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Interak Z80 Computer

A Z80 based computer, modular in design. Well build and thought out.

melmel
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This is a very old and yet newish project. Back in the early 1990's I began to build a Z80 based computer. The Interak, produced by Greenbank electronics in Liverpool, the attraction for me was you could build it board by board, bit by bit. It fitted in a 3U high 19" rack, you could jump on it without harming it, built like a tank.. But I sold it a few years later and got my first PC. About 2 years ago now someone discovered it in a rubbish skip in cambridge (along with a CPM book with my details inside), where I had sold it to a company. and i was able own it once again..... so I've turned full circle, with a lot of other stuff between..

In the early days programs, like on other "HOME" computers were saved and loaded to/from a standard cassette recorder, this seemed to work fairly well, but on some machines a program saved on a hot day, may not load on a cold day. The clock frequency (often a simple NE555 circuit ) drifted with temprature. The Interak circuit was much better then this, using an AY-3-1015 UART, dual output and relays to switch the recorder motor on and off.

It was not until we had Floopy drives  3.5" 720Kb that we had a choice of Basics and Pascal, "C" etc.  This all ran under CP/M 2.2. Which we still use, even if it's on a Compact Flash card.

InterakSystemNotes.pdf

Full documentaion including, schematics, working notes, history, etc Can be found here, c/o Keith Howell: https://hackaday.io/project/168194-interak-z80-computer-documentation

application/pdf - 8.44 MB - 10/22/2019 at 09:55

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  • Minor Interak meeting 27/10/2019.

    mel10/28/2019 at 15:28 0 comments

    27/10/2019. Well today a few of us got together for a chat and to meet for the first time. We met at the Retro Computer Museum here in Leicester, they came from everywhere like Liverpool and Wiltshire to mention 2.  We had 4 very different Interak computers there, some working better then others.

    A very nice cased system that Greenbank did for BT, My interak in the background and Andy's far right, trying to fix a floppy disk controller card.

    Alan's Interak is one of the best I've seen, not that I've seen many. The case has extra height, good for displays.  see: https://www.fussylogic.co.uk/~interak/www.interak.co.uk/   My old Interak site is at http://www.melsaunders.co.uk/

    And lastly all of us. Keith Parkins, Andy Collins, Me, David Parkings and Alan Paton

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nexxo00 wrote 11/08/2019 at 20:43 point

(tears up) It's so beautiful!

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alcmcintosh wrote 11/07/2019 at 01:27 point

Nice! Just looked at a Z-80 cpu card with 64K memory with the Motorola 6845(?) Video chip. Also have a batch of programs to support it. Had plans to add a 256 byte paging system. Had the card connected to a minicomputer for mass storage and downloading the os and app programs. Mostly assembly programs.  Card is wire wrapped. Nice to see there is still an interest in the Z-80...

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mel wrote 11/07/2019 at 09:09 point

Hi alcmcintosh! I like it.  I am just looking at on old Elektor cct for an 80 col VDU also using the MC6845, 64 cols at present but most CP/M stuff is for an 80 col screen. also need programmable graphics. We have schematics etc..

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Gerhard Schmidt wrote 11/06/2019 at 21:40 point

Hi. Looks like my homebrewed 1984 Orwell-Z80-system with ORWELL-DOS operating system in assembler, with ten Euro-size cards, 64-pin bus-system, 8-inch-Floppy-controller, 512*512-pixel B/W graphic controller,  4*32 k EPROM for the operating system, 4*8 k SRAM for battery-buffered data and 32 k dynamic RAM for data.  See http://www.gsc-da.de/orwell/orwell.html for the hardware (in German only). brgs, gsc

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Jim Thompson wrote 11/06/2019 at 18:10 point

Do you know if the physical arrangement is compatible with Eurorack (the modular music synthesizer system)?  (5.08 mm (0.2") horizontal spacing between centers of 3 mm threaded holes, and 122.5 mm (4.82") between centers vertical spacing.)  It LOOKS the same, aside from depth from the front panel, which is much greater than most Eurorack cards, and I think that Eurorack got its physical arrangement from generic card mounting boxes produced in the 1980s.

I've been toying with the idea of using Eurorack for amateur radio modules (VFOs, synthesizers, IF strips, mixers, audio preamps and amps, using better connectors (no 3.5mm plugs for RF!!)), and it would be great if a microcomputer standard fit into the same physical space.  Do you know what type of connectors are used?  And are these on ribbon cables (like Eurorack), or are they on a backplane that dictates a particular card depth?  I mean, it SEEMS like even if there is a standard depth, the backplane could be implemented with ribbon cable - just a thought.

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bert.hoogenboom wrote 11/06/2019 at 19:30 point

There many card racks of this kind 19 inch wide 3HU means the cards that fit in there are 100 x 160 mm

I used this rack in 1980 to build a z80 system that is still working today

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Neil Johnson wrote 11/08/2019 at 10:03 point

Eurorack (the synthesizer format) is based on the Eurocard subframe format as used by these computers.  Dieter just used standard parts from the likes of Rittal, Schroff, etc, to keep costs down.

What these rack mount computers use is a common backplane to carry power and the address/data/control lines between the various cards (CPU, IO, VDU, floppy, etc).  This is how this case system is supposed to be used.  The Interak uses an edge connector backplane, the alternative is the DIN41612 connectors, which are also typically mounted on a backplane (see VMEBus or STEBus systems).

The Eurocard format (100mm x 160mm) is designed to exactly fit into these frames and support an DIN41612 connector to the backplane.  There is a wide variety of DIN41612-compatible connectors, some up to 96 pins, some with RF connectors, some with power spades, and some have combinations of all of these.

19in subracks are used extensively in the comms world.  So amateur radio should feel right at home there!

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julian wrote 11/05/2019 at 11:41 point

Mine's been in the shed for 18 years - just starting to power it all back up (cautiously).

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Dan Maloney wrote 10/23/2019 at 15:49 point

You had me at rack mount...

I never heard of this one at all. That modular design is cool. Looking forward to progress.

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