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Beginner
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Calculate the Max Flops on Skylake

 

I calculate the Max Flops on Skylake with cpu- frequency*16.

Is cpu-frequency*32 on GOLD version of Skylake? 

 

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Beginner
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CPU processor Max Turbo Frequency is 3.8GHz, but AVX-512 Max Turbo Frequency is only 2.3GHz. Why is this?

And calculate Max GFLOPS always use ( CPU-Base-Frequency * cores * 32(or 16, 8, 4) ) before.

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Beginner
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Are there any relations between AVX-512 Frequency and CPU Processor Frequency?

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Black Belt
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The nomenclature can be confusing.  The "non-AVX" frequencies, the "AVX 2.0" frequencies, and the "AVX-512" frequencies are all CPU core frequencies, with the different tables applying to code with different SIMD register widths in use.

For any CPU model, the maximum frequency that each core can run at is determined by both the number of active cores and by the width of the SIMD units that are active in each core.   In figure 3 above, the label "AVX-512 Turbo Frequencies" means the maximum frequency that any core can run at when the 512-bit SIMD units are active.  (The 512-bit SIMD units are active whenever the processor has executed an instruction using 512-bit registers in the last millisecond.)

As an example, we can compare the values in Figures 1, 2, 3 from the "Intel Xeon Processor Family Specification Update" (document 336065-005, February 2018) for the Xeon Platinum 8180.   If there are 20 active cores:

  • any of the cores with the 512-bit SIMD units active can run at up to 2.6 GHz (Figure 3, row 1, column for 20 cores active)
  • any of the cores with the 256-bit SIMD units active can run at up to 3.1 GHz (Figure 2, row 1, column for 20 cores active)
  • any of the cores with neither 256-bit nor 512-bit SIMD units active can run at up to 3.5 GHz (Figure 1, row 1, column for 20 cores active)

These tables provide the maximum turbo frequencies for each case -- the actual frequencies will be reduced if needed to keep the running average power under the TDP limit for the processor model. 

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Hi McCalpin, your comments is really very helpful. But I still have a question and I didn't find out the answer from Google or Intel Official web site.

1.We usually calculate CPU performance by Frequency*IPC*Cores. But Intel does not seem to release IPC of each CPU. So my first question is how to get IPC of each CPU.

2.According to your comments above, it seems we can not use the processor basic frequency released by Intel on the official site. Is there a formula which can calculate the CPU performance using the Processor Basic Frequency ?

Frequency.png

Thank you very much.

McCalpin, John (Blackbelt) wrote:

The nomenclature can be confusing.  The "non-AVX" frequencies, the "AVX 2.0" frequencies, and the "AVX-512" frequencies are all CPU core frequencies, with the different tables applying to code with different SIMD register widths in use.

For any CPU model, the maximum frequency that each core can run at is determined by both the number of active cores and by the width of the SIMD units that are active in each core.   In figure 3 above, the label "AVX-512 Turbo Frequencies" means the maximum frequency that any core can run at when the 512-bit SIMD units are active.  (The 512-bit SIMD units are active whenever the processor has executed an instruction using 512-bit registers in the last millisecond.)

As an example, we can compare the values in Figures 1, 2, 3 from the "Intel Xeon Processor Family Specification Update" (document 336065-005, February 2018) for the Xeon Platinum 8180.   If there are 20 active cores:

any of the cores with the 512-bit SIMD units active can run at up to 2.6 GHz (Figure 3, row 1, column for 20 cores active)

any of the cores with the 256-bit SIMD units active can run at up to 3.1 GHz (Figure 2, row 1, column for 20 cores active)

any of the cores with neither 256-bit nor 512-bit SIMD units active can run at up to 3.5 GHz (Figure 1, row 1, column for 20 cores active)

These tables provide the maximum turbo frequencies for each case -- the actual frequencies will be reduced if needed to keep the running average power under the TDP limit for the processor model. 

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Black Belt
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(1) The information you need on max operations per cycle is not easy to find, but all the available information is contained in the posts above.

(2) There is no formula to determine the maximum all-core Turbo frequency from the "nominal" frequency.  You have to look up the model-specific information in the "Specification Update" document for the processor family you are interested in.

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Beginner
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Thank you very much. I have already got the information you mentioned.

McCalpin, John (Blackbelt) wrote:

(1) The information you need on max operations per cycle is not easy to find, but all the available information is contained in the posts above.

(2) There is no formula to determine the maximum all-core Turbo frequency from the "nominal" frequency.  You have to look up the model-specific information in the "Specification Update" document for the processor family you are interested in.

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