Enabling 64 bit mode

[summa1234]

Hi,
I am running Windows XP 64 on a machine with a Nocona processor.

1) Do I have to enable the 64 bit mode by writing to some register or is the 64 bit mode on by default? In other words, are there any tricks to get the maximum/best performance?

2) When I run perfsys on a Windows 2K with the same processor one of the FFTs reported 6.2 GFLOPS while the same reported 8.7 GFLOPS on the XP 64. Are these numbers realistic or can I do better?

3) Perfsys always reports using ippst7.dll (whether running Win 2K or XP 64). However the manuals suggest that the processor ID for Nocona would be m7. Am I missing something here?

Any response to the above questions is highly appreciated.
Rgds,

[Vladimir_Dudnik]

Hi,

1) You do not need in any manual setting to enable 64-bit mode for processors with support of EM64T. It is operating system responsibility.

2) Windows2000 do not support 64-bit mode, so in this case processor works in 32-bit mode and IPP uses T7 libraries. Windows XP 64-bit does support 64-bit mode, so IPP will use M7 libraries, and some functions will work faster, as in your case with FFT.

3) If you use perfsys.exe which was build for 32-bit mode (you take it from ia32_itanium folder) it only knows about 32-bit processors and will report and use T7 library on your EM64T system. You need to use perfsys.exe from em64t folder (if you did install IPP for EM64T).

Hope it helps,

Vladimir