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Message: <blockquote data-quote="chanaka89" data-source="post: 3558114" data-attributes="member: 51319">[code]FSB : DRAM1:1 = 333 MHz : 667 MHz4:5 = 333 MHz : 833 MHz 2:3 = 333 MHz : 1,000 MHz5:8 = 333 MHz : 1,066 MHz3:5 = 333 MHz : 1,111 MHz1:2 = 333 MHz : 1,333 MHz[/code]Now, if you’re running @ a 400 MHz FSB, the ratios become:[code] FSB : DRAM1:1 = 400 MHz : 800 MHz4:5 = 400 MHz : 1,000 MHz 2:3 = 400 MHz : 1,200 MHz5:8 = 400 MHz : 1,280 MHz3:5 = 400 MHz : 1,333 MHz1:2 = 400 MHz : 1,600 MHz[/code]You can calculate these yourself with this formula:[code]DRAM Final Clockrate = (2 x FSB)/Divider[/code]Example, 2/3 divider @ 400 MHz FSB: (2 x 400 MHz)/(2/3) = 1,200 MHzRunning in 1:1 mode is termed, “synchronous mode.”  If you use a higher frequency, you’re running is so-called “asynchronous mode” which offers marginal speed advantages at the price of more heat and power consumption on a C2D/C2D Quad-based system for most users.  Depending on your chipset, running in an asynchronous mode may require more vcores to some of your motherboard components such as the NB, IHC, and/or FSB Termination (more on these later).    PCI Express Frequency – Set this to 100 MHz.  If you don’t, I believe the PCIe bus speed will increase proportionally with your FSB which is something you DON’T want to do to your expensive video board.PCI Clock Synchronization - Use 33.33 MHz here.  Again, if you leave the setting on auto, the PCI clock will creep up proportionally with your FSB which can damage cards you may have there aren't designed to run at higher frequencies.Spread Spectrum - disable.Memory Voltage - Read the specs for your memory.  My DIMMS can use up to 2.2v.  You can damage your memory if you overvolt it.  CPU VCore – THIS IS KEY!  This single BIOS setting will have the largest effect on your processor’s operating temperatures!  Again, read on to the section entitled, “Stress Testing and Minimizing Your Vcores.”It needs to be enough to run stable, but not too much or else you’re just wasting power and creating a ton of heat.  This is particularly true with multicore processors!In case you’re wondering what Intel recommends for your processor, find your chip on <a href="http://processorfinder.intel.com/Default.aspx" target="_blank">Intel's Processor Finder</a>.  The Q6600 is between 0.85 – 1.5V.In my experience, a setting of “auto” ALWAYS over-estimates, but for your first boot, just leave it on auto.  The next section of this guide covers stress testing whose goal is to verify stability and to minimize your vcore. For example, once you verify that you can run stable for several hours of stress testing, you'll want to come back and minimize this voltage until you become unstable again.  Then simply add a little back. As you can see, my system runs stable @ 9x333 using 1.2625v.The last four voltages are also required to make a stable system.  Leave them on auto for now.  On my system, I lowered my chipset temps by about 4 °C by lowering them to the values you see in the pic.As I mentioned earlier, if you’re using high memory dividers (a.k.a. running your memory in asynchronous mode), you might have to manually tweak your NBvore and your ICH vcore to get the memory to run stable.  For example, my Q6600/P5B-Deluxe system required me to up the NB vcore by +2 steps and the ICH vcore had to be set to the maximum value or else I couldn’t run my PC1066 memory at the higher dividers. My X3360/LT P35-T2R system on the other hand, didn’t require nearly that much extra to run in the 5:6 divider.In general, the P35 chipset is better than the P965 in this regard.  I have read that the X38/X48 are on par or slightly superior to the P35. Okay, save your settings and hopefully your machine will complete the POST.If it doesn’t, and assuming you set your voltages to Auto, some common reasons are:•    Memory voltage too low•    Memory timings too aggressive•    FSB too aggressiveIf you complete the POST, and make it into windows without a blue screen or reboot that's a good sign.  Now on to the testing.  Now that you're in Windows, load up CoreTemp or HWMonitor and have a look at your core temps when idle.  <img src="http://img169.imageshack.us/img169/3471/9x333ar4.