Technical Document #73

Technical Document #73
WD_CardRegister() failed to lock a 32MB memory range on my PCI card. The following messages appeared in the Debug Monitor log:
Map_physical_mem_krnl: MmMapIoSpace failed ...
Map_physical_mem_krnl: Try increasing the value of SystemPages ...

The debug log indicates that Windows could not map the relevant memory address range to the kernel-mode virtual address space. As indicated in the log, a possible solution for this is to increase the value of the SystemPages registry entry, in order to increase the number of page table entries in Windows' non-paged pool table. For more information and for other methods for resolving failures to map large memory ranges, refer to Technical Document #59.