial i/o.

http://www.jetnet.ab.ca/users/bfranchuk/ldp/ldp1.html
Ben.

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From: Brian Chase <[email-masked]>
Date: Fri May 23 03:16:00 2003

> small PROMs as  control store too). Designing such a processor is not a

I'd really like to design and build a PDP-8 clone, since the real
ones command such hefty prices on eBay.  I've mostly given up on
getting my own 8/F or 8/M.

It's a simple enough architecture that it could be done without
too much trouble.  And I'd have the benefit of being able to make
use of the exisiting library of PDP-8 software.  The difficult
parts are a) knowing where to even begin, b) finding the time to
figure out how to do it, and c) finding the time to actually do it.

-brian.

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From: Ethan Dicks <[email-masked]>
Date: Fri May 23 08:58:00 2003

> getting my own 8/F or 8/M.

If you are after the experience of having a PDP-8 clone, not the
experience of designing your own from scratch, there's the SBC-6120
at http://www.sparetimegizmos.com/  I don't know if there are any
boards left (we had a group buy some time ago, pictures of mine are
at http://penguincentral.com/retrocomputing/pix/sbc6120/ )
The New Yahoo! Search - Faster. Easier. Bingo.
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From: Ethan Dicks <[email-masked]>
Date: Fri May 23 09:07:01 2003

If you are after the experience of having a PDP-8 clone, not the
experience of designing your own from scratch, there's the SBC-6120
at http://www.sparetimegizmos.com/  I don't know if there are any
boards left (we had a group buy some time ago; pictures of mine are
at http://penguincentral.com/retrocomputing/pix/sbc6120/ ), but it's
a nice little machine that is easy to get up and running.  I'll be
demoing mine at a computer history exhibit at a science fiction
convention this weekend (alongside a PDP-8/L w/ASR-33 and PC04).

The CPU is an Intersil/Harris 6120 - commonly described as a PDP-8/e
on a chip.  They are still available, new, for about $50.  There's
also the 6100, available much cheaper (several listmembers purchased
them by the *tube* recently), but the 6100 lacks on-board EMA support,
among other things (it used a 6102 in the VT-78 for that). 

If there are no more SBC-6120 blank boards available, it's possible to
order your own (expensive for small runs) or use the schematics as a
starting point and build your own with wire-wrap or point-to-point.
Everything on the SBC-6120 is available from modern stocks, although the
64Kx4 SRAMs (6408?) are somewhat hard to find now - rolling your own
design means being able to use just about any SRAM you can find.  It
does require three GALs, though there are people on the list who can
provide them for a nominal cost (2 x 16V8 + 1x 22V10).  It's a fully
CMOS design - mine draws 175mA, and I have run it off of batteries. 

The only thing it "lacks" at the moment, compared to a PDP-8/e is
non-volatile main memory (but some -8s had MOS anyway, not core), and
blinkenlights.

Alternately, there are a few projects out there you could borrow from
to implement a PDP-8 core in an FPGA.  Because of the simplicity
and the extensive documentation, it was frequently assigned as a
student project.

Good luck,

-ethan

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From: Vintage Computer Festival <[email-masked]>
Date: Fri May 23 20:46:01 2003

> getting my own 8/F or 8/M.

Great idea!

> figure out how to do it, and c) finding the time to actually do it.

I'll assume you're talking about the "straight" 8.

There are enough FlipChip modules around that you could probably get 90%
of the ones you need to make the processor and I/O sections without too
much trouble.  The difficulty will be in sourcing the rarer of the modules
(as I have found).

There'll be a lot of wire wrapping.  The front panel can be scanned from
an existing one (I'll be happy to provide you with a scan once I've got it
completed) and then taken to your local printer's and applied to some sort
of base (I'm just having it applied to a thin acrylic base).  The switch
handles will not be that easy to source.  The front panel lamps are still
available from some suppliers.  The plexiglass sides can be manufactured
without a lot of trouble.  You'll have to find a plastic shop that can do
the right bends, and you can find a close enough shade of teal for the
top and trim.  The steel frame will not be too difficult to manufacture.
The power supply should be straight forward for someone with electrical
skill.

The rest is just aluminum trim, switches, locks, etc.

It'll be a lot of work, but very gratifying.

-- 

Sellam Ismail                                        Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger                http://www.vintage.org

 * Old computing resources for business and academia at www.VintageTech.com *

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From: Hans B Pufal <[email-masked]>
Date: Fri May 23 20:57:41 2003

> and the extensive documentation, it was frequently assigned as a

Or tutor's project ;-) I am implementing the PDP-8 in parallel with a 
student doing a PDP-9 for a university project. I'll be publishing my 
design once it runs some serious software....

   -- hbp

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From: Hans B Pufal <[email-masked]>
Date: Fri May 23 20:58:05 2003

Brian Chase wrote:

> figure out how to do it

I have a student text book which describes this in quite some detail. It 
is with my student at this time, I will send you the details next week. 
Poke me if you do not hear by next thursday....

   -- hbp

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From: Brian Chase <[email-masked]>
Date: Fri May 23 22:58:01 2003

> > getting my own 8/F or 8/M.

Heh.  The 8/F or 8/M would be my ideal choices.  They're newer models
but still have proper consoles.  The 8/A has that ugly pushbutton thing.
The older models seem to be so highly sought after by collectors that
they're priced beyond what they'd be worth to me.  I've been looking for
a fairly simple setup, maybe with a papertape punch/reader for I/O to
provide the collection with some blinkenlights and whirring mechanical
bits.

> There are enough FlipChip modules around that you could probably get
> 90% of the ones you need to make the processor and I/O sections
> without too much trouble.  The difficulty will be in sourcing the
> rarer of the modules (as I have found).  [...]

If I were to devise my own, I'd not plan on it being a replica of an
existing PDP-8. I'd just like a functionally equivalent system.  And
probably more importantly than having the machine, I'd like to learn how
to build a non-trivial processor from the ground up.  Along the way I'd
have to pick up the craft of building and testing electronic devices, so
there are lots of nice side-effects.

The SBC-6120 mentioned earlier in this thread is interesting.  It does
have the drawback being that it lacks support for a proper blinkenlight
and toggle switch console.  Also, using a microprocessor seems a bit
like cheating, too, but I can certainly understand it from the
standpoint of being practical for the designer's needs.  At the moment,
given my various resource constraints, I'm torn between going this
route, settling with a PDP-8/A, or continuing on the no-cost route of
using a software based emulator (until a proper system wanders my way.)

Ah well.

-brian.

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From: Vintage Computer Festival <[email-masked]>
Date: Sat May 24 01:22:00 2003

> to build a non-trivial processor from the ground up.  Along the way I'd

Building a PDP-8 replica would certainly give you that experience.

> there are lots of nice side-effects.

FlipChip modules are all discrete components.

--

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From: Hans B Pufal <[email-masked]>
Date: Tue May 27 07:04:16 2003

> getting my own 8/F or 8/M.

See this book for a discussion of the design of a TTL PDP-8 :

"The art of Digital Design"
(An introduction to Top-Down Design)
second edition

		Franklin P. Prosser
		David E. Winkel
		ISBN 0-13-046673-5

   -- hbp