I recently got a call from Ian Justman of Sacremento, CA  who  was  having 
trouble  getting NovaDOS to write a second logical extent to a file on his 
S100 system.  He traced the problem to a stack overflow in  NovaDOS.   The 
NovaDOS  stack must serve the stack needs of NovaDOS itself and at least a 
portion of the system BIOS.  While NovaDOS's stack requirement  is  fairly 
consistent,  BIOS's differ in the amount of stack they need.  A BIOS which 
uses a ROM will probably establish it's own stack for low level access.  

I set the size of the NovaDOS stack at 36 bytes in recent releases  up  to 
and  including release I, down from 64 bytes in SuprBDOS and early NovaDOS 
releases.  My Kaypro 10 with an Advent TurboROM uses only about  28  bytes 
of  stack  at the most, but other systems apparently use more.  If you are 
having trouble getting NovaDOS to run, the stack size may be the  culprit.  
Check  the  following  items.   If  1 and 2 are not the source of trouble, 
suspect a stack overflow.


POSSIBLE SOURCES OF PROBLEMS WITH NOVADOS
=========================================

1.  The Reset Disk System Call may be calling a  routine  or  resetting  a 
    flag which is not compatible with NovaDOS operation.  You should leave 
    the resdsk equate set false until you have NovaDOS running.

2.  If the DOS path is supported, the path you have selected may not  have 
    been  properly initialized.  Make sure that the path is initialized to 
    nulls before implementing path support.  Leave pathoff set  to  0  (or 
    ispath equ false) until you have NovaDOS running on your system.

3.  On a few systems, 36 bytes of  stack  space  may  be  insufficient  to 
    handle the stack requirements of both NovaDOS and the BIOS.  If resdsk 
    is set false and the NovaDOS path is disabled and you are still having 
    problems,  increase  the  value  of  the stack size or externalize the 
    stack.  Through release I, the stack size is fixed in NVDS-4.Z80.   Do 
    a  search  in this module for the label p2doss:.  Directly above it is 
    the line "ds 36,0".  If you are  using  an  internal  stack,  you  may 
    increase the 36 to use as much of the free memory reported at assembly 
    time as you need. 

Future releases of NovaDOS will contain an equate in the header file to 
set the internal stack size.

If you have problems or questions, contact me.

Lindsay Haisley
14206 Speading Oaks Drive
Leander, TX  78641

(512) 259-1190 vox
(512) 444-8691 data (Z-node 77)