How to find the mininum frequency a processor can practically run?

[karthikvm]

Hi All,

I am working on a research project where I am trying to lower the CPU frequency to the practical minimum on certain low priority tasks to save energy. I am using simulation to obtain results.

Intel's Speed Step technology or AMD's Cooln Quiet automatically reduces the frequency when the load on the processor is low. My questions are:
a) How do we get the available frequency range for a given processor? Is this specified in the data sheets?. I am interested in the lowest frequency practically a processor can run.
b) Also like overclocking is there a possibility to practically reduce the frequency of the processor below these standard frequency range?

I need this lowest frequency info for a given processor so that I can set my simulator to run at this frequency. Any help on this regard is highly appreciated.

Thanks,
Karthik

 

[junkeymonkey]

windows may not allow but Linux you could , but I don't know where you would find any specs on how low you can go ?

https://software.intel.com/sites/default/files/comment/1716807/how-to-change-frequency-on-linux-pub.txt

https://wiki.debian.org/HowTo/CpuFrequencyScaling

https://www.kernel.org/doc/Documentation/cpu-freq/governors.txt

my 4670 i5 at idle is 800mhz [????]

don't see anything on AMD cpu's but may be configured the same ?

seemed like my buddy played around with this years ago

 

[Nonpossible]

Hi All,

I am working on a research project where I am trying to lower the CPU frequency to the practical minimum on certain low priority tasks to save energy. I am using simulation to obtain results.

Intel's Speed Step technology or AMD's Cooln Quiet automatically reduces the frequency when the load on the processor is low. My questions are:
a) How do we get the available frequency range for a given processor? Is this specified in the data sheets?. I am interested in the lowest frequency practically a processor can run.
b) Also like overclocking is there a possibility to practically reduce the frequency of the processor below these standard frequency range?

I need this lowest frequency info for a given processor so that I can set my simulator to run at this frequency. Any help on this regard is highly appreciated.

Thanks,
Karthik

If you don't get any answers maybe you could monitor what your CPU drops to while idle and use that as a baseline to work with.
I think you can run the clock speed pretty low and still handle processes, it just depends on HOW smoothly you want to run things.

I'll go see right now if I can under-clock my 3770k.

UPDATE: So I went to my bios, (Gigabyte Z77X-UD5H, BIOS Version F14), and went to the multiplier settings. If I chose any frequency lower than 1.6Ghz, the BIOS would automatically revert back to my last settings, (4.2Ghz).
So, I selected 1.6 Ghz, hit save and restarted my machine. Windows booted like normal, but when I checked my settings using my hardware monitor, it still said it was clocked at 4.2Ghz. So the 1.6Ghz didn't take.

 

[Karadjgne]

My 3570k and 3770k both idle at 1600MHz as set by Intel speedstep. They'll both run background tasks like A/V etc. But that was also possible years ago, like on my P2 350MHz, running Win98SE, using x86 apps, 350MHz was fine, and also did background tasks at idle (no idea the speeds). So just how low you can go isn't as big a question as just what will run at low speeds. Running something like Office or A/V is entirely different than a game. I suppose, technically, you could run Word at 10Hz, but loading a page would take an hour. A web page probably wouldn't run at anything less than 60Hz, that being the speed of the avi's ads and videos etc.

 

[Solandri]

In Windows:

Control Panel -> Hardware and Sound -> Power Options -> select a plan (usually Power Saver, but you can do this to any power plan or create a new one)

Change plan settings -> Advanced power settings

In the pop-up, scroll down to Processor power management. Open Maximum processor state and set it to the minimum (1%). That almost completely turns Speedstep off and your processor will run at its minimum speed. (It's usually 800 MHz if you check it with a CPU monitor.)

Dunno if you can go below these speeds. I would imagine so if your motherboard's base clock speed can be modified down.

