2650

This Signetics 2650 board was my first ‘computer’ dating to the 1970’s. My close friend and a tutor at the University of Canterbury, Martin Lindley and I shared the costs of setting up the 2650 development system and found a ‘dumb’ terminal so we could learn to program these new processors. At that point I would have been working for Computer Bureau Limited, later CBL and then Datacomm.

Martin had been a year ahead of me at University. He stayed on in the Computer Science Department and I went to work writing software and later running the Systems Department.

At that time Martin would have been doing most of his work in Algol on the Burroughs B6700, which was still quite new to the University.

I had returned to University in Year 2, having done my first year as Engineering Imtermediate, then taking a year off to spend working in Blenheim, then a year with ICL in Wellington, then back to Computer Science at the University of Canterbury in 1974. By a strange coincidence, my professor in the department was Prof John Penny, my own name but mine is spelt Penney.

Above: The Signetics 2650 development board, an Electronics Australia project. The board code is EA 77up2. The 77 suggests 1977. I have a near-complete set of Electronics Australia, so I’ll have to get them sorted out and find the original article. I should have the kitset documentation somewhere too (kleptomaniac...).

The large white chip on the left is the 2650 microprocessor, coded S7102 and 2650I. The other white chip is a 2608 PROM containing the PIPBUG program, used to develop programs. The two small grey chips on the right are 2112 RAM chips, each 256 bytes x 4 bits. The chip top centre is a 74123 used as a clock generator, the potentiometer above it allowed the chip speed to be adjusted to get the 110 baud TTY interface locked in correctly.

The chip top left is a 74L00 which in turn drives the usual 1488/1489 serial line chips (on the separate board). The serial interface had it’s own pair of 9 volt batteries to provide the 9-0-9 volts (it should be 15-0-15 but most terminal interfaces are quite forgiving). The 2650 board ran from 5 volts provided by another battery. I think we ran it on 4.5 volts actually.

The dumb terminal plugged into the DB25 connector on the left.

The 2608 provided 1K bytes of ROM while the 2 x 2112 chips made up 256 bytes of RAM. There was no program storage, although somewhere deep in the recesses of my tiny brain I recall finding a way to store programs on tape.

All programming was in assembler, PIPBUG assembled that into machine code and ran the result. The most complex program we managed was PONG (what else in that time frame?). For those who never played Pong, it was the original ping-pong and very basic but a lot of fun, especially when you wrote it all by yourself.

And no, it didn’t run on a TV console. It ran on the dumb terminal. I think we used to borrow one, since neither of us had the cash to own one (around $2000 I think). It would have been a DEC vt50 or vt52 probably, or maybe a vt100 (which were considerably smaller and lighter).

I’m pretty sure I own a VT220, a later model. I bought a VAX system a while back and it came with a terminal.

So, that’s the story of the 2650.