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C > CENTRAL DATA  > 2650   


The 2650 was first reviewed in the US magazine Radio-Electronics, in the April 1977 issue.

This computer was supplied in assembled form with an Editor / Assembler. A 12K BASIC was also available on cassette tape or floppy if you had the HD interface.

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In 1977, I was interested in amateur radio and Morse code and wished to build a keyboard to transmit Morse. Designs I had seen seemed to use a lot of ICs and I thought that it would be better to use one of these new-fangled microprocessors which I could program to send Morse and also use for other things.

Most microprocessor board designs seemed to require a separate terminal with even more ICs. However I remembered seeing a design in Radio-Electronics which combined the terminal and processor on the one board and should be cheaper to build.

So I copied the three articles from the April - June issues and read them thoroughly. I did not have enough money to buy all the parts at once, but I ordered the bare circuit board in December 1977 and it took me a year and about $500 to obtain all the parts. Thirty years later I suppose that would be equivalent to about $5000, which seems a lot of money for a computer with 768 bytes of memory! At the time, I recall saying to a friend that I had spent the year building a money sink.

Learning to program took a while and hand assembling with its need for counting relative offsets in hexadecimal led to me counting other things as . . . 8, 9, A, B, bugger . . .

I took me until May 1979 before I first used the 2650 system to send Morse code, but alas, I found that using two hands and the large keyboard on the operating desk were inconveniences which led me to go back to my old keyer.

But I found many other entertainments associated with the computer, building homebrew dynamic memory, NRZ recorder and floppy disk controller.

I later used a Tandy Color Computer before succumbing to the PC. However I later started using PIC16C84s as I remembered having so much fun with assembler with the 2650.

73 VK7RO

Wednesday 3rd December 2008
Richard Rogers (Australila)

I purchased the bare board and components as a kit from Rod Irving Electronics in Melbourne Australia, back in 1976/7 (from memory).

I think the kit was $150. (I worked at Repco Exchange Engines factory for 2 weeks over the summer break to earn the money.) It also came fully assembled for much more money. The young chap (also a teenager) helping me said it wasn''t too hard to put together, hinting to buy the kit not the fully assembled. His boss pulled him aside and chastised him for that comment, wanting to get the higher price :)

Anyway, it had a composite video out, cassette interface and header for ASCII keyboard. I had to purchase the bare keyboard, plus an ASCII keyboard circuit board.

We had an old B/W valve/tube TV that regularly needed the TV repair man to come around and fix - usually just replacing the valves. I told him about my computer kit purchase and he $ped a couple of wires out the back for direct video input.

I built the keyboard board and wired up the keyboard. Built the Central Data board with lots of 74xx TTL chips, RAM, caps and resistors.

First time powering it up (don''t recall what I used for power, could have been a train-set power supply) nothing happened, no output to the display. Using the TV direct video input as a poor-man''s oscilloscope I found that one of the 7400 NAND gates was bad - it should have had a clock signal. There was a free gate on another part of the board so I cut some pins and added some jumper wires. Lo-and-behold, it booted up!

Writing in hex assembler was, let''s say, fun. I didn''t care, this was so exciting for a teenager. Only about 700 bytes were available for programs with the rest of the 2K memory being the memory mapped display. In that 700 bytes I wrote a Space Invaders game. It was functional enough that I spent a lot of time playing it. Programs were saved to cassette.

Threw all the bits in the dumpster when we moved to California in 1992. Wish I hadn''t now :(

Tuesday 27th October 2020
Greg Kilfoyle (San Jose/California $ Melbourne/Australia)

I just bought the board, and injected the RF into the innerds of a TV, Got a keyboard, and got going with the machine code. I remember I stole display memory for program execution and took advantage of half bytes that were identical. I think it could automatically adapt to speed of the morse code, but I can''t remember if it was for receiving for transmitting... I''d like to get one again. Pitched it.

Thursday 4th January 2018
Peter Wotherspoon (Peterborough, Ontario Canada)


NAME  2650
TYPE  Home Computer
YEAR  1977
CPU  Signetics 2650
SPEED  1.18MHz (Xtal of 14Mhz divided by 12), later increased to 4.73Mhz with improved 2650 chips
RAM  2 KB (up to 32 KB)
TEXT MODES  80 chars. x 16 lines
COLORS  Monochrome
I/O PORTS  S-100 BUS, one parallel input port
PRICE  2650 board : $275
16 KB RAM board $289
24 KB RAM board $395
32 KB RAM board $475
Editor/Assembler $20 - Basic language $20

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