[chbot] Vintage computers show and tell...

[Richard Jones]

Somewhere in the garage I have a circa 1978/79 verowire Visual Display pcb
that I developed for Acorn Computers that was the marriage of the Motorola
MC6845 CRTC and the Mullard SAA5050 Teletext character generator IC. Chris
Turner and Roger Wilson at Acorn asked me to develop an 80 character per
line monochrome display for their Eurocard computer range and I offered to
design them colour teletext display instead, which they accepted. Hermann
Houser agreed to pay me with a 6502 CPU, and 8k RAM memory boards. The 6845
and SAA5050 combination became the heart of their BBC computer offering
which won the BBC contract, possibly because of the assumed compatibility
with over the air teletext. I used alternate half cycles of the 6809/6502
phi2 clock to allow the CPU transparent access to the memory mapped display
ram while the character generator used the alternate half cycle for display
access. Heady stuff for its day, given that at work I was using a teletype
to print software listings and a hex keypad to enter programs in hand coded
machine code for the National Semiconductor SC/MP.

I'll see if I can find the board and bring it along to the next meeting.

Richard Jones

On Tue, Sep 27, 2016 at 10:50 PM, Synco Reynders <synco.reynders at gmail.com>
wrote:

> Hi all,
>     The recent thread of Mike needing a floppy drive made me look around
> my office, and I realised I have quite some old computers within arms
> reach... some getting close to becoming museum pieces. Wondering if others
> in the group finding the same and should we have a bit of a show and tell
> next meeting??
> Feed-back?
> Synco
> PS. I've still got my Sharp PC-1251 with printer and microcassette
> recorder (1982). -it's what I learnt to program on. :-)
>
>
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