Info, tricks & tips
INTRODUCTION TO OC'ING BY SHAMINO
CPU VTT: It is a Crucial voltage when pushing the Host clock, the Uncore Frequency, and the Memory Frequency. Default voltage will give around 1.165v. A good setting lies in the region of +250mv to +400mv. (The higher you push Uncore Frequency and Memory Frequency, the more you need typically)
- QPI PLL VCore: Can be more useful towards the high speeds of QPI Link (4.8GT/s, 5.6GT/s, 6.4GT/s). I usually Synchronize with IOH Vcore. I usually use 1.40 to 1.45v.
- DIMM Voltage: It is a Crucial voltage when pushing the Host clock, the Uncore Frequency, and the Memory Frequency, and the Memory Timings. The higher you push Uncore Frequency and Memory Frequency, the more you need typically. Or when you try to run low values for the Memory timings.
- IOH VCore: This can help when pushing Host Clock and when pushing PCIE Frequency and when pushing Multi-GPUs OC Setup. I usually synch at same levels as QPI PLL Vcore and use 1.40 to 1.45v. Raja1 has used 1.5+v when pushing really High Host Clocks.
VTT PWM Frequency: It controls the Switching Frequency for CPU VTT power supply. The higher the Frequency, the lesser the ripple, while the Mosfets work harder and warmer the higher the Frequency. I tend to use 610KHz though, since the current draw is not humongous here and the Mosfets handle the load like a piece of cake.
CPU PWM Frequency: It controls the Switching Frequency for CPU VCore power supply. The higher the Frequency, the lesser the ripple, while the Mosfets work harder and warmer the higher the Frequency. I tend to use 933KHz to 1200KHz, with the hot running i7 CPUs, since the Mosfets/Chokes are right beside the CPU, the heat from the CPU inevitably will spill onto the components here.
CPU Impedance: It is a Compensation Value for the Impedance/resistance of the CPU. Since the CPU socket pins has more gold than typical, lesser compensation is usually needed. As CPU temperature will also affect the impedance, when using a good aircooler or better cooling, I select the option “Less”.
QPI Signal Compensation: It is a Compensation Value for the IOH (Northbridge). Auto to less usually works better for me, but as IOH is a chipset and every chip maybe slightly different, the sweet spot setting for overclocking will have to be experimented with.**Note that CPU Impedance and QPI Signal Compensation are mere Signaling Compensation Values and will NOT harm your hardware in anyway at any setting. Also note that PWM Frequencies selection are all thoroughly tested at every option and are Stable Frequency Selections Safe to run.
- tRAS: 21 to 25 is a usual spot when you are maximizing the Memory Frequencies, and once you drop down to 19 and below, it is ‘Tight’ to the Memory and may result in instability or requires more voltage to run.
- tRFC: This is also very dependent on how high you’re running the Memory frequency and the voltage you feed Memory. 88 seems to be a high enough spot when you’re trying to max out the Memory Frequency, and when you do sub 70 timing on this one, be prepared to feed enough VDIMM. 59 is a great performance value, but you may not get the same overclocks or may need a big amount of voltage when you’re running 2000+ Frequencies.
Overclocking the Intel I7
Note: Just because these settings work in my case, they may not in all cases depending on the components, it is best to use this as a base or a guide and tweak from there.
Also, this guide will use an Intel 920 as an example, if you have an Intel 965, it will be a different experience since you will have an unlocked multiplier, you will not need to rely on adjusting the QPI frequency.
So lets talk about our goal, our goal is as follows:
- Using an Intel 920, overclock to at least 4.2GHz on air.
- Run DDR3 memory in Triple Channel at 1600MHz, 9-9-9-24.
- Run a QPI frequency of 200MHz or higher.
1. So the first thing we want to do is go into the BIOS, and press "Load Defaults", save and exit and go back into the BIOS and navigate to "Frequency/Voltage Control" 2. Next we will adjust the following options:
3. Next we will go under "Memory Feature" and adjust my memory to it's specifications. In my case, I am running 1600MHz memory so I will make the following adjustments:
- CPU Clock Ratio to 20x.
- CPU Host Frequency (AKA QPI/BClock) to 200MHz.
- CPU Uncore Frequency to exactly double my memory multiplier, in this case 16x.
- This will give me exactly 4GHz (20x200), but we want 4.2GHz or more so keep reading...
4. Next, and probably most importantly, we will need to adjust the voltages. Under the "Voltage Control" I made the following adjustments, and please note, you may need to tweak this further for better stability, and/or better temps.
