Date   : Thu, 21 Sep 2006 09:28:56 +0100
From   : "David Harper" <dl.harper@...>
Subject: Re: 80186 board in Master

Jules Richardson wrote:

> Anyone know how many were built? I got mine years ago and despite masses
> of Acorn 'finds' since (including lots of rarities) I've never seen
> another M512 (although I don't doubt that they sell on the likes of ebay
> every once in a while)

According to Robin Burton (Master 512 Forum, Beebug, May 1991) about 13,000
M512s were sold. It seems that a large number of these were never used as
Master 512s (Some speculations about this at:
http://www.cowsarenotpurple.co.uk/bbccomputer/master512/problems.html)

> There was a memory upgrade board for them - I believe one listmember has
> one, but that's the only surviving example that I've heard about.

There was a memory upgrade to 1Mb produced by Solidisk and called the
"PC-Plus". After Solidisk stopped producing it, Robin Burton sold a similar
product for a while through this company "Essential Software" (the only
Master 512 software house ever!). I have one of these, and I have just put a
picture at:
http://www.cowsarenotpurple.co.uk/bbccomputer/master512/pictures/ess1mb.jpg

As you can see from the photo, this is a fairly simple piece of electronics,
and can be tackled as a DIY project (provided you can get hold of the
parts). Full instructions are in Appendix G of Robin Burton's "Master 512
Technical Guide", which is online at:
http://www.cowsarenotpurple.co.uk/bbccomputer/master512/bibliography.html#m512tg

> I've got no idea why Acorn went for the 80186 CPU; they'd already built
> the 80286 copro for the B/B+ (as used in the ACW 3xx machines) so I don't
> know why they didn't make an 80286 internal copro (with less memory so the
> board would fit) for the Master. Maybe just a cost thing?

My feeling is that they had gone so far with the project in partnership with
DRI that they couldn't back out.

David Harper