Windows XP Driver Installation

This section describes theSYMMPI.SYS driver for the Windows XP operating system. It provides instructions for existing system installations and includes these topics:

• Section 7.5.1, “Installing the SYMMPI.SYS Driver”

• Section 7.5.2, “Performance Tuning”

This driver supports only Windows XP.

7.4.1 Installing the SYMMPI.SYS Driver

The following procedures install theSYMMPI.SYS driver onto a new or existing Windows XP system.

7.4.1.1 New System Installation

This procedure installs theSYMMPI.SYSdriver onto a new Windows XP system. Windows XP automatically adds the driver to the registry and copies the driver to the appropriate directory.

These instructions assume the use of a CD-ROM. The system BIOS must support booting from a CD-ROM. BIOS settings might require changes to allow CD-ROM booting. Refer to your system documentation.

Step 1. Start the Windows XP installation by booting from the Windows XP CD-ROM.

The system BIOS must support booting from a CD-ROM. BIOS settings might require changes to allow CD-ROM booting. Refer to your system’s documentation.

Step 2. Press F6 to install theSYMMPI.SYS driver when the screen displays:

“Press F6 if you need to install...”

Note: You must press F6 for the system to recognize the new driver. Otherwise, the system does not recognize the devices controlled by the driver during the Windows setup.

Step 3. Choose S to specify an additional device when the screen displays:

“Setup could not determine the type...”

Note: If this screen is not displayed as the first user input, then the F6 key press was not seen by the setup program.

Reboot the system and return to Step 2.

The system prompts for the manufacturer-supplied hardware support disk.

Step 4. Insert the Window XP driver diskette and press Enter.

Step 5. Select the appropriate Windows XP driver from the menu by highlighting it and press Enter to proceed.

Step 6. Follow the Windows XP installation procedure from this point.

7.4.1.2 Existing System Installation

This procedure installs or upgrades theSYMMPI.SYS driver onto an existing Window XP system.

Step 1. Boot Windows XP.

The Found New Hardware Wizard appears. The information on the first page of this window identifies the SCSI controller and requests the driver diskette.

Step 2. Insert the Windows XP driver diskette into the floppy drive.

Step 3. Choose the Install Software Automatically option.

Step 4. Click on the Next button.

Step 5. In some cases, a message displays saying that this driver is not digitally signed. This message informs you that a nonsigned driver is being installed. Click on Continue Anyway.

Step 6. The system loads the driver from the Windows XP driver diskette and copies the driver to the system disk.

The Found New Hardware Wizard screen appears and displays the message:

“The wizard has finished...”

Step 7. Click on the Finish button to complete the driver upgrade.

7.4.2 Performance Tuning for Windows XP

Windows XP offers registry entries that can tune the performance of SCSI I/O for certain configurations. The tunable parameters are the large transfer block size support and the guaranteed number of concurrent I/Os for a particular SCSI bus.

7.4.2.1 Large Block Size Support

TheSYMMPI.SYSdrivers can support up to a 1 Mbyte transfer size in Windows XP; however, the default Windows XP transfer size is

64 Kbytes. To enable better performance, the driver installation process adds a registry entry to enable 256 Kbytes transfer sizes. Programmers can also use thempi_256K.regfile to set or re-enable the maximum transfer size. There are two methods to add this registry setting. The first method is to locate the mpi_256K.regdata file using

Windows Explorer, double-click on the file, and edit it. The second method is to type at the command prompt:

regedit mpi_256K.reg

This command inserts an entry in the registry to enable 256 Kbytes block size support.

Editing the mpi_256K.regcan set any maximum block size between 64 Kbytes and 1 Mbyte. The formula to calculate the proper value for MaximumSGList in a 32-bit OS is:

MaximumSGList = [(Maximum Block Size)/4 Kbytes] + 1

For 64-bit systems, the OS page size is 8 Kbytes instead of 4 Kbytes.

Therefore, the maximum transfer size is 2 Mbytes, the default driver installation enables support for 512 Kbytes transfer size, and the formula to calculate the MaximumSGList is:

MaximumSGList = ((Maximum Block Size)/8 Kbytes) + 1

As an example, to determine the MaximumSGList value for 256 Kbytes in a 32-bit OS, take [(256 Kbytes/4 Kbytes) +1] = 65 (or 0x41 in hexadecimal).

The maximum value allowed for MaximumSGList is 255 or 0xFF. For the particular value of 0xFF, the internal value passed to Windows XP is

Read the information in thempi_256K.regdata file before editing it.

The system must reboot for the new registry setting to be effective. To reset the maximum block size to the default of 64 Kbytes, follow the instructions above, except use mpidfblk.reg as the data file.

7.4.2.2 Maximum Number of Concurrent I/Os (Guaranteed)

Windows XP guarantees a maximum of 32 concurrently active I/Os on a particular SCSI bus. Due to the method of memory allocation, the actual limit of concurrent I/Os can vary between various drivers or versions of drivers. This can have a significant impact on performance benchmarking between different driver versions or adapter vendors. In effect, one adapter could support 80 outstanding I/Os, while another adapter could only support 32 outstanding I/Os.

To enable better performance, the driver installation process adds a registry entry to support 128 concurrent I/Os. If a different maximum value is desired, programmers can use the mpi100io.regdata file to add a registry entry that set the maximum numbers of concurrent I/Os. There are two methods to add this registry setting. One method is to locate the mpi100io.regdata file using Windows Explorer, double-click on the file, and edit it. The other method is to type at the command prompt:

regedit mpi100io.reg

This command inserts an entry in the registry to guarantee a maximum of 100 concurrent I/Os per adapter.

Note: Setting this value to a high number uses increasing amounts of nonpaged pool memory, which is a critical Windows XP resource. High values for this setting can degrade system performance.

Be sure to read the information in thempi100io.reg data file before editing it. You must reboot system for the new registry setting to take effect. To reset the guaranteed number of concurrent I/Os to the Windows XP default of 32, follow the instructions above but use mpidefio.regas the data file.