- Memory Frequency to 2:8.
- Memory timings adjusted properly per memory specifications.
- This will give me 1600MHz memory. (200x8)
- Set the tRFC Setting to 74
5. Finally, on the "CPU Feature" page, we will make the following critical changes:
- EVGA VDroop Control - Without VDroop
- CPU VCore - 1.47500V (note, this is just an example)
- CPU VTT - +300mV
- CPU PLL - Auto
- DIMM Voltage - 1.65V
- DIMM DQ Vref - +0mV
- QPI PLL VCore - 1.400V
- IOH VCore - 1.400V
- IOH/ICH I/O Voltage 1.650V
- ICH VCore - 1.250V
- PWM Frequency - 1067 KHz
- Disable all of the Intel Power saving features.
- Enable "Turbo Mode Function" (this will give me a 21x multiplier in some cases!)
- Change my QPI Frequency Selection to "4.800 GT/s.
6. Oh yea, we will increase the fanspeeds:
7. Now, in Windows with EVGA E-LEET we are at 4.2GHz! But we're not done yet!
8. On the memory tab we can see our memory is running at 1600MHz (800x2) Just like we wanted.
9. So now lets push it some more, using EVGA E-LEET, we will go to the overclocking tab, and are going to try increasing the QPI Frequency to 205MHz. This puts me at 4300MHz... still ok...
10. Lets keep going! Up to 215MHz! That is over 4.5GHz on air!
11. Next I will save a validation file in EVGA E-Leet and upload it for bragging rights
THANKS TO EVGATech_JacobF; Shansmi
The Voltage Guide
The voltage you set is not necessarily the voltage you get
. Furthermore the voltage you read is not necessarily accurate either. The Eleet utility (along with any other software monitoring utility) will simply report what the motherboard tells it to report. When measured independently, these readings are close, but not entirely accurate
VCore (default: 1.28125v, Intel's max 1.375v, VCore over 1.50v on air cooling is risky) What it does:
Sets max voltage to the CPU cores. (if Vdroop is disabled, it will set the min voltage instead) The i7 doesn't need much voltage at speeds under 3.8ghz. (For example, I can get 3.8ghz on 1.275 vcore) Beyond that the voltage requirements climb sharply. When to raise VCore:
- BSOD 101 "Clock Interrupt not received from Secondary Processor"
- LinX produces errors that are very
- LinX errors happen within 1 min of LinX
- LinX produces BSOD within the first minute
You know VCore is too high when:
- CPU cores approach a peak of 85c on full load
- It is unknown how higher voltages may impact the life of the CPU
CPU VTT Voltage (default: 1.1V (+0mV in BIOS) Intel's max 1.35 (+250mV)
What it does:
VTT connects the cores with the memory. Raising VTT helps keep a system stable at higher QPI rate. Since QPI is calculated from bclk: the higher the bclk the more VTT voltage you will need. VTT is also called "QPI/DRAM Core" on other motherboards,
Prevent CPU damage: VTT voltage must be within 0.5V of VDimm. Vdimm can fluctuate by as much as 0.05V from settings so you may want VTT within 0.45V of VDimm for that extra margin of safety. Example: if Vdimm is 1.65V, then VTT must be at least 1.20V.
When to raise CPU VTT Voltage:
- BSOD 124 "general hardware failure"
- LinX errors happen only after 10 min or more
- LinX hangs but does not BSOD
- LinX reboots without BSOD
You know CPU VTT Voltage is too high when:
- Most users try and stay below 1.45V (+350V) for 24/7 use without additional direct cooling.
- The motherboard doesn't read the temp so you may need an IR thermometer to be sure you are not pushing VTT too far.
CPU PLL VCore
(default: 1.800V, spec range: 1.65V-1.89V)
What it does:
Keeps CPU clock in-sync with bclk.
When to raise CPU PLL VCore:
- May help with stability while increasing the bclk or CPU multiplier.(or may make it worse)
- May help with stability past 210 bclk if you observe that during runtime the QPI Link (found in E-Leet) bounces too much.
- Not a commonly raised. May actually cause instability. Test this variable alone.
You know CPU PLL VCore s too high when:
- Its possible you could actually gain stability by lowering this.
(default: 1.5V, Intel's max 1.65)
What it does:
Voltage to the RAM. Despite Intel's warnings, you can raise voltage beyond 1.65 as long as it is always within 0.5V of VTT (as described above).
When to raise DIMM Voltage :
- High performance/gaming RAM usually requires at least 1.65v to run at spec. Some manage to get it slightly lower.
