1 Feb
2010
1 Feb
'10
2:51 p.m.
Tony Duell wrote:
Git ;) Was the 80-col VDU just the stock System one (Acorn p/n 200,019), or
something else? I've got at least one of the System ones (along with many of
As far as I know it'sjust hte standard System one. The 6809 and 6502
buses are very similar, so there'd be no need to have special cards for
the 6809. Certainly the memory and FDC cards are the normal ones.
No... I
spent many a year searching, too. I have the manual, which I think
includes the schematic (if not, I got that separately), but I never did come
across the physical board.
You're going to hate me. I've got _2_ of them. One with the normal ROM
for the 40 column VDU card, the other with a ROM for the rare 80 column
VDU (and yes, I have that card too). the other System boards that they made). The 6809 CPU
board has always proved
elusive, though...
I've never heard of another 80x25 board than the '019 one, but I think my
System-era document collection's only about 80% complete so I might be missing
something!
There's one under my bed (seriously). Alas I don't have the disk unit,
which makes it farily useless (the ROMs in mine are simply a disk
bootstrap).
Yes, I remember you telling me about it... I recall the museum being offered
one quite a few years ago, but then the donor went all quiet (as sometimes
happens!) so I've never seen a 'live' one.
Was there something unusual (local processor or strange interface etc.) about
the disk unit that makes it hard to just couple some drives up?
The disk cotnroller was in the drive unit. The connectors on the bottom
of the Tiger are essentially system buses (and all 3 are differnt -- I
think 2 of them carry differen subsets of the Z80 bus, the other one the
6809 bus, but I might be mis-remembering it).And I don't have schematics
of the disk controller board. I suppose I could disassmeble the ROMs and
see what sort of FDCchip it's probalby looking for and at what address,
but I've got a lot of other projects to complete first.
The curious Tiger used a 68B09 for I/O (along with a
Z80A for the main
processor and a 7220 graphics chip).
The HH machine? I've never seen a real
one, but it sounded like an interesting
beast. Remember
that there was a *lot* of in-house expertise in 6502 development; the
Atom was almost a "System rack in a home computer box", just as the BBC was an
To the extent that the expansion bus was a System bus connector. You
could fit one System eurocard inside an Atom -- at least one of my Atoms
has the econet interface doen that way (another one of my Atoms has the
'proper' econet interface PCB plugged into the solder side of the mainboard).
a System FDC, as I'm sure you know). I've seen
two different board layouts for
System Econet cards, incidentally.
My guess is that it's the connector for a parallel-interfaced keyboard,
thus putting human input and output on the same PCB.
-tony
The video ciorcuitry was very differnt, though.
THe Atom used the 6847
VDG chip. The System VDU cards used 6845s, and in the case of the 40
column one, an SAA5050 teletext charactger geenrator ROM.
Yep. I always wanted to build a colour encoder board for the Atom (I've got
the documentation, but never had the physical board) but maybe that's
irrelevant now I'm in a non-PAL country :-)
Oh, I've got a couple of Control Universal "CU Graph" graphics boards with
a
System bus. These use the EF9366 graphics display processor for the "grunt
work". There are two boards in each set, one containing the I/O decoding
logic, 9366 IC, 16KB of DRAM and video outputs, the other containing 32KB of
DRAM and a mysterious* 26-way IDC connector brought out to the card edge.
According to the EF9366 docs, the boards should do 256x512 in 8 basic colours.
* I don't have proper documentation for them and have never traced a schematic
out. I wondered about light-pen connectors (and the 9366 chip does support a
light pen), but 26 pins seems a bit excessive. Maybe they just bring some
other useful signals out to that connector.