Error Message: There Are No Spare Stack Pages

• Microsoft Windows 95

SYMPTOMS

When you are running Windows 95, you may receive the following error message:

   There are no spare stack pages. It may be necessary to increase
   the setting of 'MinSPs' in System.ini to prevent possible stack
   faults. There are currently <nnn> SPs allocated.

CAUSE

This error can occur when Windows 95 encounters an internal overflow of the stacks used by 32-bit Windows device drivers. Please note that this is not related to the "Stacks=" line in the Config.sys file, which is used for 16-bit MS-DOS device drivers.

Stack overflow conditions are indicative of errors in the device driver. Device drivers are allocated 4 kilobytes (one page) of space to be used as a stack. If the device driver uses more than 4 kilobytes of memory, a stack overflow condition occurs.

Windows 95 sets aside a number of extra memory pages (spare stack pages) to be used temporarily to prevent a system "crash" due to a stack overflow condition. When the stack overflow condition has passed, Windows 95 reclaims the temporary page. The default number of spare stack pages is 2.

If Windows 95 detects that it has run out of spare stack pages, the warning message stated above is displayed. Windows 95 continues to operate normally unless a device driver encounters a stack overflow condition when there are no free spare stack pages.

RESOLUTION

To resolve this situation, add the following line to the [386Enh] section of the System.ini file and then restart your computer:

   MinSPs=4

NOTE: Each spare stack page requires 4 kilobytes of memory.