Stack Depth requirements for CP/M 2.2 CBIOS

[Chuck Guzis]

On 30 Jan 2009 at 19:08, ROBO5.8 wrote:

> I have rewritten my old systems CP/M 2.2 CBIOS to add an IDE Drive.
> 
> I've run into a problem that has me stumped.  Everything works as long as I
> don't try and copy or assemble a large Assembly file (>80KB).
> 
> I will be going along fine and then out of nowhere I will see CP/M request
> access to Drive "T".  My debug info says SELDSK is requesting Drive 0FF00h.
> 
> I have added debug code to all the CBIOS routines so that they report what
> they are doing to the console (slow but nice).
> 
> I've gone through my code many times and tested each routine via an embedded
> debug monitor.  I believe I have added every CP/M 2.2 patch (1-6 and 9)that
> is specific to the CBIOS including those dealing with Blocking/Deblocking.

What do you mean by "large"?  I've run 2.2 with disks up to 20MB with 
no problems.

CP/M's stack can't be depended upon for much space at all.  Since my 
BIOS code was interrupt driven, every interrupt service routine 
started with a change to a private "system" stack.  I recall having a 
lot of problems before doing that.

Cheers,
Chuck