Modify number of Core in a CPU - HowTo Disable cpu core in bios

HP DL585 G7 
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c02715210/c02715210.pdf

AMD Core Select
AMD Core Select uses the BIOS to select the number of software-visible cores per processor.
Compliant operating systems and applications can recognize the reduced core count, which
decreases software-licensing costs.
This can improve performance of applications not written to make use
of the full number of processor cores in the system by giving them access to more cache and
greater memory bandwidth per thread.
The DL585 G7 has a ROM-Based Setup Utility (RBSU) option
(Advanced->Processor Options) that allows two different configurations:
- All cores enabled [default]
- Enable only half of the cores [half disabled] per socket
In a multi-processor configuration, the number of active cores per processor must be equal.  

HP BL495c G5/G6
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=115&prodSeriesId=3782978&prodTypeId=15351&objectID=c01989569

Reboot/startup your HP Proliant Blade server
Press the F9 key on your keyboard during POST (F9 pressed message will how up)
Within the BIOS configuration screen go to the following menu:
Advanced Options > Processor Options > AMD Core Select (Per Node)
Enable or Disable the Processor Cores that are applicable to the system.
Save the new BIOS settings.
Reboot your server and the changes will become active.
See the picture below for more details and understanding:

HP Generic Proliant 300 G6-G7 series with the 4-core Intel Xeon® processor 5500 serie
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01905798/c01905798.pdf
http://h10032.www1.hp.com/ctg/Manual/c00440201.pdf

Generic HP Support Document for:
HP ProLiant BL460c G6 Server series, 
HP ProLiant BL460c G7 Server series, 
HP ProLiant BL490c G6 Server series, 
HP ProLiant BL490c G7 Server series, 
HP ProLiant BL620c G7 Server series, 
HP ProLiant BL680c G7 Server series, 
HP ProLiant DL320 G6 Server series, 
HP ProLiant DL360 G6 Server series, 
HP ProLiant DL360 G7 Server series, 
HP ProLiant DL370 G6 Server series, 
HP ProLiant DL380 G6 Server series, 
HP ProLiant DL380 G7 Server series, 
HP ProLiant DL580 G7 Server series, 
HP ProLiant DL980 G7 Server series, 
HP ProLiant ML330 G6 Server series, 
HP ProLiant ML350 G6 Server series, 
HP ProLiant ML370 G6 Server series

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&objectID=c02786661&jumpid=reg_R1002_USEN

Physical or Logical Processor Cores on ProLiant G6/G7-servers (300-series and above) that are configured with Intel-based processors can be enabled or disabled by a factor of 2. Follow the process outlined in the Details section of this document.