6809 SBC

[Jules Richardson]

Tony Duell wrote:
>> 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).

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 
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!

>>> 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.
> 
> 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?

>> 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).

Indeed - I've seen a couple of Atoms with System lab interface boards 
shoe-horned into the case like that (and my Atom with the disk unit just uses 
a System FDC, as I'm sure you know). I've seen two different board layouts for 
System Econet cards, incidentally.

> 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.

cheers

Jules