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4 – Windows NT Driver Installation
System Registry Parameters
4-4 IS0053301-00 D
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4.6
System Registry Parameters
The following system registry parameters are available with the QLA40xx HBA:
■ MaximumSGList
■ NumberofRequests
■ LargeLuns
4.6.1
MaximumSGList
Windows NT includes enhanced scatter/gather list support for doing large SCSI I/O
transfers. Windows NT supports up to 256 scatter/gather segments of 4096 bytes
each, allowing transfers up to 1,048,576 bytes.
NOTE: The OEMSETUP.INF file automatically updates the registry to support
33 scatter/gather segments. This setting provides the best overall
performance.
To change this value, follow these steps:
1. Click Start, click Run, and open the REGEDT32 program.
2. Select HKEY_LOCAL_MACHINE and follow the tree structure to the QLogic
driver:
HKEY_LOCAL_MACHINE
SYSTEM
CurrentControlSet
Services
Ql4000
Parameters
Device
3. Double-click MaximumSGList:REG_DWORD:0x21.
4. Enter a value from 16 to 255 (10h to FFh). A value of 255 (FFh) enables the
maximum 1-MB transfer size. Any value above 255 enables 64K transfers. The
default value is 33 (21h).
5. Click OK.
6. Exit the REGEDT32 program, then restart the system.
4.6.2
NumberofRequests
Windows NT supports the NumberOfRequests registry parameter to specify the
maximum number of outstanding requests per HBA. When the QLogic driver is