 

[Nonpossible]

My 3570k and 3770k both idle at 1600MHz as set by Intel speedstep. They'll both run background tasks like A/V etc. But that was also possible years ago, like on my P2 350MHz, running Win98SE, using x86 apps, 350MHz was fine, and also did background tasks at idle (no idea the speeds). So just how low you can go isn't as big a question as just what will run at low speeds. Running something like Office or A/V is entirely different than a game. I suppose, technically, you could run Word at 10Hz, but loading a page would take an hour. A web page probably wouldn't run at anything less than 60Hz, that being the speed of the avi's ads and videos etc.

That's a good way to explain it.
I really like my 3770K, had it for a little while now. Wife wants the tower gone but no one wants a 3rd Gen i7 I guess. haha.

 

[Nonpossible]

I turned my i7-4700HQ (What I'm currently typing on) down to 800 Mhz. It is kind of painfully slow, but most applications are running okay. The lowest it has gone since I changed it is 712MHz and it maxes at 798Mhz.

 

[Karadjgne]

My i7 was $50 on ebay. Dude typed in a 370k, so I got lucky I found it. Normally those cpus go for $150+. Yes they are still very popular with ppl getting an i7 with @ 80% the power of an i7-7700k. My whole system cost less than $600 and that included a $80 psu and a $280 gpu. I figure it'll be good for several more years at least in gaming, and several more for office/email, web surfing.

 

[MrN1ce9uy]

My i7 was $50 on ebay. Dude typed in a 370k, so I got lucky I found it. Normally those cpus go for $150+. Yes they are still very popular with ppl getting an i7 with @ 80% the power of an i7-7700k. My whole system cost less than $600 and that included a $80 psu and a $280 gpu. I figure it'll be good for several more years at least in gaming, and several more for office/email, web surfing.

And you actually received an i7-3770K for $50? Did the seller not know its value?

 

[Karadjgne]

Guess not. I also did a batch search, to find what batches had reported OC and vcore, and it turns out that this batch has very good results with more than a few hitting 5.1GHz at less than 1.4v and minimum OC of 4.6GHz. I've had this cpu upto 4.9GHz at 1.32v and just haven't bothered pushing it to see exactly how much further I could go. Yeah, he sold me a Gem for the price of dirt lol.

 

[Nigel Spike]

The lowest frequency I can find for a CPU used in a PC is 2 MHz to 3.125 MHz in the 8080. The OP did not state that it had to be a "modern" CPU or platform. The info can be found on https://en.wikipedia.org/wiki/Intel_8080

My earliest experience was the 8088 at 4.77 MHz.

Nigel

 

[Karadjgne]

The lowest frequency used by a pc was 1.108MHz by the Commodore Vic-20. (1981) (PAL) or 1.02MHz (NTSC) .

I had one. New. Used a tape cassette drive to load games. Took 15 minutes to load 'Spaced Invaders' and thats only if there was no glitches, otherwise it meant rewinding the tape and starting all over.

 

[karthikvm]

windows may not allow but Linux you could , but I don't know where you would find any specs on how low you can go ?

https://software.intel.com/sites/default/files/comment/1716807/how-to-change-frequency-on-linux-pub.txt

https://wiki.debian.org/HowTo/CpuFrequencyScaling

https://www.kernel.org/doc/Documentation/cpu-freq/governors.txt

my 4670 i5 at idle is 800mhz [????]

don't see anything on AMD cpu's but may be configured the same ?

seemed like my buddy played around with this years ago

Hello junkeymonkey thank you so much for the pointers. Actually the different frequencies a processor can run is called p states in intel processors. I am looking for the info about the range of these p states for a given processor. It seems that Intel does not share this info in the publicly available docs. Please check this link for more info: https://software.intel.com/en-us/forums/software-tuning-performance-optimization-platform-monitoring/topic/391483

Since I am using the simulator instead of the real processor, I need to specify these values by myself. Hence I cannot use the command line tools to fetch info about the pstates.

