super question

[john3850]

SuperPi is single threaded correct
When I ran Super Pi 32m on a i5 at 3800mhz it used all 4 cores at 25% cpu load.
Next I run Super Pi 32m on a i7-930 at 4000mhz and it only uses 1 core at 12% cpu load
The results are close

Why does a i5 use all the cores on a single thead pi.
Better why does the i7-930 only use 1 core at half the cpu load.

 

[GammaLaser]

Still single threaded, all 4 cores may have been in use because the OS was bouncing the app between cores. Overall, 25% CPU usage means only one core was being used at a given instant.

You can try setting task affinity to pin SuperPI down to one core. Also, I think Win7 had some optimizations to keep threads pinned to a core.

 

[tweakboy]

Its a more powerful system duh!

 

[Blastman]

i5-750 has 4 logical processors. 25% is full loading on one processor (1/4 of 100%).

i7-930 has 8 logical processors (4 cores but each core has hyperthreading so each core shows up as 2 logical processors). 12.5% is full loading on one processor of the i7.

 

[Idontcare]

i5-750 has 4 logical processors. 25% is full loading on one processor (1/4 of 100%).

i7-930 has 8 logical processors (4 cores but each core has hyperthreading so each core shows up as 2 logical processors). 12.5% is full loading on one processor of the i7.

^ the answer

 

[Borealis7]

i've always wondered how load% is calculated.
does the CPU report its load or is this purely an OS feature?
obviously the CPU does "know" how much work it has since it switches between power states.

i'm too lazy to google it though...

 

[betasub]

Its a more powerful system duh!

Awe. Another classic from the tweakster...

 

[PlasmaBomb]

i5-750 has 4 logical processors. 25% is full loading on one processor (1/4 of 100%).

i7-930 has 8 logical processors (4 cores but each core has hyperthreading so each core shows up as 2 logical processors). 12.5% is full loading on one processor of the i7.

I was going to write this... but grats to Blastman for the prompt response.

 

[john3850]

i5-750 has 4 logical processors. 25% is full loading on one processor (1/4 of 100%).

i7-930 has 8 logical processors (4 cores but each core has hyperthreading so each core shows up as 2 logical processors). 12.5% is full loading on one processor of the i7.

Load difference solved

 

[VirtualLarry]

i've always wondered how load% is calculated.
does the CPU report its load or is this purely an OS feature?
obviously the CPU does "know" how much work it has since it switches between power states.

i'm too lazy to google it though...

The OS knows how many timeslices it schedules, and reports CPU time appropriately.

 

[john3850]

Why does the i5 use four cores on a single thread Pi.
It seems like a waste of 3 good cores.
Now a i7-Bloomfield is using one core and the other 3 are saving power and ready for something else to use them.

 

[sm625]

I wonder... if you set superpi's affinity to one core, will it run any faster or slower? I especially want to test that on llano, since its turbo is more quirky.

 

[GammaLaser]

Why does the i5 use four cores on a single thread Pi.
It seems like a waste of 3 good cores.
Now a i7-Bloomfield is using one core and the other 3 are saving power and ready for something else to use them.

To expand on my first post above, it's up to the scheduler in the OS to decide where to run the program each time a task switch occurs. Past versions of Windows didn't handle multitasking between cores all that well, but Win7 has new features to improve this, for example see Core Parking: http://blogs.technet.com/b/mattmcspirit/archive/2009/05/07/seeing-core-parking-in-action.aspx. The scheduler may also have optimizations for HyperThreading-enabled processors since performance may differ based on where the tasks are scheduled in relation to the physical cores.

From what I've seen thread bouncing has little impact on performance, but it could possibly interfere with a core's ability to manage its performance/power states thus negatively impacting power consumption.

 

[Tuna-Fish]

i've always wondered how load% is calculated.
does the CPU report its load or is this purely an OS feature?
obviously the CPU does "know" how much work it has since it switches between power states.

