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Underclocking 2500K on H67 chipset

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a b à CPUs
January 11, 2011 6:43:25 AM

For those curious about options with the clock multiplier with the H67 chipset, I'll post what I'm finding as I mess with my system.

I have an Asus P8H67-M EVO with a i5-2500K with the base 0805 EFI Bios.
I just have the system posting... The first thing I wanted to check was the ability to modify the CPU multiplier in any way.
The good news so far is that there *is* a CPU multiplier setting... and with a 'K' chip, its allowing me to change it from 16 upto
the 'base' multiplier of 33. I haven't loaded an OS to see how this is behaving yet... but that's a good start :) 
Its possible that a non-K chip can also be clocked below its base, so someone can comment on that.

I'll make the assumption that a P67 board has the 'limited overclocking' freedom to go 4 steps above the max turbo freq (although it
may be the base freq) for a locked (non-K) part, and 'full overclocking' freedom upto 57 for a K part.

This should be characteristic for the H67 boards. I'll post what I discover as I have time.

a b à CPUs
January 11, 2011 12:12:24 PM

Buying a k series CPU for a H67 board is probably the dumbest thing you could do. Next time you might want to take your time and read a little on the internet. The info you seek is out there, all over the place.
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January 11, 2011 2:41:37 PM

daship said:
Buying a k series CPU for a H67 board is probably the dumbest thing you could do. Next time you might want to take your time and read a little on the internet. The info you seek is out there, all over the place.

Buying a Phenom II X6 Black Edition for a H67 board might be the dumbest thing you could do... :) 

I could have bought a i5-2400 from NewEgg for $5 *more* than I paid (after tax) for the 2500K, and it would still be on a UPS truck.
I was looking for a 2500T, but they don't seem to be very available. I'm doing a little experiment to see if the 'cheaper' unlocked performance part
can approach the idle/load power usage of an energy efficient CPU... while having the potential to turbo CPU and (wider) GPU frequencies if
short bursts of 'performance' are required.

Not every machine is a game machine. I don't think its that bad a descision.
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January 11, 2011 3:00:26 PM

Actually no, it's not the dumbest thing you could do. If you want graphics performance that is comparable to a discrete graphics card like the HD5450, you need Intel's HD3000 IGP which is only available on K cpus. People who are buying H67 motherboards to utilize the onboard graphics of the cpu, may want HD5450 level performance for an extra 20 dollars without having to add more pci clutter to their computer. Far from dumb.

And yes, not being able to overclock the K cpus so far on the H67 chipset does suck. This is just simply a move by Intel to make more money now and recapture the spotlight from AMD’s Bulldozer by releasing their z68 (or whatever it’s called) chipset later this year. Whether it pays off for Intel is a different question.

JPMUCHA I am interested in your underclocking/overclocking results with the K cpu, please post them :) 
a b à CPUs
January 12, 2011 12:31:52 AM

Thanks. The 12 EU integrated graphics was a factor. Along with a little flexibility/power if I decided to move this CPU into something else in the future.

So far, it appears that the base clock can't be set above the 'rated' speed... although it should turbo up beyond that. How the turbo behaves is a big part of my curiousity.
I have been able to set it down to 2.3 GHz to mimic a 2500T. At either 2.3 or 3.3, it seemed to like to downclock itself (with all the energy savings settings running) to 1.6 GHz.

System is a Asus P8H67-M EVO with a 2500K, 2x2GB of Corsair @1333CL9, 1TB Seagate 7200.12, old IDE DVD reader, powered by a 400W Corsair 80Plus supply.
Note I haven't loaded the updated GPU driver yet (required .NET... installation in progress)

@Base 2.3 GHz (all 4 cores idling at 1.6 GHz during a 107 object Windows update) 0.84 avg core voltage (dynamic). Kill-a-Watt reporting 42-43W for the complete system. One of the cores blipped up to 3.7 GHz ... touched upto 55W at the wall.

That kinda confirms that the turbo is tied to the 'max multiplier'. I'm really impressed so far... Intesting to see the TMonitor and performance grids at work :) 
I'll see what the system does with a 3.3GHz base, but I have a feeling it will idle the same since the system drops to 1.6 GHz.
January 12, 2011 1:36:36 AM

If your focus is to get the lowest idle wattage possible.

Some thoughts:

- See if you can lower the core voltage of the CPU @ 1.6ghz lower than 0.84v

- If you lower the base clock of the HD3000 graphics, you should be able to drop the voltage

- Also there might be a bit of wattage in the RAM by lowering voltage

- If you want to get drastic, replace the 1TB desktop with a 750G laptop drive.


Looks good so far.
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January 12, 2011 2:56:30 PM

CPL123 said:
If your focus is to get the lowest idle wattage possible.

Some thoughts:

- See if you can lower the core voltage of the CPU @ 1.6ghz lower than 0.84v

- If you lower the base clock of the HD3000 graphics, you should be able to drop the voltage

- Also there might be a bit of wattage in the RAM by lowering voltage

- If you want to get drastic, replace the 1TB desktop with a 750G laptop drive.


Looks good so far.

After watching the system a little more, 40W idle is pretty normal. Running a benchmark, it did touch upto 90W with all 4 cores active and 'accelerated'. For running through the Windows Update crap last night... I'd say the system was at idle speeds for roughly 97% of the time... so idle consumption will be key. With the good idle behavior of the 2500K, I'm assuming that the 'value' placed into the 2500T is that its 'energy management circuitry' is designed to stay under the 45W ceiling... while allowing a 1GHz Turbo (from 2.3GHz) ... and actually increased GPU turbo headroom (lower base... higher turbo... less EUs than a 'K').

The initial underclocking effort may be somewhat of a waste, since the processor does such a good job of power gating and underclocking itself. I'll look and see how low it can go be checking out the 2500T voltage specs... that should have some safely reduced voltages. The GPU was going to be my next target. I assume those also get power gated and reduced automatically, so finding a way to influence this will be interesting. RAM is already running at 1.5V (just at stock 1333 now). This box will eventually be a Home file Server, so I'll have 4 or 5 drives in it (which I already have) so dropping laptop drives won't be an option... although a good idea for a new build. I think it roughly works out that 1W turns into $1 if you run that device 24/7 for a year. The 40W idle will save me a ton compared to the old server that idled at over 80W.

Thanks for the tips!
!