Bad CPU clock problems


Aspera makes very precise use of the CPU clock in controlling the transfer rates. In some systems, this clock is so bad, that it adversely affects the performance. This problem occurs most often in a VM environment, but can also occur on physical systems. Aspera engineering has made a timer test application that can be used to detect bad CPU clocks. It queries the CPU for the tick count every 10 ms, and prints out the maximum divergence above 10 ms, and below 10 ms.


Operating System: Windows, Linux


Download the attached file at the end of this article. The attached Windows file should be renamed from to windows_timer.exe (when unzipped).

The output should look something like this:

D:\Tools\Test Timers\Windows>windows_timer.exe

Aspera Windows timer tester
Press and hold both shift keys to finish:
Results after 5,411 samples:
Max diff: 0.0101167804 seconds ( 33,514 ticks)
Min diff: 0.0092863435 seconds ( 30,763 ticks)
Variance: 0.0008304369 seconds ( 2,751 ticks)
Result: Success


Here is the result from a system with a bad CPU clock:

Aspera Windows timer tester
Press and hold both shift keys to finish:
Results after 8,997 samples:
Max diff: 0.0332441693 seconds ( 118,999 ticks)
Min diff: 0.0032682925 seconds ( 11,699 ticks)
Variance: 0.0299758768 seconds ( 107,300 ticks)
Result: Success


If your clock looks more like the second, or worse, you can expect unpredictable, but poor, performance from your Aspera system. You should really move to a physical system with a good clock. If you already are on a physical system with a bad clock, you should try installing the motherboard manufacturer's latest motherboard drivers (not the BIOS). If that doesn't help, try it on another physical system.



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