Computer Specialists Ltd - Z80 Board

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Computer Specialists Ltd - Z80 Board

Postby TRS80 on Tue Sep 11, 2012 11:00 pm

Has anyone come across Z80 boards made by Computer Specialists Ltd?

I was recently given a board labelled CS-C-16/64-C from Computer Specialists Ltd... Made in New Zealand it says. Serial number 30, Copyright 1982 is stamped on the board.

It looks to be a fairly conventional Z80 machine with SIO, PPI and programmable clock chips plus 64kb of 4864 dynamic RAM. There are three ROMS labelled CSMON v4, CSBASIC R1 and CSBASIC R2.

I and will try to get it running.


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Re: Computer Specialists Ltd - Z80 Board

Postby Gibsaw on Wed Sep 12, 2012 11:17 am

I'm not familiar with it, but that sounds like it'd be of interest to one of the nz computer museum groups.
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Re: Computer Specialists Ltd - Z80 Board

Postby Radar on Wed Sep 12, 2012 11:49 am

Thats a nice bit of NZ Computer history and Computer Specialist's are actually still in existence - these days as Compuspec.

The history of the company and there early systems is mentioned in this (extremly interesting) presentation:
• Preserving our IT Heritage: Computers Designed & Assembled in NZ (Preserving our Heritage NZ-made Computers) B. Doran, A. Trotman (2010)
New Zealand Computer Society Conference: Celebrating 50 Years of ICT Innovation
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Re: Computer Specialists Ltd - Z80 Board

Postby falco on Sun Sep 16, 2012 3:31 pm

Well, that PDF was a real trip down memory lane for me. Paul MacDiarmid was a friend of mine (very sadly now passed away), and I know Bob Doran too (donated some machines to his collection). And the picture of the computer lab at Auckland Grammar is of the lab I used regularly. Fascinating. I'm still curious what those printing terminals were.
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Re: Computer Specialists Ltd - Z80 Board

Postby Carcenomy on Sun Sep 16, 2012 7:08 pm

Hey Radar, any contact details for these two university chaps?
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Re: Computer Specialists Ltd - Z80 Board

Postby TRS80 on Sun Sep 16, 2012 10:12 pm

Details for Andrew Trotman are at

I have had an email discussion with him last week about the board and he sent me a bit more information about the company. The don't seem to have advertised the "Decade" machine in any of the Bits and Bytes magazines. Given that it was more business focused they may have advertised in Interface (the New Zealand Computer Society magazine from the 80's). Auckland library has a collection so I will try to get past this week and have a look.

I am not 100% sure this is a decade board. The friend I got it from suspects it may be from an embedded controller rather than a full computer although the hardware is sufficient to be a stand alone Z80 machine... just needs some storage.

A cellphone quality photo of the board is here....

It needs the Xtal and the TTL/RS232 level converters replaced but otherwise looks complete.

I had an initial look at the monitor ROM disassembly to work out it uses the onboard serial port for a console. Still a little way to go. The few spare "play with old computer" minutes this weekend were spent debugging the PDP11.
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Re: Computer Specialists Ltd - Z80 Board

Postby TRS80 on Mon May 05, 2014 11:33 pm

Finally got clear enough of TRS-80 projects to spend some time getting this board going.

The boards were made in NZ and sold as a "controller" but also as a basis for a complete Z80 machine with a disk controller.

I don't know the history of this board. There are hand written comments on the documentation about "Pye TV's" and "Sheraton Rotorua" and I had an email discussion with Mark Eaton at Compuspec (the manufacturer still exists) and he said some of these boards were used to drive information screens in hotels.

I only have the main PCB which had been burgled for a few parts but thanks to the documentation it was actually pretty easy to get going.

Needed a replacement 4.9152 mhz xtal for the STC (AM9513 System Timing Controller). This is used for the real time clock but more importantly the clock for the SIO (Z80 SIO/0 serial IO controller). Also a clean up around the reset circuit. Looks like a reset switch or something was removed so the board by someone with a plumbers soldering iron so it wasn't in great shape there. The serial level converters needed to be replaced (MC1488 and MC1489) although they may never have been fitted because the CTS pullup resistors were not fitted to the board (more on that below).

It took some digging into the ROM to work out why the CPU seemed to run and the STC was configured to generate the correct SIO clock frequency but nothing appeared in the terminal.

Two things.... the console is actually on port B of the SIO (not directly stated in the documentation although implied by the pinout on the serial header).

Also because the CTS pullup resistors were not fitted. These pull the CTS lines at the serial connector to +12V which is inverted by the MC1489 to be "active low" for the SIO /CTSA and /CTSB signals. Without the resistors these signals are +5V and the SIO won't transmit anything.

So it works. Monitor ROM and Tiny Basic both run and work as documented.


Really nice little board and a real piece of NZ computing history. I have scanned the documentation so will post it on my blog should anyone else come across a Compuspec board and want to get it going.
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