ZEOS 486/50 with More Than 16 MB RAM May Generate Kernel Trap

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1

SYMPTOMS

ZEOS 486/50 machines with greater than 16 megabytes (MB) of RAM may cause a STOP message to appear (kernel trap) if the SRAM option is enabled in the system CMOS.

CAUSE

The ZEOS 486/50 has an optional SRAM cache that may be enabled.

RESOLUTION

To correct this problem, either disable the SRAM Cache option in the CMOS settings if more than 16 MB of RAM is to be installed, or install 16 MB or less of physical RAM and enable the SRAM Cache option.

MORE INFORMATION

For more information regarding machines with memory greater than 16 MB, refer to the README.WRI file in the \<wnt root>\winnt\system32 directory.

The following is an excerpt from README.WRI:

When accessing memory above 16 MB, Windows NT Virtual Direct Memory Access compensates for the limitations inherent in the 24-bit DMA hardware used by 16-bit ISA bus PCs using a technique called double buffering.

Double buffering usually provides performance that is within a few percent of 32-bit hardware DMA used with 32-bit bus architectures (such as EISA, MCA, etc). In general, Windows NT will continue to take full advantage of additional RAM in PCs with ISA, EISA, MCA, and other 32-bit bus architectures up to a maximum of 4 GB.

A few ISA-based PCs have unusually poor hardware secondary cache schemes. On these machines, increasing memory beyond 16 MB will actually degrade, rather than improve, performance. This is a hardware limitation of these particular machines and is not specific to Windows NT.