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Originally Posted by valis  BUT, my understanding was also that in the cpu C1E and EIST are using the same EIST circuit (for P-states) via IA32_PERF_CTL. So when I disable EIST in my Bios I see all C-states unselectable as well, and so assumed that this register was disabled removing support for both. I do understand though that some cpu's (or chipsets?) can support EIST but not C1E, or C1E but not EIST (though I think with C1E only, just a portion of EIST logic is enabled - it will only do the maximum and minimum P-state.).
I think the confusion is just that I haven't seen a bios support both where turning EIST off didn't disable both (perhaps because I run Supermicro/Intel hardware and not consumer/overclocker?) so I assumed the mechanism was the same for both in the hardware implementation. I've not been intimate with the x86 architecture on that low of a level in a few decades tough so I am not surprised if my understanding is flawed. |
Hey Valis,
When disabling EIST in the BIOS on your SM board, is it actually disabling the C-states or simply not giving you the option to adjust the states. It will be interesting to see whether the C-States are still active- C1E would be the main focus.
Easy enough to check , set C1E on in BIOS, then disable the EIST and then check the clocking with
CPU-Z , which communicates directly to the chip via CPUID. If the C1E states is still active it will report the CPU clocking down , even with EIST disabled
Windows simply reports the CPU's at full clock , when in fact they are being ramped down.
On the current single socket boards, C States and EIST are total separate in the BIOS, you can disable them individually without effecting the others.
If you disable EIST without disabling C1E and the other C States the hardware clocking control is still active. Turbo Boost is another variable as well, but that only clocks the CPU up, not down.
FWIW: The Tyan 5400 boards that were the same series as your system had access to C states, but didn't have an option to disable EIST , so every BIOS will be different. Same on single socket boards, except it was the opposite ,some have access only to EIST, not to C-States.
From what I have experienced its imperative to disable the C states on a workstation where possible. Some anomalies unrelated to clocking that I experience on my current X58 development system with the C states active range from high pitched whining from the VRM's to earthing artefacts in professional PCI/PCIe audio cards , to even stranger occurrences in OSX with mouse / GUI causing the VRM/earthing issues.
Disabling the C Halt and EIST and it all goes away.
The power management states and their associated anomalies are a constant enigma to me at times.
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This I agree with as well, higher temps would only be in situations where you're not under full load all the time. Another way of saying it though is that by disabling all power management of the cpu you're running everything full throttle all the time. Not a bad thing for audio for sure but for those who don't actively manage their own machines and/or build them I worry about cooling issues, especially with lower tier vendors. Ie, home & project studio users who might attempt to tweak things thinking they'll buy more performance.
Also it makes the assumption that all audio users are running 100% usage anyway. While that's certainly probably true for very productive studios and people who are capable of managing their own hardware, again I am not sure about the home/project users (I know that I for instance rarely see more than 50-60% usage of either of my 2008 Xeons unless I'm doing visualation work, 3d rendering or gaming.)
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Sorry I didn't explain that too well, what I meant by flat out was only in reference to the clock speed being flat out , so at low to moderate load there would be a temp advantage , but not once the CPU clocks to full speed.
With the Cooling, system burn ins at build/development should be at 100% load for long periods to ensure the system will be capable of handling extreme work loads, so on 50-60% working environments, there is still plenty in the tank.
Of course that would be valid for professional workstations, but I doubt that would be a priority for more domestic usage, and thats were some users could get themselves into a trouble with cheaper alternatives.