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />They should be well under 50 °C unless it's REALLY hot in your room, see the end of this document for more on how ambient temps affect your CPU load temps.  There are a number of things you can do to bring down your idle and load temps.  Again, see the end of this guide for some suggestions.  Let's stop here and figure out what the red-line for temps should be... for my B3 stepping of the Q6600, I don’t want to exceed a few degrees over Intel's 62 °C limit for any sustained period of time.  The G0 stepping chip tolerates 71 °C, so you're probably safe a few degrees above that.  You can decide on your own "red line" if you disagree with my admittedly conservative numbers.  Here is some information you can use to help:  <a href="http://processorfinder.intel.com/Default.aspx" target="_blank">Intel's Processor Finder</a>.  Read the Thermal Specification section. Wondering what the deal with the stepping of the chip is?  Have a look at <a href="http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3066" target="_blank">this article</a> that will explain it as well as show you some differences between the new G0 stepping quads.I may be misunderstanding it, but as I read it, the thermal specs are the upper limit for the "case temp."  No C2D or C2D quad processor actually has a sensor for "case temp" as defined by Intel.  To measure this, you would need to place a sensor on the top of your IHS right in the center.  C2D/quads have INTERNAL sensors (called DTS or Digital Thermal Sensors) but not external sensors.  Some software and BIOS's can approximate this "case temp," but without a physical sensor there, you're just guessing.  The formula for reading core temp from the DTS is:[code] Core Temp = tjmax – DTSWhere DTS is the number the DTS is reporting, and tjmax is a constant (which differs with processor model and sometimes within a processor model based on its stepping)[/code]Note: There is no official communication from Intel as to the magnitude of tjmax for desktop/server C2D/C2Q chips!  This makes calculating the “real” core temp tough since people are just guessing.For example, a Q6600 (G0) stepping may have a tjmax of either 95 or 105 (again, these are people’s best guesses).  If tjmax is 105, then Core Temp = 105 - DTS.  THIS DOESN'T MEAN THAT THE LIMIT FOR THE CHIP IS 105 °C!  In this example, let’s say the DTS value is 50.  Therefore, Coretemp = 105-50 = 55 °C.  If tjmax is 95, the math becomes 95-50 = 45 °C.  Don’t worry about doing this calculation; all the temp monitoring software will do it for you.  I only mention it so you can understand what’s going on.I like to keep my core temps under 65 °C.  I may be using a conservative number here, but I don't want to replace my chip anytime soon.  If you don’t care about the longevity of your chip, you can likely use higher numbers.  I have read about people running their chips right up to the factory shutdown/auto throttle down temp.  It’s your chip, do what you want.Load up CPU-Z to see what your vcore is at idle.  <img src="http://img263.imageshack.us/img263/4551/ooey0.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />You’ll notice that the vcore in CPU-Z is different from the value you selected in your BIOS.  This is normal and true for all boards.  You’ll also notice it drops again when your machine enters a load state: again, this is normal and known as vdroop; some boards/chipsets do it worse than others.  If you read at the end of the guide, some boards can be modified to eliminate or greatly reduce vdroop.Stress Testing and Minimizing Your VcoresThe goal of stress testing is two fold:1)    To arrive at a stress test stable system (>24 hours with no prime95 errors).2)    To minimize your vcores and thus minimize heat product both on your CPU but also on your NB/SB and other MB components.Prime95 will run and every now and then it will check the values it’s calculating using your processor to its internal standards since its torture testing using known values.  Assuming you enable error checking, you’ll be notified if your values differ indicating an instability.  This is why it is IMPERATIVE that you enable error checking within Prime95; again, if you don’t enable it, you WILL NOT be notified of errors!  Do so simply by going to the “Advanced” menu and enabling “Round off Checking.”  