Wyatt's World

Cracking Open The Pentium III

Is there any new performance/profiling information?

The performance registers within the Pentium III are identical to the performance registers within the Pentium II, apart from the addition of the following:

Event Num.	Unit Mask	Description
SIMD Instruction Performance Counters
0xD8	0x00	Packed and Scalar SIMD Instructions retired
0xD8	0x01	Scalar SIMD Instructions retired
0xD9	0x00	Packed and Scalar SIMD computational instructions retired
0xD9	0x01	Scalar SIMD computational instructions retired
Prefetch Performance Counters
0x07	0x00	Non temporal prefetch instructions dispatched, including speculative.
0x07	0x01	Prefetch instructions dispatched for all caches, including speculative.
0x07	0x02	Prefetch instructions dispatched for L1 and L2, including speculative.
0x07	0x03	Weakly ordered stores dispatched, including speculative.
0x4B	0x00	Non temporal prefetch instructions that missed all caches
0x4B	0x01	Prefetch instructions that missed all caches
0x4B	0x02	Prefetch instructions for L1 or L2 that missed all caches
0x4B	0x03	Weakly ordered stores that missed all caches

Accessing and using the performance information is beyond the scope of this article. (I covered the subject in depth in my article "Building an Inline Performance Monitoring System", Game Developer, May 1998). With this article and the information above, you should have no problem reading the new events. VTune 4.0 also has the ability to read the new Pentium III performance counters, if you don’t want to do it yourself.

For Further Information

Lots of information can be found on Intel’s developer web site. This site contains lots of source code examples, all the processor manuals, and the SIMD tools mentioned within this article. If you have VTune 4.0, you’ll find all of the SIMD example code and the latest processor manuals (including the optimization manual) on the CD-ROM. Check out the following:

http://developer.intel.com/design/pentiumiii/manuals (Pentium III manuals)
http://developer.intel.com/vtune/cbts/strmsimd/appnotes.htm (PentiumI III App Notes)
http://developer.intel.com/design/pentiumiii/applnots/245125.htm (Serial Number)
http://developer.intel.com/design/pentiumii/applnots/241618.htm (CPUID)
http://developer.intel.com/design/pentiumiii/psover.htm (Serial Number Control)
http://developer.intel.com/vtune/macropak/index.htm (MASM macro file)
http://developer.intel.com/vtune/rvt/index.htm (Register viewing tool)
http://developer.intel.com/vtune/optidrvr/index.htm (NT4.0 SIMD driver)
http://developer.intel.com/vtune/ (VTune home page)

Next month I’ll explore processor detection, using a DLL that detects every feature of every make and model processor on the market. If you have a question about this article, Pentium processors, Windows or PCs in general, then email them to me at Gamasutra@Rob-Wyatt.com

Rob has been involved with games and system level code on almost every major platform for the past 12 years. Currently he is mainly involved with PCs and Windows. When he is not working, he can be found either flying his Cessna out of Santa Monica airport or at the pub. He can be contacted at Gamasutra@Rob-Wyatt.com.

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