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Puzzle 29
What Do You Do When It Mega Hurts? |
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QuickHow many processors are on the system where your application is running? How fast is the CPU? What do you do when Intel announces a problem with a particular run of processors and you need to determine the exact type, model, and stepping number of the CPU running your application? |
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Intel provides a DLL that lets you obtain all this information. It's called cpuinf32.dll and can be found on their Web site at http://developer.intel.com/vtune/cpuid/package.htm, where you will also find instructions for downloading the package.1 |
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Now, before you get too excited about this cool little DLL, I must warn you that it works reliably only with Intel processors. Nevertheless, it poses a fascinating problem. |
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The DLL includes a function called cpuspeed, which can be used to determine the raw and normalized speeds of the CPU.2 The C declaration of the function is as follows: |
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struct FREQ_INFO cpuspeed(int clocks); |
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The clocks parameter should be set to 0 to use the default number of clock cycles for testing. The FREQ_INFO structure is defined as follows: |
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Type FREQ_INFO
in_cycles As Long ' Internal clock cycles during test
ex_ticks As Long ' Microseconds elapsed during test
raw_freq As Long ' Raw frequency of CPU in MHz
norm_freq As Long ' Normalized frequency of CPU in MHz
End Type |
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Care to try to come up with the correct declaration for this one? |
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1 At least, it's there at the time of publication. If it moves, you'll find the updated location at http://www.desaware.comonce we find it. |
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2 The normalized frequency is supposedly the nearest standard CPU frequency to the measured frequency. In practice, the number just seems to be the speed adjusted for rounding errors. |
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