Enabling and Disabling Hyper-Threading on Dual-Core Intel® Itanium® 2 Processors

nPartitions with dual-core Intel® Itanium® 2 processors support Hyper-Threading. Hyper-Threading provides the ability for processors to create a second logical CPU on a single core that can allow additional efficiencies of processing. For example, a dual-core processor with Hyper-Threading active provides four logical processors, two on each processor core.




	CAUTION: Some operating systems do not support Hyper-Threading. Problems can occur when running an OS that does not support Hyper-Threading on an nPartition that has Hyper-Threading enabled.




	NOTE: You must reset an nPartition when changing its Hyper-Threading status. Hyper-Threading will not be enabled or disabled until after the nPartition is reset.

Checking the Hyper-Threading Status for an nPartition. To check the current Hyper-Threading status for an nPartition:

From the EFI Shell: cpuconfig or cpuconfig threads
From HP-UX: setboot
Using the Enhanced nPartition Commands: parstatus -T

Example 7-2 Checking the Hyper-Threading Status for an nPartition

# setboot
Primary bootpath : 0/0/1/1/0.12.0
HA Alternate bootpath : 0/0/0/1/0
Alternate bootpath : 0/0/0/1/1

Autoboot is ON (enabled)
Hyperthreading : ON 1
               : OFF (next boot) 2
#

1	The HP-UX setboot command indicates that Hyper-Threading currently is enabled (`ON`) for the nPartition.
2	The next time the nPartition is booted (after it is reset), Hyper-Threading will be disabled (`OFF`) for the nPartition.

Enabling Hyper-Threading for an nPartition. To enable Hyper-Threading, use any of the following methods and then reset the nPartition whose Hyper-Threading status you have changed:

From the EFI Shell: cpuconfig threads on
From HP-UX: setboot -m on
Using the Enhanced nPartition Commands: parmodify -pn -T y, where n is the nPartition number.
Using Partition Manager: Perform the Modify nPartition task and select the Enable Hyper-Threading check box on the Configure Memory tab.

You must reset an nPartition after changing its Hyper-Threading status.

Example 7-3 Enabling Hyper-Threading for an nPartition

Shell> cpuconfig threads 1
cpuconfig: Threads are turned off.

Shell> 
Shell> cpuconfig threads on 2
cpuconfig: Threads will be on after a reset.

Shell>

1	The EFI Shell cpuconfig threads command indicates that Hyper-Threading currently is disabled (`turned off`) for the nPartition.
2	This EFI Shell command configures Hyper-Threading to be enable after the nPartition is reset.

Disabling Hyper-Threading for an nPartition. To disable Hyper-Threading, use any of the following methods and then reset the nPartition whose Hyper-Threading status you have changed:

From the EFI Shell: cpuconfig threads off
From HP-UX: setboot -m off
Using the Enhanced nPartition Commands: parmodify -pn -T n, where n is the nPartition number.
Using Partition Manager: Perform the Modify nPartition task and deselect the Enable Hyper-Threading check box on the Configure Memory tab.

You must reset an nPartition after changing its Hyper-Threading status.

Enabling and Disabling Hyper-Threading on Dual-Core Intel® Itanium® 2 Processors

Technical documentation

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