Made in the UK by Compukit in New Barnet, North London, the UK-101 was originally a copy of the Ohio Scientific Superboard II. Two years and various legal battles later the UK-101 became, technically, behind its erstwhile rival.
You could buy the UK101 as a kit or as ready made for an extra fee. The kit came in a cardboard briefcase, in which there were anti-static tubes containing the 65+ ICs, a box of IC sockets, and bags containing passives (mainly 0.1uF ceramic decoupling capacitors) and keyboard bits (the keyboard switches were soldered directly to the PCB).
The UK101 came with a transformer in a plastic case, which was rectified and regulated down to +5, the regulator's heatsink was far too small and it would run very very hot, causing the RF modulator to drift channel. Many people relocated the regulator off-board onto a bigger heatsink to solve both problems.
It came with an A4-size book authored by Dr. A.A. Berk, covering assembly, trouble-shooting, and circuit diagrams with descriptions.
The UK101 was based around the 6502 processor. On top of ASCII characters, 128 graphic characters were available in ROM. The RAM memory was expandable from 4 KB to 8 KB on board, or 40 KB with an expansion board.
At the time, The UK101 was heavily supported by Watford Electronics in the UK, and by various electronics magazines who published circuits. There were many user groups and plenty of software available. It was thus possible to upgrade this machine beyond all recognision !
Several cases were also made and sold by a number of manufacturers.
Contributors: Paul Mansfield
John reports to us:
There were 3 monitor chips available, this being the 8k rom. The only one I can remember the name of was the Cegmon, the latest in the series.
The 40 pin expansion slot offered some inpressive (for the time) abilites. Mine had a sound card in it but I also saw systems with colour, hard drives and 5.25 floppy systems.
Some boards had links in them in place of the two sockets on your picture. These needed to be removed if you wanted to use the 40 pin expansion and a couple of 8T28s (buffer chips) put in their place. Other expansions I saw included a 'graphics' chip that could be switched in using software. A small pigiback board replaced the Normal character chip (which is the horizontal one in your picture) with the graphics rom and normal character rom slotted into it. This gave 256 additional characters, and since the replacement rom was an Eprom these new characters could be anything.
Programming was via Microsoft 8k Basic and involved a lot of Poke instructions to get it to do anything much. Overclocking was a breeze, but you had to get it right otherwise the screen divided into 4!
Martin Ward adds:
You could upgrade the graphics RAM by "piggkbacking" two new RAM chips on top of the existing chips, with one pin sticking out sideways which had a flying lead soldered to it. This gave you 48 characters x 32 lines.
The tape recorder could also be "overclocked" to 600 or even 1200 baud!
RAM cost about £10 per K (£5 per 1KB x 4bit chip).
Dick Greening reports:
An interesting story is that one of the BBC engineers rewrote the garbage collection routine (in the Microsoft Basic 4 Rom I thing it was,) only to find later that somehow Microsoft had incorporated his routine in their new version of Basic. He was able to prove it was his program as he had encrypted his name in the program!
Sound a familiar story!