HT Processor Logical Core Numbering in Windows 7 & Windows XP Task Managers

I am running a dual boot system with Window 7 & Windows XP on my ASUS G73Jh with an OEM Core i7-920XM. I am unable to turn off the HT in the BIOS of my machine, so am using CoreAffinityResident in XP to automatically set the processor affinities for my Engineering software (Matlab, TI Code Composer Studio IDE & Xilinx ISE).

I think that in Windows 7 Task Manager the virtual HT cores are the odd numbered cores (i.e. 1,3,5,7 for a Quad Core CPU), and the other cores are the physical cores (0,2,4,6). However I think that in Windows XP Task Manager the physical cores come first (0,1,2,3), followed by the virtual HT cores (4,5,6,7).

Please can someone let me know if I am correct in my assumptions.

 

No clue about the task manager. I was under the impression that they were the same order in any OS, "real" cores on 0,2,4, etc. and HT cores on 1,3,5, and so on.

 

Thanks. I was also under the same impression, but testing with Prime 95 seems to indicate that the cores are numbered differently in XP, although I could be wrong.

All the XP Hyperthreading reviews which I have read only talk about the Pentium 4 HT processors, so there is only one physical and one virtual CPU in the Task Manager.

It is a pity that I can not turn the HT off in the BIOS like in the Clevo W870CU, since all my development tools currently run under XP, and I can not afford to upgrade to the latest versions.

 

Why do you want to turn HT off? From what I've read about the new implementation, they've fixed the performance decreases that some apps got on the P4-era hyperthreading, so hyperthreading is never a problem any more, only a performance benefit.

 

I am not too sure about how HT aware Windows 7 is, since it sometimes schedules heavily loaded threads on the same core to avoid the turbo boost speed drop that occurs when multiple cores are active. The 920XM and 940XM processors do not suffer from this artificial slowdown, and can be configured to run at fast as possible, within the thermal and power limits of the system.

Anyway, most of my Engineering software runs under Windows XP and does not work under Windows 7 (or XP Mode), since I am using external hardware. The latest versions cost money, and are still not fully Windows 7 compatible, so it is best for me to continue using Windows XP for development work, and to use Window 7 for gaming.

Since XP does not seem to be fully HT aware, I need to turn off the Hyperthreading or set the processor affinities manually, to avoid heavily loaded threads being run on the same core.