Configure the amount of memory that can be locked for I/O

There is a limit for how much memory the system can lock for I/O (Input/Output) operations. Increasing the limit might benefit applications or drivers, which are highly dependent on highspeed network or harddisk access, as it will allow a larger amount of outstanding I/O.

This DWORD value specifies how much memory (in bytes) that can be locked for I/O operations:

[HKEY_LOCAL_MACHINE \System \CurrentControlSet \Control \Session Manager \Memory Management]
IoPageLockLimit=0 (0 = Calculated at boot, Default = 0)

One can use the following chart for finding a value, though the best value is found by testing: <table border="1"><tr align="center"><th>Total RAM</th><th>IoPageLockLimit (Hex)</th><th>Locked RAM</th><th>Max value</th></tr><tr align="center"><td>64 MByte</td><td>0</td><td>Calculated</td><td>Total RAM minus 7 Byte</td></tr><tr align="center"><td>64-200 MByte</td><td>800000</td><td>2 MByte</td><td>Total RAM minus 16 MByte</td></tr><tr align="center"><td>256-500 MByte</td><td>1000000</td><td>4 MByte</td><td>Total RAM minus 16 MByte</td></tr><tr align="center"><td>512+ MByte</td><td>2000000</td><td>8 MByte</td><td>Total RAM minus 64 MByte</td></tr></table>

Note Windows 2000 RTM (Without any service packs) also reacts to this registry key. If applying a service pack, then this registry setting doesn’t have any affect.

More Info MS KB102985
More Info MS KB121965