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Originally Posted by TAFKAT  EIST /Speed stepping is dynamically controlled via software i.e the O.S , power consumption /heat is reduced by clocking the CPU down at lower usage , C Halt states are processor level modes thats are designed to reduce power consumption by halting specific sections of the CPU when not in use , which may or may not reduce clock frequency. They are directly related to the ACPI.
Although EIST and C Halt seem to do similar things, they are totally different processes. |
Ok I see where we're confused I think.
Ok so I do understand the difference between hardware controlled C1/C1E and OS controlled EIST via ACPI. And my understanding is that "technically" EIST is for managing processor P-states (voltage) in the C0 state only (correct? voltage control for power consumption reduction in lower processor states than fully active?) And so C1 (halt) is independant of power, at least until C1E also brought the ability to execute HLT and put the core into it's lowest halt state along with a transition of that core into lowest P-state (voltage & multiplier/frequency drop.)
And I understand what you're saying about Speedstepping (and Enhanced EIST) being a mechanism invoked from the OS via ACPI versus the C1 states (which are not as finely grained either I think?)
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.
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Originally Posted by TAFKAT But the higher temps would only be at idle to moderate , when running flat out there should not be any more heat generated as EIST/C Halt would/should not be in play. This is on Windows, all bets are off with OSX, as OSX cannot arbitrate EIST, and who knows whats actually happening with the C States with the MACPro EFI.
Re Harpertown v Nehalem Dual Socket Systems , the prior generated enormous heat via the FB DIMMs / Northbridge as you noted, while the Nehalems run a little hotter but the memory runs way, way cooler . I have always used 3rd party heatpipe coolers on my Dual Xeons Systems , I wouldn't trust the Intel units as far as I could throw them.. :-) |
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.)
As for the 2009 Mac Pro, I can only draw from what I've read from people online seeing warmer temps. Though I haven't heard of that causing failures I just worry about 50-60C temps inside my machine, let alone the issues where the new Nehelems are showing 80-90C errata.
And yes, I fully agree that my MCH & fb-dimms are the hottest parts in these machines, but the nehelem thermal issues were reported across the line (ie, not restricted to Xeons and even including in laptop usage.)
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Originally Posted by TAFKAT Yes the laptops will run considerably hotter at idle to moderate as well, but under load there shouldn't be any more heat stress placed on them.
I think the problem with the MacBooks running way too hot was that the fans never ran fast enough to efficiently cool the chips sufficiently , add to that a design that was focused more on form over function. Not sure about the Nehalem MACPro's, haven't really been following the chatter about temps there, more so just the lack luster performance. |
I think the fans were one issue, though that was supposedly addressed with a later patch (which people then complained about because it was making their fans louder.) There are also gpu issues mixed in there as well, but the heat dissipation issues of Apple's laptops is a notorious issue (and a soft spot from the G5 days for Apple fans.) It's been my guess that this is why we haven't yet seen anything beyond Core2 for Apple even though it's been on the market now for almost half a year.