Disable C-States on i7 for fps boost
#11
Disabling C-State tech has the side affect of reducing your overal memory bandwidth.

http://forums.aida64.com/index.php?/topi...dth-tests/

Anyway, the problem is actually Turbo related, disabling C-state just disables the second turbo state.
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#12
(07-24-2011, 09:28 PM)Rezard Wrote: A bit on what C-States do...
  • C0 – Active: CPU is on. C0 is the operating state.
  • C1 – Auto Halt: core clock is off. C1 is a state where the processor is not executing instructions, but can return to an executing state essentially instantaneously. Some processors also support an Enhanced C1 state (C1E) for lower power consumption.
  • C2 – Stop Clock: core and bus clocks are off. C2 is a state where the processor maintains all software-visible state, but may take longer to wake up.
  • C3 – Deep Sleep: clock generator is off. C3 is a state where the processor does not need to keep its cache coherent, but maintains other states. Some processors have variations on the C3 state (Deep Sleep, Deeper Sleep, etc.) that differ in how long it takes to wake the processor.
  • C4 – Deeper Sleep: reduced VCC

Does any of this sound like it could reduce performance?

you are right concerning the basic function states. to get on your question. C1 is latency immune. C2+ states are determined with a number the cpu can read of the ACPI I/O table. therefore C2 and deeper states do always consume time, however as long as the timing uses one and the same basic freq, the latency don't leave any noticeable affect. in other words C2 is almost latency immune. things will change with C3+ states then the RTC got to emulate the system clock. this timing is calculated with high precition but neverless not real more likely a logic link. because of it frequently broadcasting is necessary to handle the ACPI timing. new extra latency are result of this broadcast mechanism. actually the performance is platform specific. the manufactor decite the ratio between powersave/performance by means of the platform basic setup. extra added functions are usually provided for users who prefer their own favorite setup.

The new i7 core platforms got new hardware supported mechanism to handle these timings. it function is similiar to the ACPI software emulation. first performance problems with specific software are already public and labeled as 'skew effect'. its recommanded to set the max. C state on C2 once watching those behavior.
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