Date   : Mon, 15 Sep 2008 21:08:59 +0100
From   : mfirth@... (Michael Firth)
Subject: Sideways RAM rom ?

----- Original Message ----- 
From: "Phill Harvey-Smith" <afra@...>
To: "Michael Firth" <mfirth@...>
Sent: Monday, September 15, 2008 8:29 PM
Subject: Re: [BBC-Micro] Sideways RAM rom ?


> Michael Firth wrote:
>> ----- Original Message ----- From: "Phill Harvey-Smith" 
>> <afra@...>
>> To: <bbc-micro@...>
>> Sent: Saturday, September 13, 2008 9:34 PM
>> Subject: [BBC-Micro] Sideways RAM rom ?
>
> [Snip!]
>
>> The later standard was to use the Acorn 1770 DFS which came with a set of 
>> SRAM commands, and which was also the provided way to load the SRAM on 
>> the Master.
>
> Yeah I noticed that, I've been using the master to verify that my DFS disk 
> writing program was working, by writing a rom and loading it into
> the SRAM, I believe the B+ also has it doesn't it ?
>
>> I've just uploaded the Utilities ROM I mentioned in another post to 
>> http://www.firths.org/bbc/UtilsROM, this ROM allows the use of the SRAM 
>> commands on a machine that doesn't have the 1770 DFS installed. It does, 
>> however, increase PAGE by &200.
>
> Cheers, that seems to work and do what I need now, and I've just finished 
> dhaking the bugs out of the hardware, so now have a machine with 8 sram 
> banks 0..7, and 8 ROM banks 8..15, guess batter backup will be the next 
> step :)
>
You are right that the B+ tends to have the SRLOAD commands available, at 
least on
the B+128k versions. The original 64k B+ came with an earlier version of the 
1770DFS
that didn't have the SRAM support (as it didn't have any SRAM banks)
The B+ does have a different mapping for the W,X,Y,Z aliases from the 
Master, on the
Master these map to banks 4,5,6 and 7, while the B+ maps it to either 
12,13,14 and 15,
or 12,13,0 and 1, depending on whether the second half of the SRAM is at the 
top or
bottom of the ROM space (it sits at one end, and BASIC at the other)

Out of curiosity, how similar is your project to the one documented at?

http://homepages.tesco.net/~rainstorm/bmem.htm

Michael