Out of System PTEs on a Computer w/ More Than 768 MB of Memory

• Microsoft Windows NT Operating System version 3.1
• Microsoft Windows NT Advanced Server version 3.1
• Microsoft Windows NT Workstation versions 3.5 and 3.51
• Microsoft Windows NT Server versions 3.5 and 3.51

SYMPTOMS

Your total system paged table entries (PTEs) may not scale up as you add more memory. In fact, you may have fewer system PTEs available after exceeding 768 MB of memory.

CAUSE

Computers with more than 768 MB of physical memory have fewer available system PTEs than computers with less memory. Increasing the memory capacity of a computer from 512 MB to 1 GB, for example, means you can now run fewer threads. The algorithm for Microsoft Windows NT version 3.51 trades off non-paged pool and system PTE space. Once the sum of these two regions exceeds the allowable space, the number of system PTEs is reduced. On a DEC Alpha computer, this occurs around 768 MB of physical memory.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Windows NT versions 3.1, 3.5, and 3.51. This problem has been corrected in Microsoft Windows NT version 4.0.