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Turbo Boost Mode and CPU Overclocking Specifics

Let’s start with the fact that Intel DX58SO mainboard proved just as good as many other mainboards during work at high base frequencies. When we lowered the processor clock multiplier, the board performed stably and passed short tests successfully at 215 MHz frequency. It is a very good result. It guarantees that the board’s ability to reach high frequencies won’t stall our overclocking success.

Now we have to say a few words about the specific peculiarities of Intel DX58SO mainboard. First, all Intel processor power-saving technologies stay up and running, even if we increase the processor core voltage. You may have noticed that there are two parameters in the mainboard BIOS for adjusting the processor core voltage. If we use “Static CPU Voltage Override” to set the CPU Vcore the board will lock the voltage at this value independent of the current system load. If we add a certain value to the nominal voltage setting using “Dynamic CPU Voltage Offset (mV)”, Intel processor power-saving technologies continue working and lower the processor Vcore in idle mode in proportion to the initial setting increase. This is truly great news! Unfortunately, the acknowledged overclocker mainboards from Asus and Gigabyte, can’t boast anything like that.

The next thing worth mentioning has to do with Intel Turbo Boost implementation during Core i7-920 CPU overclocking. So far we are familiar with two implementation approaches. We come across the first one during our tests of Asus and Gigabyte mainboards. Even under very heavy CPU utilization its clock multiplier still increases to 21. We only saw it drop to the minimal value of 20x when the CPU temperature exceeded 94 °C and overheating protection kicked in on Asus P6T board. Another implementation of Intel Turbo Boost was revealed during MSI Eclipse Plus tests. Only under relatively small load the processor clock multiplier increased to 21. When the load was fairly high, the processor power consumption and temperature started growing, and the board returned the clock multiplier back to its initial value of 20x. Intel DX58SO mainboard also behaves differently, although I believe I should change the term here. Intel should know best of all what the right implementation of Turbo Boost technology is, shouldn’t they? So, we should call this particular implementation “correct”, and another one “different”.

In fact, “correct” is not necessarily the best, each approach has its advantages and drawbacks. Obviously, the boards that always increase their clock frequency multiplier to 21x will perform better in heavy multi-threaded applications, because their rivals with “correct” technology implementation will have their multiplier at the nominal value. However, as our recent tests of MSI Eclipse Plus mainboard showed, this advantage is not always indisputable. Since the board lowers the clock multiplier to its nominal value under heavy load, the resulting CPU frequency also lowers, which allows us to raise the base frequency a little higher during overclocking. As a result, the performance difference under heavy load is not that dramatic anymore. Moreover, under moderate load in a number of applications MSI Eclipse Plus would even take the lead due to higher base frequency.  In those cases when the multiplier is increased to 21 the CPU frequency is higher and so is the memory frequency. Since heavy multi-threaded applications are still not so widely spread as applications creating moderate single- or dual-thread load, the “correct” Intel Turbo Boost implementation appears of bigger benefit to “typical” users.

Overall, our updated terminology again doesn’t really depict the actual state of things, because the “correct” implementation is not always good, and the “incorrect” implementation is not that bad and can provide even higher performance in a number of cases. Therefore, I suggest that from now on we should use the term “dynamic” for the “correct” implementation of Intel Turbo Boost technology, because in this case the multiplier changes (increases or lowers back to its nominal value) depending on the workload. As for the “incorrect” implementation, we will call it “static”: the multiplier is always one step higher, no matter what the workload is. Just in case I would like to remind you that we are talking only about overclocking here. In the nominal CPU mode almost all mainboards we have tested so far employ “static” approach: no matter how heavy the load is, the multiplier is always set one step higher. At least, this is true for Intel Core i7-920 processor, because its power consumption never exceeds the acceptable limits in the nominal mode under any workload. And in both cases the multiplier will go down to the minimal value of 12 (passing through a number of intermediate lower values), if the workload lowers or disappears completely in idle mode.

