Stack Depth requirements for CP/M 2.2 CBIOS
robo58 at optonline.net
Fri Jan 30 18:08:49 CST 2009
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.
In the back of my mind I kept wondering if I was exceeding CP/M's Stack
Depth. I can find no information on the web or in my doc's that specifies
what the maximum Stack usage is for a CBIOS.
Do any of you have any thoughts on my Stack Question? Are there other
issues with Blocking/Deblocking that become visible with large Disk Drives,
and that are not covered in any of the published DRI patches?
Thanks for your assistance.
More information about the cctalk