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C – Troubleshooting
BIOS Settings
C-4 IB6054601-00 D
Q
C.2.3
Incorrect MTRR Mapping Causes Unexpected Low Bandwidth
This same MTRR Mapping setting as described in the previous section can also
cause unexpected low bandwidth if it is set incorrectly.
The setting should look like this:
MTRR Mapping [Discrete]
The MTRR Mapping needs to be set to Discrete if there is 4GB or more memory in
the system; it affects where the PCI, PCIe, and HyperTransport i/o addresses
(BARs) are mapped. If there is 4GB or more memory in the system, and this is not
set to Discrete, you will get very low bandwidth (under 250 MB/sec) on anything
that would normally run near full bandwidth. The exact symptoms can vary with
BIOS, amount of memory, etc., but typically there will be no errors or warnings.
To check your bandwidth try:
$ ipath_pkt_test -B
When configured correctly, PICIe InfiniPath will normally report in the range of
1150-1500 MB/s, while HTX InfiniPath cards will normally report in the range of
2300-2650 MB/s. ipath_checkout can also be used to check bandwidth.
You can check and adjust the BIOS settings using the BIOS Setup Utility. Check
the hardware documentation that came with your system for more information on
how to do this.
C.2.4
Change Setting for Mapping Memory
In some cases, on systems with 4GB or more memory on Opteron systems with
InfiniPath HTX cards (QHT7040 or QHT7140), and the Red Hat Enterprise Linux 4
release with 2.6.9 Linux kernels, MPI jobs may fail to initialize or may terminate
early. This can be worked around by changing the setting for mapping memory
around the PCI configuration space ("SoftWare Memory Hole") to "Disabled" in the
Chipset, Northbridge screen in the BIOS. This will result in a small loss in usable
memory.
C.2.5
Issue with SuperMicro H8DCE-HTe and QHT7040
The InfiniPath card may not be recognized on startup when using the SuperMicro
H8DCE-HT-e and the QHT7040 adapter. To fix this problem, the OS selector option
in the BIOS should be set for Linux. The option will look like this:
OS Installation [Linux]