But what if you are not a typical user and there are quite a few heavy-duty multi-threaded applications among your everyday tasks? Does it mean you will have to avoid mainboards with dynamic implementation of Intel Turbo Boost technology, if you create and process multimedia content, work with models, sound images or video? In case of MSI Eclipse Plus mainboard, it might be not the most optimal choice for you. However, the BIOS of Intel DX58SO mainboard has a beautiful parameter called “CPU VR Current Limit Override”. Once it is set to “Enable” the board stops reacting to high current received by the CPU, its multiplier no longer lowers to 20x in case of heavy load. Intel DX58SO mainboard allows easily switching from the dynamic implementation of Intel Turbo Boost technology to a more convenient and beneficial in this case static implementation!

Frankly speaking, by this time all my initial skepticism about Intel being able to make a good overclocker mainboard was gone. Intel DX58SO mainboard seemed to be an ideal universal overclocker mainboard. See for yourselves:

  • Nothing restricts CPU and memory overclocking;
  • Even when the processor core voltage is increased, Intel processor power-saving technologies continue working;
  • You can select the most appropriate Intel Turbo Boost implementation for your needs.

Unfortunately, I forgot that there is no such thing as an ideal mainboard, but one more peculiarity of the Intel DX58SO solution reminded me of that. During our experiments, I discovered that “Enhanced Power Slope” parameter that should prevent the processor core voltage from dropping under heavy load, works too well. We have already seen many times that enabling parameters like that on different mainboards caused the voltage to increase instead of going down, and sometimes this increase appeared quite significant. For example, DFI LanParty JR X58-T3H6 or EVGA X58 SLI Classified. To our great disappointment, Intel DX58SO is also one of them. We easily overclocked our system to 185 MHz base frequency using the dynamic implementation of Intel Turbo Boost technology. We have already demonstrated the effectiveness of this overclocking during our tests of MSI Eclipse Plus mainboard. We spend the rest of our time trying to achieve stability during overclocking with a locked processor clock frequency multiplier, but without luck.

The most important thing during CPU overclocking is to ensure stable power flow. Trying to prevent processor core voltage from dropping under heavy load we set “Enhanced Power Slope” to “No Slope”. In this case the processor core voltage would constantly increase under heavy load even if we hadn’t increased it in the mainboard BIOS left it at the nominal value. As a result, after 2-3 LinX cycles the core temperature increased to 96-98 °C and then we saw the blue screen of death or terminated the tests ourselves. By the way, I believe that Intel engineers are very well familiar with the problem of voltage increase under heavy load that is why they introduced this strange intermediate “50% Slope” value of the “Enhanced Power Slope” parameter. In other words, let the voltage increase, but not as dramatically as in case we set this parameter to “No Slope”. We have never seen anything like that on any other mainboard, but it didn’t really help: the voltage increased a lot anyway.

Ok, we gave up the unsuccessful “VDroop” implementation and left “Enhanced Power Slope” parameter at its default value of “100% Slope”. To make up for the anticipated voltage drop under heavy workload, we had to increase it right from the start in the BIOS. It actually got totally absurd: power-saving technologies were formally working and increased core voltage did get lower in idle mode, but it dropped only to the level where it would normally go up to under heavy load. But even in this case, either the voltage wasn’t increased high enough, which caused the system to hang as soon as the voltage dropped down, or the voltage turned out too high and BSOD appeared after the temperatures jumped to 96-98 °C.

You don’t have to use Intel Turbo Boost technology to ensure that the CPU remains stable when overclocked with a fixed multiplier. Intel DX58SO mainboard can work fine even at 215 MHz base frequency. We only had to increase this frequency to 195-197 MHz to overclock our particular processor sample to the desired 3.9-3.95 GHz even without increasing the multiplier to 21. The multiplier is set to its nominal value of 20x, the load is pretty high that is why it won’t go any lower than that, but the system is again very unstable for the same exact reasons. Either the temperature is too high because of increased core voltage, or the voltage is insufficient to guarantee stability.

 
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