HP A6829A PCI Dual Channel Ultra160 SCSI Host Bus Adapter Service and User Guide (May 2003)

Installing the A6829A Adapter
Specifying SCSI Parameters
Chapter 2 29
Maximum Data Transfer Rate
The firmware suggested default for the A6829A adapter’s maximum data
transfer rate is the adapter’s maximum speed (160 MB/s). The A6829A
can communicate with all LVD or SE devices that have speeds up to 160
MB/s. This includes the following speeds (synchronous communication
over a Wide bus):
• Fast (20 MB/s)
• Ultra (40 MB/s)
• Ultra2 (80 MB/s)
• Ultra160 (160 MB/s)
The actual transfer rate between the adapter and a SCSI device depends
on the transfer rate that was negotiated between the adapter and the
SCSI device. However, the actual rate will never be greater than the
maximum data transfer rate set for the adapter.
For example, if you set the A6829A’s maximum data transfer rate to
NOLIMIT (which is same as 160 MB/s, in this case), and then connect a
disk drive that has a maximum data transfer rate of Ultra2 (80 MB/s),
the actual transfer rate will be 80 MB/s.
TIP HP recommends that you always set the A6829A’s maximum data
transfer rate to MAX or NOLIMIT (whichever is applicable to the system),
unless you are trying to debug a communication problem between the
adapter and a specific SCSI device. Using MAX or NOLIMIT allows the
adapter’s maximum transfer rate (160 MB/s) to be used.
You can set the A6829A’s maximum data transfer rate in two ways, as
shown in Table 2-2 on page 24.
To set the maximum data transfer rate for A6829A HBA installed in
PA-RISC based system, see “Setting Maximum Data Transfer Rate for
A6829A Host Bus Adapter Installed in PA-RISC Based System” on
page 30.
To set the maximum data transfer rate for A6829A HBA installed in
Itanium-based system, see “Setting Maximum Data Transfer Rate for
A6829A Host Bus Adapter Installed in Itanium‚-Based System” on
page 34.