Date   : Thu, 19 Apr 2007 11:39:56 +0100 (BST)
From   : debounce@... (Greg Cook)
Subject: BBC B progs on a B+128k - any known problems?

On 17 Apr 2007 20:49:59 +0100, Jonathan Graham Harston
<jgh@...> wrote:

> It needs to disable masquading at some point as Z-Break puts a JMP
> sequence in the middle of page &10 - even when page &10 - the
> *shared* workspace - isn't owned by DFS!!!! I've had so many
> problems trying to stop OSWORD &7F trampling all over page &10
> when it doesn't own it that I'm strongly tempted to change the
> documentation to say "&10xx - reserved for DFS and OSWORD &7F".

Yeah, I've seen it cause problems.  To fix it the DFS should only need
to claim the workspace (and restore its contents) on receiving disc op
calls, shouldn't it?  Other ROMs should then be aware that they may
lose the workspace when making these calls.

If the DFS can't be patched then the workspace *will* be corrupted when
the user calls OSWORD &7F etc., but other ROMs can anticipate the
damage and relinquish it temporarily when they make the call themselves
- effectively reserving 'shared' workspace for the DFS, as noted!

Greg Cook
debounce@...
<http://homepages.tesco.net/~rainstorm/>


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