[BBC-Micro] Some Beeb addons

[Pete Turnbull]

On 06/03/2007 09:44, chris whytehead wrote:

>> does this card effectively make my B a B+?
>>
> According to the Acorn Brochure advertising the B+, the differences are:
> - 6512 processor
> - 64K RAM 48K ROM (*)
> - Disc interface (WD1770)
> - 6 ROM sockets
> - Improved buffering (*)
> - New DFS commands (DFS 2.10)
> - Shadow screen (*)
> - Fully Compatible OS (MOS 2.00)

There's a bit more to it than that, and some differences of detail: for 
example, that's why the GXR (Graphics Extension ROM) for the B is not 
the same as the one for the B+.  Acorn Factsheet 2 lists the differences 
they told dealers about, and it's 4 closely-typed A4 sheets, though much 
is just the obvious differences like different value for MOS type in 
Osbyte 129.

The WE board certainly doesn't turn a B into a B+.  The osbytes that 
deal with screen differences aren't the same, the extra 12K of RAM (over 
the 20K for the shadow screen memory) is used differently, and OSWRSC 
isn't implemented (but does anyone use that?).

-- 
Pete						Peter Turnbull
						Network Manager
						University of York