Date   : Fri, 29 Sep 2000 09:33:20 +0100
From   : "Fraser, Colin J" <colin.fraser@...>
Subject: Re: 1770 disc interface

> -----Original Message-----
> From: Mike Tomlinson [mailto:mike@...]
> Sent: 29 September 2000 06:44
> To: bbc-micro@...
> Subject: Re: [BBC-Micro] 1770 disc interface
> 
> In article <39CFA3C6.C63EE023@...>, Philip Peake 
> <philipp@...>
> writes
>
> >Can one do a straight swap WD1770PH for WD1772PH? 
> 
> yes, but the step rates are different - Acorn did at one point change
> the 1770 chip on the BBC upgrade for a 1772. (The rom stayed 
> the same.)
> The jumper links on the keyboard changed and the fitting instructions
> detailed what the links needed to be for both the 1770 and the 1772.  
> 
> Unfortunately, the copy of the instructions at the doc project don't
> include the addendum sheet for the 1772 and I can't find a copy of it.
> The default step rate for the 1770 was 6mS, on the 1772 with 
> the default
> liks it's 3mS, which is too fast for 5.25" drives.

I've got an Acorn 1772 board in one of my beebs, which I picked up a couple
of years ago, unused in the box.
I'm sure it had the addendum sheet so I'll see if I can find it and scan it
in.

Colin f