Compatibility: 2.0+
Purpose: Allocates additional stack space for DOS.  If you see the
message...
Internal Stack Failure
System Halted
...then you should put a STACKS= statement in CONFIG.SYS

Syntax: STACKS= n,s

  Parameters  

n is the number of stacks to allocate (0-64; default=9)

s is the size (in bytes) of each stack (32-512; default=128)

  TECH Notes  

  DOS typically intercepts interrupts 02H, 08H-0eH, 72H-74H, and 76H-77H
(see Interrupts and BIOS Services) which handle IRQs.

When one of these interrupts occurs, DOS points SS:SP to an internal
data area; that is, it switches stacks.  This is supposed to minimize
the chance of a hardware interrupt overflowing an application's stack.

Note: DOS only performs stack switching when n is greater than 8.

  STACKS=0,0 saves about 1K of conventional  memory (but it may cause
problems when running communications software or other interrupt-
intensive applications, or when running poorly-written software that
supplies insufficient internal stack space for handling external
interrupts.

  A worst-case scenario -- such as an interrupt interrupting an
interrupt, which itself is interrupted (etc.) -- can cause a stack
overflow.  If that happens, you should fall back to the default stack
settings or even increase them.

- -

STACKS= (CONFIG.SYS Command)