How much "work" gets done is entirely irrevant to cpu utilization -- it is simply a measure of how large proportion of the timeslices got assigned to threads. So OS only.

 

[GammaLaser]

i've always wondered how load% is calculated.
does the CPU report its load or is this purely an OS feature?
obviously the CPU does "know" how much work it has since it switches between power states.

i'm too lazy to google it though...

Also, I believe the OS is largely responsible for directing power state management, although the CPU (especially for TurboBoost) can override the OS-requested state based on its own information of die temperature, power dissipation, etc.

 

[john3850]

To expand on my first post above, it's up to the scheduler in the OS to decide where to run the program each time a task switch occurs. Past versions of Windows didn't handle multitasking between cores all that well, but Win7 has new features to improve this, for example see Core Parking: http://blogs.technet.com/b/mattmcspirit/archive/2009/05/07/seeing-core-parking-in-action.aspx. The scheduler may also have optimizations for HyperThreading-enabled processors since performance may differ based on where the tasks are scheduled in relation to the physical cores.

From what I've seen thread bouncing has little impact on performance, but it could possibly interfere with a core's ability to manage its performance/power states thus negatively impacting power consumption.

There was a Registry hack or change that I did to keep all core active and not parked on my 930 when built it.
The HT is always thread bouncing for what ever reason and looks different then regular ht.
Need to do a clean install on the i5 I used a old hd that came from a C2D setup and not used for months.
GammaLaser I get it when I added the ssd i lost my coreparking hack so win 7 is showing less cores being used at times do to the core parking.

Thanks GammaLaser

 

[aigomorla]

u need to set affinity to superpi or it will bounce over all the cores

thats why in OC competitions, they disable active cores to find out which one has the best super pi time.

 

[Plimogz]

Are you saying that different physical cores on the same die, clocked the same, can have differing SuperPi times?

 

[Blastman]

Why does the i5 use four cores on a single thread Pi.
It seems like a waste of 3 good cores.
Now a i7-Bloomfield is using one core and the other 3 are saving power and ready for something else to use them.

Different OS?

 

[Ben90]

thats why in OC competitions, they disable active cores to find out which one has the best super pi time.

Are you saying that different physical cores on the same die, clocked the same, can have differing SuperPi times?

Each core is unique in its overclocking abilities. Core0 might blow nuts and max out at 5ghz while Core3 can hit 5.5ghz within the same parameters. Since a processor can only overclock as fast as its weakest link, disabling all cores but the fastest yields the best overclock.

I haven't been involved with the most recent superpi optimizations for quite some time now. Does it perform best on a single core with all that cache to itself or on a dual setup to offload some of the OS functions?

 

[john3850]

u need to set affinity to superpi or it will bounce over all the cores

thats why in OC competitions, they disable active cores to find out which one has the best super pi time.

I set affinity in superpi for 1 core now things are normal in Pi with both cpus.

The i5 bounces all the cores.
The 1366 seems to do very little bouncing.

I only used Pi to put a load on system to check the vcore.

 

[Blastman]

The reason I asked about the OS the i5/i7 are running on is that the thread scheduler on Windows 7 was updated from that of Windows XP.

informationweek … Microsoft's forthcoming Windows 7 operating system offers improved support for hyper-threading, according to a company official. Bill Veghte, Microsoft's senior VP for Windows development, said the software maker has been working closely with chipmaker Intel to bolster Windows 7's ability to get the most from hyper-threading -- an architecture where processing is divvied up among multiple processors or cores.

 

[john3850]

The reason I asked about the OS the i5/i7 are running on is that the thread scheduler on Windows 7 was updated from that of Windows XP.

Sorry for no answer
Both systems were set up from the same win 7-64oem builders 3 pack.

When i set up the 930 I spent a week getting to a 8.90 1m Pi@4430mhz.
So i spent some time watching the scheduler.
Also used TMonitor for a while and TMonitor responds differently.
Now that same scheduler acts different on a sb.
I would say the scheduler could use a update for sb