Date   : Sun, 13 Jun 2004 10:16:33 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: free memory on a model B with Econet?

Hiya,

More ponderings... how much free memory can I expect for user programs
in a BBC B running in mode 2 and hooked up to Econet?

I'm thinking that I could run the video wall thingy in mode 2, but
double the pixels vertically giving me a 160 x 128 display (which is
probably about right for the aspect ratio of a Cub anyway).

That means I need 10KB of RAM for holding an off-screen image.

Thing is, according to the user guide, anything up to &E00 is reserved.
That not only eats into the 10KB I'd need for an off-screen image, but
gives me no room for any display routine code...

Looking at the memory map for 0 - &E00 there's a lot of vague hand-wavy
'workspace' type stuff though, plus 1KB of langage ROM workspace which I
assume I can stomp on if I'm not using BASIC in the machine?

Indeed, what above &400 is needed when not running a language ROM?

Other option I suppose is presumably I can jumper the BBC to accept a
static RAM chip in place of a ROM in the paged ROM area &8000 -  &C000?
I think I have some 2KB devices spare...

cheers

Jules