Date   : Fri, 24 Oct 2008 12:27:09 +0100
From   : pete@... (Pete Turnbull)
Subject: A500 development ROMs

On 24/10/2008 11:01, michael.firth@... wrote:
>> From: bbc-micro-bounces+michael.firth=bt.com@... 
>> [mailto:bbc-micro-bounces+michael.firth=bt.com@...
> .uk] On Behalf Of Adam Sampson

>> Pete Turnbull <pete@...> writes:
>> 
>>> I'm sure the reason you think there was an A500 copro is simply
>>> that early on, the A500 needed the Tube and a Beeb to do I/O/.
>> 
>> There are some pictures of an "A500 second processor" board here
>> that looks distinctly different from a regular A500 motherboard:

>> It appears to have video, audio and keyboard interfaces, but no
>> disk controller...

Looks like I have to eat my words :-)  I saw plenty of A500s while I was 
at Acorn (1986 to 1990) but not that board.

> Given that Acorn presumably made their PCBs in house, it may be that
> the Acorn A500 second processor was a half-way house system between
> the ARM Evaluation System and the A500 standalone machine.

They were designed and laid out in house, but the actual etching, 
drilling, etc was contracted out.

> As Pete Turnbull has already said that the video circuitry was
> brought up first and then the keyboard, and it looks as though the
> A500 second processor has the video and keyboard circuitry, then a
> few of these boards were probably produced to allow the firmware
> designers to get on with things while the rest of the A500 PCB was
> laid out.

That's plausible.  It's a pity the scan of the circuit diagram isn't 
good enough to read the date.  Another possibility is that a few were 
made as a cheap(er) software development system for third party 
application developers, although the ones I met used A500 computers.

Chris's webpages state that his A500 came from Paul Fellows; for those 
who don't know, Paul was the leader of the software team that produced 
Arthur etc.  One of the pages also says Chris got his A500 second 
processor from Mike Harrison; Mike did some work for Watford Electronics 
(when he was a student, I think), built the first video digitiser for 
the Archimedes, and did some demo software which was used at the launch 
in July 1987 and for subsequent dealer and LEA demos.

-- 

Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York