I7 920 D0 not stable at 4.2GHz

[phat_cow]

Hi,

 

I've been trying to get this cpu to be stable at 4.2GHz. My computer specs:

G.SKILL F3-12800CL9T-6GBNQ 6GB DDR3

Noctua NH-D14

Intel Core i7 920 D0 Stepping

Gigabyte X58A-UD3R

 

My BIOS settings:

 

 

anything I should do to make this stable? CPUZ says my Vcore is 1.312V and my temp never goes over 76 degrees when doing prime95 tests but it always crashes (BSOD) after an hour or so.

[ebarone]

My plan of attack would be to set your PCIe frequency to 100MHz (you have it at 101), try upping the vcore more, try downclocking your QPI multiplier, and maybe loosen your RAM timings and/or raise RAM voltage.

[CowKing]

maybe loosen your RAM timings and/or raise RAM voltage.

how do we know that it's the CPU that's not stable?

[ebarone]

We dont. But its pretty easy for RAM to limit an overclock, especially if his temps are okay. Theres a reason it was last in my list of ideas

[phat_cow]

We dont. But its pretty easy for RAM to limit an overclock, especially if his temps are okay. Theres a reason it was last in my list of ideas

 

Is it normal that CPU-z reports a different vcore then the one I selected in the BIOS? I selected 1.5v but CPU-z reports the vcore as 1.312

[nanoprobe]

1.5vcore is WAY to high for an i7 @ 4.2 GHz and your taking a chance of doing permanent damage. I would not run above 1.35vcore. I get 4.1GHz @ 1.24vcore.

 

Run HWMonitor and see what it reports as your vcore.

[phat_cow]

1.5vcore is WAY to high for an i7 @ 4.2 GHz and your taking a chance of doing permanent damage. I would not run above 1.35vcore. I get 4.1GHz @ 1.24vcore.

 

Run HWMonitor and see what it reports as your vcore.

 

I wonder if there's something wrong with my mobo because in the BIOS i set the vcore to 1.2625v and LLC to standard, but Easy Tune 6 and HWMonitor says my vcore is 1.232v. Thats a difference of 0.0305. I wonder if thats causing my OC problems?

[ebarone]

Ehh... maybe, but not in the way you might think. The difference (in your case .0305 volts) is called Vdrop. Not to be confused with Vdroop, which is something else entirely. Vdrop is an Intel thing, designed to protect your chip from over-volting. Vdrop is essentially the voltage buffer from the maximum allowed core voltage, ie the number you set in the BIOS. When the proc goes from an idle state to a load state, it has to lower the voltage pulsing through the core or else too much current would be passing through the chip. Thats called Vdroop; the voltage droops down some to accomodate higher loads.

 

When load is taken OFF of the processor, it returns to its non-loaded voltage state. In a perfect world, that would be the number you set in the BIOS. However, in the world of electronics, its not quite like that. The power regulators on the board cant just switch to a new voltage level; they have to ramp it up, and quick. This causes an overshoot of the target voltage. <-- Thats key to understanding your Vdrop. Its known as "ringback" and if you could see a graph of the realtime voltage levels, it would look almost like one of those heart monitors at a hospital- it pings up then back down and settles at the center line.

 

In the BIOS, you set the maximum voltage. Those ringbacks cannot exceed that voltage. Therefore, since there always will be ringbacks, Intel/AMD/Ted's Processor Manufacturing Emporium/whoever HAS to incorporate a voltage buffer on the chip, which is your Vdrop, or else the chip would overvolt every single time.

 

The reason it COULD be causing your instability is because you might simply not have that maximum (vcore) set high enough, and those vdrops and vdroops bring the core voltage too low and cause instability. Never set your vcore higher than 1.35, as nanoprobe said, but until then you can keep going higher to try and find a stable voltage level. If you cant find a vcore that brings stability to your system, then you either have heat problems, another component is whats causing the instability (RAM or northbridge are possible culprits), or you have reached the max frequency of your particular chip.

 

Good luck!

[phat_cow]

Ehh... maybe, but not in the way you might think. The difference (in your case .0305 volts) is called Vdrop. Not to be confused with Vdroop, which is something else entirely. Vdrop is an Intel thing, designed to protect your chip from over-volting. Vdrop is essentially the voltage buffer from the maximum allowed core voltage, ie the number you set in the BIOS. When the proc goes from an idle state to a load state, it has to lower the voltage pulsing through the core or else too much current would be passing through the chip. Thats called Vdroop; the voltage droops down some to accomodate higher loads.

 

When load is taken OFF of the processor, it returns to its non-loaded voltage state. In a perfect world, that would be the number you set in the BIOS. However, in the world of electronics, its not quite like that. The power regulators on the board cant just switch to a new voltage level; they have to ramp it up, and quick. This causes an overshoot of the target voltage. <-- Thats key to understanding your Vdrop. Its known as "ringback" and if you could see a graph of the realtime voltage levels, it would look almost like one of those heart monitors at a hospital- it pings up then back down and settles at the center line.

 

In the BIOS, you set the maximum voltage. Those ringbacks cannot exceed that voltage. Therefore, since there always will be ringbacks, Intel/AMD/Ted's Processor Manufacturing Emporium/whoever HAS to incorporate a voltage buffer on the chip, which is your Vdrop, or else the chip would overvolt every single time.

 

The reason it COULD be causing your instability is because you might simply not have that maximum (vcore) set high enough, and those vdrops and vdroops bring the core voltage too low and cause instability. Never set your vcore higher than 1.35, as nanoprobe said, but until then you can keep going higher to try and find a stable voltage level. If you cant find a vcore that brings stability to your system, then you either have heat problems, another component is whats causing the instability (RAM or northbridge are possible culprits), or you have reached the max frequency of your particular chip.

 

Good luck!

 

That is an EXCELLENT answer! Thank you very much. I understand what vdrop and vdroop is now.

 

Thanks again!

[El_Capitan]

Just curious, what thermal compound are you using? I am also using the Noctua NH-D14, but with Tim Consultants T-C Grease 0098. If you're hitting 76C on those voltages...

 

I can hit 4.2 GHz without HT on my board (see sig), I need to set my Vcore to 1.36250. Max temp on load is 73C using IntelBurnTest.

 

My current 24/7 settings is 4.1 GHz with HT, my Vcore is set to 1.350. Max temp on load is 71C using IntelBurnTest.

 

My i7 920 d0 is a B batch (didn't write it down). Not as good as other batches out there, but it's nice to know I can hit 4.2 GHz, even though my voltages aren't as low as I'd like them to be.

[nanoprobe]

Just an FYI. If you're cooling with air turning HT off can lower your temps as much as 10-12c. Kinda defeats the purpose of having HT but if heat is an issue and you're looking for a stable OC it's something to consider.

[El_Capitan]

Just an FYI. If you're cooling with air turning HT off can lower your temps as much as 10-12c. Kinda defeats the purpose of having HT but if heat is an issue and you're looking for a stable OC it's something to consider.

I use my Intel system for video editing, so HT's useful. Also FYI, with HT off, you can also set a lower stable Vcore.