OAL Memory Mapping Structures (Compact 7)

3/12/2014

Windows Embedded Compact 7 improved Windows CE’s physical memory management design for ARM and x86 to allow you to address more than 512 MB of memory. These changes do not apply to MIPS and SHx. In order to support more than 512 MB of RAM, the way OEMAddressTable is used has been changed, and OEMDeviceTable and Ramtable have been introduced.

• OEMAddressTable
  This table should now only define address mappings required for system startup, and should only be mapped to cached memory. The format of entries in this table has not changed.

• OEMDeviceTable
  This table contains all the device mappings that used to be in OEMAddressTable. There is only one mapping created for each entry in this table, and that mapping will use the cache attribute specified in the entry. No longer will both cached and uncached mappings be made to the same physical address.

• RamTable
  Any RAM beyond the 512 MB that is defined in OEMAddressTable, is defined in this table. You are not required to use OEMRamTable with platforms that use 512 MB of RAM or less, but we recommend that you use it to be compatible with future CPUs that don’t allow conflicting memory attributes (such as cached and uncached) be applied to the same physical address.For more information on using the new memory management system, and how to disable uncached static mapping to make more virtual memory space available for the kernel, see Modify OEMAddressTable and KITL Drivers.

The following list contains the OAL structures used to map physical memory.

In This Section

• OEMAddressTable
  Defines physical-to-virtual address mappings required for system startup.

• OEMDeviceTable
  Defines virtual-to-physical address mappings for uncached devices on the x86 and ARM platforms.

• OEMRamTable
  Defines the RAM available in addition to the RAM defined in OEMAddressTable.

• OEMRomChain
  Stores information about an Execute-in-place (XIP) region.

Remarks

See Also

Reference

OAL Structures