If the system isn’t stable, it will report an error and stop stressing the core that gave the error.  <img src="http://img508.imageshack.us/img508/4359/royl8.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />Now that you picked your operating condition (i.e. 9x333 or 8.5x400, etc.) let’s stabilize the system through stressing it with prime95.  Just so you get an idea what to look for, Coretemp as well as Prime95 (double-check that you enabled round off error checking) and run the Torture Test>Large FFTs.  You’ll wanna keep an eye on your system temps to make sure they don’t exceed the redline so the chip doesn’t get throttled (assuming you have thermal management enabled in your BIOS).  All your cores should get stressed equally (look in the task manager to verify):<img src="http://img240.imageshack.us/img240/5851/dddpm2.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />For your reference, here’s what an error from within prime95 looks like: <img src="http://img169.imageshack.us/img169/3056/p95ss9.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />When/if you get an error (and you will), you’ll need to either back off on the operating conditions (FSB or multiplier) or add some voltage to your vcores.  Therein lies the challenge.  Since you have four different vcores to select from, how do you know which one or which ones to adjust?It’s now time to minimize your vcore settings.  Reboot and go into the BIOS’ section where you can control your CPU and MB voltages.  Remember, different motherboard will call these variables different terms.  The pic below is right out of my BIOS so you can see what DFI calls them, and what they mean:CPU VID Control – The processor vcore, I’m not sure why DFI calls it “CPU VID Control” but whatever.  From here on out, I’m going to call it Vcc since technically, the term VID is an entirely different concept (see <a href="http://download.intel.com/design/processor/datashts/31559205.pdf" target="_blank">this document</a>, page 14 for more if you have an interest).DRAM – The memory vcore.SBCore – Southbridge vcore (might be called ICH in your board).NBCore – Northbridge vcore (might be called MCH in your board).VTT – Reference voltage (might be called FSB Termination voltage in your board).  It’s used to terminate data lines between the MCH and CPU.<img src="http://img376.imageshack.us/img376/8703/biosjy3.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />Some motherboards give the option for GLT reference controls.  If you enable this you’re adding three additional variables to the mix and making your life more complicated.  Unless you’re an extreme overclocker wanting to squeeze every single MHz out of your system, my advice is not to enable the GLT options.  I’d also caution you not to enable this option since there is tons of misinformation out there about these undocumented features.If you must, here a few links that might help you understand how it works and give you some starting points, but I won’t be using them in this guide:<a href="http://www.thetechrepository.com/showthread.php?t=87" target="_blank"> Adjusting [Advanced] Gunning Transceiver Logic (A/GTL+) Voltage Levels for Increased Front Side Bus (FSB) Signaling Margins and Overclocking. </a><a href="http://www.anandtech.com/mb/showdoc.aspx?i=3129&p=1" target="_blank">DFI UT P35-T2R: Tweakers Rejoice!</a><a href="http://csd.dficlub.org/forum/showthread.php?t=6301" target="_blank">Good thread (kinda long) but good info.</a>There are several approaches you can use to arrive at a stable, minimized set of vcores.  I recommend that you start with lower vcore values and work your way up.  Lower values will fail much faster than higher values thus making the process a bit quicker for you.To start with, select a set of vcores that are kinda low and see if you can POST.  How do you know where to start?  Use trial and error at this point unless you know someone else’s settings to use as starting points.  When in doubt, I’d recommend that you start near the bottom of the scale.  Here are some rough guidelines for setting your VTT:1.2-1.3V - for a FSB of ~400 MHz.1.4-1.5V – for a FSB of ~420-440 MHz (exceed 1.4V at your own risk with a 45nm chip)!1.6V – for a FSB of ~440-475 MHz - use at your own risk with a 45nm chip!You should be aware that newer 45nm fab chips are MUCH less tolerant toward high VTT than their 65nm predecessors.  