Date   : Tue, 05 Mar 2002 15:42:34 +0000 (GMT)
From   : jim <jim@...>
Subject: Re: Xfer

On Tue, 5 Mar 2002, Richard Gellman wrote:
> There is (I think, dont quote me) a circuit diagram on TBL! (if not, on a
> similar well known BBC site, try the bbc documentation project) showing the
> Acorn 1770 FDC upgrade board.

It certainly exists, because I'm looking at it. Can't remember which site
I got it from though ... Ah. A quick google says it's the beeb doc
project, http://members.aon.at/~musher/bbc/hardware.htm , third entry
down. Big GIF. The "drive control register" is just a 74LS174 which
latches the low 5 data bits through to drive/side select / density / FDC
reset. 

> The only other problem you would encounter, is having to switch DFS ROMs, as
> the 8271 and the 1770 are accessed completely differently.

As Chris said, they ought to cohabit quite happily. I have a beeb with
8271 disc upgrade but I use the 1770 DFS as well to talk to the Tube,
since I have an old 8271 DFS without Tube code.

jim
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