Win 8 misinterprets CPU overclock, any actual ramifications?

[KingFatty]

I have an overclocked CPU. My BIOS recognizes the actual overclock, and running CPU-Z under Windows 8 recognizes it too.

But when I bring up the Task Manager (CTRL-Shift-ESC) and select the Performance tab, Windows 8 shows all the CPU information including "Maximum Speed". But the maximum speed Windows 8 reports there does not match the actual overclock that CPU-Z reports. The actual CPU speed does fluctuate, but as reported by windows it remains capped at the artificially low speed.

I'm guessing this is all cosmetic and I can ignore it, but I can't help wondering if the mismatching info is affecting my experience somehow? The issue also may be related to the fact that I've unlocked some cores, so windows also misidentifies my CPU as a different kind than it actually is.

 

[GlacierFreeze]

Just run some benches and compare scores.

 

[Mark R]

The "maximum speed" indication is the "official" maximum speed of the CPU. It doesn't change with the overclock.

The actual speed indication does.

Also worth checking your power profile. Different power profiles ramp the CPU up and down more aggressively.

If you're in power saving profile, the CPU will be throttled back to an artificially low level. If you put it in max performance mode, the CPU will run at close to max speed all the time, even when idle.

 

[KingFatty]

The "maximum speed" indication is the "official" maximum speed of the CPU. It doesn't change with the overclock.

The actual speed indication does.

OK then I have an anomaly.

Your image shows that the actual "speed" indication sensed by windows can match the overclocked speed. The actual speed can exceed the "maximum speed" indication.

My situation is different. The Windows "speed" never exceeds the "maximum speed" indication.

Also, I get a contradiction between Window's "speed" and the current CPU frequency that is overclocked.

Based on your screenshot, I'd assume that your CPU-Z would show 4.34 GHz, matching the Windows speed.

However, mine doesn't do that, they are mismatched?

Using your numbers for example, my CPU-Z would show 4.34 GHz, my Windows maximum speed would show 3.5 GHz, but the "speed" shown by windows would be 3.5 GHz (not 4.34 GHz).

 

[Puppies04]

Is your cpu under stress when you are looking at the "speed" in windows and are you on the high performance power option?

 

[Vectronic]

When I'm at 4.5GHz Win8 usually shows 4.34 or 4.43 for normal applications that are using "100%"... stress tests get a bit closer, 4.46 to 4.49.

Maybe you haven't run anything to go past 3.5GHz? Window seems to actually report a more accurate number in a way... the clock might be 4.5GHz, but it's not actually being "pushed"... Windows sort of calculates GHz + Amps/Watts to determine how "speedy" the CPU is running.

 

[Red Hawk]

The "maximum speed" indication is the "official" maximum speed of the CPU. It doesn't change with the overclock.

The actual speed indication does.


Also worth checking your power profile. Different power profiles ramp the CPU up and down more aggressively.

If you're in power saving profile, the CPU will be throttled back to an artificially low level. If you put it in max performance mode, the CPU will run at close to max speed all the time, even when idle.

Not true. I have Task Manager pulled up right now and it says that my 2500k's maximum speed is 3.9 GHz, which is close enough to the 4 GHz I have it set to in the BIOS.

Anyways, @KingFatty: This may be a fluke with how the "maximum speed" is getting reported to Task Manager without actually effecting performance, or some setting could be wrong. As others have said, the best way to know is to run benchmarks.

 

[Bryf50]

I don't think the number is anything to go by really. On my machine with speedstep and the c-states off the number was still jumping around like mad. CPU-Z showed the speed correctly. I'm convinced that the number is just some sort of estimation. Even on my laptop Windows 8 shows way more variation in cpu speed then CPU-Z and Hwinfo64.

 

[Liquid_Static]

My Windows 8 install claims 4.35 GHz but I'm actually at 4.4 according to BIOS and CPU-Z

 

[JBT]

My Windows 8 install claims 4.35 GHz but I'm actually at 4.4 according to BIOS and CPU-Z

Ditto.

 

[Mark R]

I don't think that either cpu-z or Windows are truly accurate. One issue is that each core can be separately clocked, so they can look run at different speeds depending on individual load. The other is that speed can be adjusted hundreds of times per second.

Windows will have track of all the cores and will show a time and core average, but due to rounding and accounting issues, it tends slightly to underestimate by about 1%. Cpu-z tends to give a snapshot of the fastest running core, not the CPU as a whole.

 

[Lepton87]

I don't think that either cpu-z or Windows are truly accurate. One issue is that each core can be separately clocked, so they can look run at different speeds depending on individual load. The other is that speed can be adjusted hundreds of times per second.

This is incorrect, only Qualcomm's CPUs can do that.

Ever since Qualcomm started doing multi-core designs it has opted to use independent frequency and voltage planes for each core. While all of the A9s in Tegra 3 and both of the Atom cores used in the Z2760 run at the same frequency/voltage, each Krait core in the APQ8060A can run at its own voltage and frequency

http://www.anandtech.com/show/6536/arm-vs-x86-the-real-showdown/2

 

[Red Hawk]

This is incorrect, only Qualcomm's CPUs can do that.



http://www.anandtech.com/show/6536/arm-vs-x86-the-real-showdown/2

Huh? We're talking about desktop CPUs here. They've had the ability to run at different clock speeds and voltages per core for a while now. That's the whole point of technologies like Turbo Boost and Speed Step.

 

[sm625]

The important thing is to find out what speed you are actually running at. Run superpi 1M and post the time.

 

[Lepton87]

Huh? We're talking about desktop CPUs here. They've had the ability to run at different clock speeds and voltages per core for a while now. That's the whole point of technologies like Turbo Boost and Speed Step.

It's the same with desktops. You don't have separate voltage planes for individual cores in desktops. As far as I remember only Phenom 1 could have separate clocks for individual cores but the idea was scraped in Phenom 2.

 

[dqniel]

Huh? We're talking about desktop CPUs here. They've had the ability to run at different clock speeds and voltages per core for a while now. That's the whole point of technologies like Turbo Boost and Speed Step.

From how I understand it, Turbo is a matter of disabling inactive cores by using power gates. The CPU still uses a single power plane. I don't think the cores can have the clockspeed and voltage individually controlled.

 

[KingFatty]

What got me thinking about this is that I pre-ordered Starcraft 2: Heart of the Swarm, which led to my reinstalling Starcraft 2. It seemed that when SC2 auto-detected my settings that the CPU-related settings were defaulted to lower than what I remembered from long ago when I first bought it. Then paranoia set in and I wondered if maybe Win 8 provides some service that apps can call to request CPU performance capabilities, and then rely on Win 8 info to set their default parameters/expectations of the system.

But I think this was just coincidence, and that I bet SC2 has its own routine to assess CPU capabilities, without needing to call any service in Win 8 for that info.

I'll run a CPU benchmark and see how it compares to a similarly overclocked CPU.