 

[karthikvm]

Hi All,

I am working on a research project where I am trying to lower the CPU frequency to the practical minimum on certain low priority tasks to save energy. I am using simulation to obtain results.

Intel's Speed Step technology or AMD's Cooln Quiet automatically reduces the frequency when the load on the processor is low. My questions are:
a) How do we get the available frequency range for a given processor? Is this specified in the data sheets?. I am interested in the lowest frequency practically a processor can run.
b) Also like overclocking is there a possibility to practically reduce the frequency of the processor below these standard frequency range?

I need this lowest frequency info for a given processor so that I can set my simulator to run at this frequency. Any help on this regard is highly appreciated.

Thanks,
Karthik

If you don't get any answers maybe you could monitor what your CPU drops to while idle and use that as a baseline to work with.
I think you can run the clock speed pretty low and still handle processes, it just depends on HOW smoothly you want to run things.

I'll go see right now if I can under-clock my 3770k.

UPDATE: So I went to my bios, (Gigabyte Z77X-UD5H, BIOS Version F14), and went to the multiplier settings. If I chose any frequency lower than 1.6Ghz, the BIOS would automatically revert back to my last settings, (4.2Ghz).
So, I selected 1.6 Ghz, hit save and restarted my machine. Windows booted like normal, but when I checked my settings using my hardware monitor, it still said it was clocked at 4.2Ghz. So the 1.6Ghz didn't take.

Hello Nonpossible, thanks a lot for your inputs. Since I am using a simulator and not a real processor, I need to fix the frequencies by myself. This led me to check about the available frequency range. But it seems that they are not publicly available at-least for intel processors.

 

[karthikvm]

In Windows:

Control Panel -> Hardware and Sound -> Power Options -> select a plan (usually Power Saver, but you can do this to any power plan or create a new one)

Change plan settings -> Advanced power settings

In the pop-up, scroll down to Processor power management. Open Maximum processor state and set it to the minimum (1%). That almost completely turns Speedstep off and your processor will run at its minimum speed. (It's usually 800 MHz if you check it with a CPU monitor.)

Dunno if you can go below these speeds. I would imagine so if your motherboard's base clock speed can be modified down.

Thank you Solandri for your inputs.

 

[karthikvm]

My 3570k and 3770k both idle at 1600MHz as set by Intel speedstep. They'll both run background tasks like A/V etc. But that was also possible years ago, like on my P2 350MHz, running Win98SE, using x86 apps, 350MHz was fine, and also did background tasks at idle (no idea the speeds). So just how low you can go isn't as big a question as just what will run at low speeds. Running something like Office or A/V is entirely different than a game. I suppose, technically, you could run Word at 10Hz, but loading a page would take an hour. A web page probably wouldn't run at anything less than 60Hz, that being the speed of the avi's ads and videos etc.

Thank you Karadjgne for your inputs. What I am looking for is a document specifying the range of frequencies available for a processor. It seems it is not available publicly for intel CPUs.

 

[karthikvm]

The lowest frequency I can find for a CPU used in a PC is 2 MHz to 3.125 MHz in the 8080. The OP did not state that it had to be a "modern" CPU or platform. The info can be found on https://en.wikipedia.org/wiki/Intel_8080

My earliest experience was the 8088 at 4.77 MHz.

Nigel

Thank you Nigel for your pointers. I really do not want to go that early in history . I am simulating Intel Xeon X5550 Gainestown processor. JFYI.

 

[Karadjgne]

Try contacting ark.intel.com and under support, choose processors, then live chat. If anyone knows the range a cpu will run at, or where that info can be found, it'll be Intel itself.

 

[junkeymonkey]

https://software.intel.com/en-us/articles/power-management-states-p-states-c-states-and-package-c-states

 

[Karadjgne]

Seriously convoluted article, it was all over the place. A simple description of C-0 through C-6 would have been good knowledge to start the explanation.
http://www.hardwaresecrets.com/everything-you-need-to-know-about-the-cpu-c-states-power-saving-modes/