- Stable bclks over 180 often require VDIMM beyond 1.65V. Remember to keep VTT voltage within 0.5V of VDIMM.
You know DIMM Voltage is too high when:
- Memory is too hot. [more info on this is needed]
DIMM DQ Vref
What it does:
It is the reference voltage for a pseudo-differential transmission line. The DQ signals sent by the memory controller on the i7 should swing between logic-hi and logic-lo voltages centered around VREF. VREF is typically half way between the drain and source voltages on the RAM. Most VREF generator circuits are designed to center between the VDD and VSS voltages on the RAM. There is usually temperature compensation built into the circuitry as well.
When to raise DIMM DQ Vref:
- Vref might be adjusted if (after measurement) it was determined not to be properly centered between VDD and VSS of the DIMM. Without a good osciloscope it's difficult to imagine that most users could set VREF correctly. They may be able to set VREF empirically by moving it up or down and checking for POST or BSOD problems.
QPI PLL VCore
(default: 1.1v, <1.4v is pretty safe)
What it does:
Keeps on-chip memory controller in-sync with bclk.
When to raise QPI PLL VCore:
- Try raising this along with Vcore and VTT, but in smaller increments.
- Helps stabilize higher CPU Uncore frequencies and QPI frequencies (in CPU feature)
- Try raising this when you increase memory clock speed via multiplier.
- Try raising when LinX produces errors after a few minutes without BSOD
What it does:
Sets voltage for on-chip north bridge which connects PCIE2.0, GPU, Memory, and CPU.
When to raise IOH VCore:
- Possibly needed if you overclock your north bridge (via bclk and CPU Uncore freq.)
You know IOH VCore is too high when:
- Memory errors? (just a guess)
- GPU intensive apps like 3dmark vantage crash. (another guess)
IOH/ICH I/O Voltage
What it does:
some sort of on-chip bus voltage. unknown
What it does:
South Bridge chip on the motherboard. Connects all motherboard features, cards (not PCIE2.0), and drives to CPU/memory on IOH
When to raise ICH Vcore:
- I don't know if raising this can help in overclocking at all. Possibly necessary in order to keep up with an overclocked northbridge?
You know ICH Vcore is too high when:
- unknown. I wouldn't overvolt it too much though.
What it does:
When to raise PWM Frequency:
- Overclocking beyond 4.2ghz
You know PWM Frequency is too high when:
What it does:
Safety feature designed by Intel to protect the chip from excessive wear from voltage spikes. Enabling VDroop keeps actual voltage running below the VCore setting in BIOS
What does disabling VDroop do?
- Makes VCore setting the minimum value for actual voltage; CPU will run at higher voltages than what you set in BIOS.
- Disabling VDroop is the same as enabling Load Line Calibration on other x58 boards.
Why would I want to disable VDroop?
- Some overclockers use it because it allows them to get a high overclock while setting lower VCore in BIOS. This is because the running voltage is actually higher than what was set in BIOS. Disabling VDroop keeps actual voltage higher than what is set for VCore in the BIOS. Enabling Vdroop keeps actual voltage lower than VCore.
- It might help if you are pushing the bleeding edge.
The Diagnosing errors
- BSOD "IRQL_NOT_LESS_THAN_OR_EQUAL" (I forget)
- BSOD 101 "Clock Interrupt not received from Secondary Processor" Try raising VCore
- BSOD 124 "general hardware failure" Try raising VTT
If you get an error you would have x same (correct) results and 1 different (an error):
- If the incorrect result differs slightly from the rest (numbers very close, same powers in Residual & Residual (norm)) it is most likely that there's not enough vcore. In this case only a small vcore bump is usually needed to stabilize the system (alternatively, Vtt & GTL tweaking can sometimes fix this too)
- If the wrong result differs much from the others (different power or even positive power in Residual or Residual (norm)) it might be 1) insufficient vcore (the error would happen at the very first runs then) or 2) some memory / NB instability (when it worked for say 10 minutes ok and then produced a different result)
More serious LinX errors:
- BSOD during testing (at the very first runs) is often caused by too low vcore
- System hangs and remains hung it is almost 100% not a CPU but memory or possibly NB issue
- System reboots (with no hang prior to reboot and no BSOD) - a CPU issue, but not vcore related (insufficient PLL or Vtt I guess)
- System hangs for a short while and then BSODs - once again NB or memory problem (but might be wrong Vtt / GTL setting as well)
- System hangs and then just reboots - wrong Vtt (too low or too high) or GTL settings
Thanks to FreeMortal