Anantech published their experience <a href="http://www.anandtech.com/weblog/showpost.aspx?i=428" target="_blank">frying a QX9650</a> with high VTT’s as an example.Vcc – Initially, set within 200-400 mV of where the auto setting used (remember that you need a little more in the BIOS compared to what CPU-Z told you).  Remember to consult <a href="http://processorfinder.intel.com" target="_blank">Intel’s processor finder</a> to know where the upper-end of safety is for your processor (I believe the figures there correspond to the values CPU-Z is displaying, not what you set in the BIOS.).DRAM – What ever the RAM manufacture recommends is a good starting point.  Unless you’re really overdriving them, they shouldn’t need more.SBCore – I’ve always used the lowest setting, but I typically don’t push my systems that hard (20-25 %).  You’re on your own here.NBCore – Start off low, 1.33 or 1.37 and see if you need more.  Also, a little bit can go a long way.  My system is unstable @ 1.330V here but stable @ 1.370V which is a difference of only 40 mV (0.04V).Here are the levels my Q6600 @ 9x333 uses to run stable:[code]Memory Voltage=2.100VCPU VCore=1.2625VFSB Termination=1.200VNB Vcore=1.25VSB Vcore=1.50VICH Chipset=1.057V[/code]Here are the levels my X3360 @ 8.5x333 uses to run stable:[code]CPU Vcc=1.00000VSB 1.05V=1.070VNB Core=1.330VSB Core/CPU PLL=1.550VCPU VTT=1.100V[/code]Note that I haven’t refined these last settings (for 8.5x333) and don’t plan to <img src="/styles/default/xenforo/smilies/default/happy.gif"  class="smilie" loading="lazy" alt=":)" title="Happy    :)" data-shortname=":)" />  For example, I think it would work with a lower Vcc and NB, but I don’t care enough to test it (these are good enough).I show those only to give you an idea, not all hardware is the same, and really, those values are personal to my chip, RAM (and RAM settings), MB, etc.!Once you select a baseline set, that will complete a POST, you’ll want to start a more vigorous evaluation by changing the MB vcores one-at-a-time moving forward.  If you change too many variables at once, you’ll never be able to arrive at the stable settings.  Confused?  Don’t be, just read on and after you see the examples, I think the process will seem clearer to you.The basic process is to try different Vcc values keeping the other vcores constant.  Run p95 at a given Vcc and record what happens after an arbitrary time point (10 to 15 min is good to start with).  If Vcc level is stable for 15 min of p95, reboot and lower it a little and repeat.  The goal is to find the minimum level that gives errors, then increase it until it’s stable, then extend that time out to say 2-4 h.  If it’s still stable, further extend it to 10-14 h.  You can probably call it “stable” if you can run p95 for 24 h.  If a setting fails after 4 h, increase it one notch or so and repeat until it’s stable out to 24 h.  You can then come back knowing this Vcc and try to lower one of the other vcores repeating the process. Yes, it’s time consuming and yes, it’s tedious, and yes, that’s a ****load of rebooting, but it works.The key to this process is keeping a detailed record to help you achieve a stable system and troubleshoot which vcore to change – p95 errors are NOT always the fault of a low Vcc!  Without these data, you’ll have a tough time.  So what do you keep track of here?  1)    The MB vcores you’re using2)    The Vcc values you’re testing3)    Which core failed (prime95 tells you) and how long it took to fail4)    Any observations or comments you want to record for yourselfHere are two examples minimizing vcores using my X3360/P35-based system.  The data presented aren’t fabricated to help illustrate the method; rather, they are the real data I used to arrive at the stable system.  Also know that to really really do this right, you’d need to do several runs at the various levels; doing it just once as I am is the quick ‘n dirty approach and can cause you to draw an incorrect conclusion or two as you will see.Example 1: 8.5x400Hardware specs for your reference: I set up my MB vcores and began testing Vcc starting low (I chose 1.12500V somewhat arbitrarily).</blockquote>

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