Overclocking Intel's New 45nm QX9650: The Rules Have Changed
by Kris Boughton on December 19, 2007 2:00 AM EST- Posted in
- CPUs
An Unexpected Loss of Performance at Higher Speeds
It looks as though Core 1 is having trouble keeping up with the other three
We first suspected our motherboard's VRM circuitry might have been overheating while supplying the high load current. If this were the case the PWM IC would communicate with the processor using the PROCHOT pad and the CPU would respond by modulating an internal clocking signal to each core thereby artificially lowering the load and allowing the VRM to cool - a failsafe meant to save the VRM should things start to get too hot. Eventually our frustration in the matter led us to modify our board by disconnecting the control signal altogether. Unfortunately, there was no change.
We discussed the possibility of having discovered an undocumented erratum, thinking that maybe some internal control logic was at fault. The Analog Devices ADP3228 PWM controller used on the ASUS P5E3 motherboard, designed in compliance with Intel's new VRM 11.1 specification, includes a new power management feature intended to improve power circuit efficiency during periods of light loading. When directed by the CPU the VRM essentially disables four of the eight power delivery phases until they are later command back on. (This is not unlike the concept put to use in the automobile industry wherein half an internal combustion engine shuts down while cruising in order to improve fuel economy.) However, we are unable to completely rule out a possible incompatibility as no one is aware of how to go about disabling this feature.
In fact, we believe what we are seeing may be nothing more than a CPU protection mechanism in action. The Core 2 family of processors is extremely resilient to abuse - reports of failures due to overvoltage or over current incidents are exceedingly rare. Features such as these work by clamping processor input voltage (and current) to tolerable levels in order to prevent permanent damage. Further testing reveals we have some level of control with regards to the "throttling" - it seems that by slightly lowering the VID, and thus in turn the CPU supply voltage, we are able to complete testing at some of the same frequencies with no noticeable performance degradation issues. Could it be possible that we found a processor protection limit with nothing more than common water-cooling? Normally, such discoveries are the domain of those that freeze their CPUs with one or more rotary compressors or copious amounts of liquid nitrogen. Given the enormous power increases observed at these higher speeds due to what might be a processor capacitance effect, we cannot help but wonder if these new limitations are an unintended consequence of Intel's 45nm process.
If what we believe is true the implications could be enormous. The need for certain industries built on delivering high-performance cooling solutions to the overclocking community would be largely invalidated. What's the point in spending more money on a more effective heatsink if there's nothing to gain? With that said, we honestly believe a new direction in CPU overclocking may soon be upon us. While there will always be those that continue to push processors to their absolute limits, the majority of us will find our new "performance" benchmark in efficiency. This makes sense though - the market has been heading this way for years now and overclockers may have simply chosen to ignore the obvious. The multi-core era we now live in places a heavy emphasis on performance-per-watt figures and other measurable efficiencies. Does anyone else find it odd that Intel's flagship product, the QX9650, comes at exactly the same speed bin as the previous 65nm offering? All this talk of improved performance and efficiency and not even a measly frequency bump - perhaps Intel is trying to tell us something.
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Kougar - Thursday, December 20, 2007 - link
This was the exact type of article I love to sit down and read through. It doesn't matter if portions of it are above my head, it just gets me to rise up another level to grab at them. Your article was a great read and I very much hope to see many more like this one in the future!Regarding the P5E3, I am somewhat surprised that 0.81v was the lowest you could set. Even the budget board P31-DS3L offers 0.51v as an option, my personal P35-DQ6 has 0.50v as a vCore option. I found your commentary regarding Load Line Calibration to be illuminating... this is exactly what enthusiasts like myself and others need to know.
Lastly, I hate to ask here but Google was no help, Intel's ARK database didn't cover it, and Intel's datasheet didn't mention that I could see... what exactly is P35's process size and default vCore? The same as X38's...? As much as I love Gigabyte they are notorious for their lack of system voltage info...
kjboughton - Thursday, December 20, 2007 - link
The P35 and X38 chipsets are both made using Intel's standard 90nm process technology. It's not uncommon for chipset's to lag behind current CPU offerings by a whole process generation or more. With that being said, Intel's upcoming P45 chipset, the last of it's kind (recall that all future CPU technologies will make use of an onboard memory controllers) will be made on the 65nm process -- something even the X48 won't have. In fact, this reduction in process size may have considerable benefits for P45 when it comes to the reduction in power consumption and increased performance headroom, particularlly when overclocking. The P45 default Vmch is 1.15V, X38 is slightly higer at 1.25V. Based on this I would expect to see the P45 come in around 1.05V or possibly even lower.myocardia - Thursday, December 20, 2007 - link
Kris, great article. But, when did $400-500 worth of watercooling equipment become so commonplace, as to be putting the one (or is that two?) companies who make phase-change units out of business? If freon is no longer needed for extreme CPU cooling, couldn't Vapochill just start making even more expensive, higher-end watercooling?spamme33 - Thursday, December 20, 2007 - link
I have been overclocking since my first computer build years and years ago, rarely do I learn that much from one article. Very well written, informative, and timely!kilkennycat - Thursday, December 20, 2007 - link
The documentation accompanying the BIOS settings of almost all enthusiast motherboards is frequently obscure and incomplete - probably because it is printed many months before the board/BIOS is released, plus the leading manufacturers never bother to update BIOS user-documentation when they update the BIOS. Also, it does seem that the documentation authors have a uniformly poor grasp of the English language and prefer to keep descriptions of all BIOS settings as vague and incomprehensible as possible. It is also so common to find sundry BIOS entries not documented AT ALL anywhere in the motherboard manual, even the (so-called) latest on-line version.So I have a request on behalf of those like myself desperately trying to understand each entry in the BIOS of that brand-new and very expensive enthusiastic motherboard that I have just purchased, with that abysmal so-called user-manual and pathetic in-BIOS "Help" Function-key :-
Would it be possible for you or other at Anandtech to fully document/explain all the terms used in the text of the CPU and memory BIOS settings of the most popular enthusiast motherboards?
To keep such an exercise manageable, I suggest confining the exercise initially to existing and upcoming enthusiast desktop motherboards that are fully compatible with Penryn and Phenom. At present, X48, nVidia 780i, AMD 790FX.....
poohbear - Thursday, December 20, 2007 - link
thank you very much for such an informative and detailed article. very much appreciated for us overclockers and the future looks fantabulous w/ these cpus.wyemarn - Thursday, December 20, 2007 - link
Thank you very much for this great article. What a wonderful Christmas gift from Anandtech! This is one the most complete article I have ever read. CPU performance, overclocking, mobo settings, power consumption all in one article. What a joy to read.akaevile - Thursday, December 20, 2007 - link
Thank you for the detailed information. One has to be a little nervous however for the implications in what your work has found. Will Intel's improvements in refining 45nm technology push the line or has it been drawn in the sand??n7 - Wednesday, December 19, 2007 - link
Really superb article.Possibly the best i've ever seen on AT!
Thanx for the indepth info!
Bozo Galora - Wednesday, December 19, 2007 - link
looks like not only the X48, but three 45nm quads also will be delayed - due to AMD incompetence.http://www.digitimes.com/mobos/a20071218PD212.html">http://www.digitimes.com/mobos/a20071218PD212.html