Windows 7 on more than 4 cores

I recently built myself a desktop with an intel Core i7 920 processor. The Core i7 is a Quad core processor with HT technology, so the operating system believes it is running on 8 cores. I am running Windows 7 beta build 7000 on it. The following observations are based on the graphs on the performance tab in Windows Task Manager.

I observe that the first four graphs in the Task Manager seem to be doing most of the work on Windows. The last four processors are idle most of the time. The only time I have seen the fifth processor being used even a little bit is when I ran a bunch of programs at the same time (which proves that they are used sometime at least).



My questions are:

1. Is Windows optimized for a maximum of 4 cores?
2. In the case of a quad core processor with HT, how are the graphs in the Task Manager arranged? Do the first four graphs correspond to the physical cores, and the last four graphs to their HT "shadows"? Or is it P1, P1shadow, P2, P2shadow, etc? Because, if it is the second case, then I will get better perf out of Windows by turning off HT.

You're probably seeing the results of Core Parking. Windows 7 will power down cores to save energy when it isn't busy enough to utilize them.

AndyC said:

You're probably seeing the results of Core Parking. Windows 7 will power down cores to save energy when it isn't busy enough to utilize them.

Thanks... it really might be core parking. Just watched the video of Mark Russinovich, and it says that Windows 7 has support for 256 processors (and I have a measly 8), and Core Parking even knows which cores are on the same die so that it can power down the entire socket.. In short, I am now sure Win7 does a great job running on my Core i7

You planning to get some more ram for that machine? Seems a shame to have a quad core CPU but have it be bottlenecked by only 2 GB of  ram.

ManipUni said:

You planning to get some more ram for that machine? Seems a shame to have a quad core CPU but have it be bottlenecked by only 2 GB of  ram.

Well, I really wanted a 32 bit system (so as not to be bugged with driver issues), so I knew my useful limit was 3GB. I thought that systems handle 2-way symmetrical RAM configurations better than assymetric (2GB+1GB) cases. What I did not know was that this particular CPU+Motherboard combo was optimized not only for the dual channel case, but also for the triple-channel case, so ideally I should have got 3GB (1+1+1 GB).

For now, I will postpone getting more RAM till I take the plunge into 64 bit.

sushovande said:

ManipUni said:

*snip*

Well, I really wanted a 32 bit system (so as not to be bugged with driver issues), so I knew my useful limit was 3GB. I thought that systems handle 2-way symmetrical RAM configurations better than assymetric (2GB+1GB) cases. What I did not know was that this particular CPU+Motherboard combo was optimized not only for the dual channel case, but also for the triple-channel case, so ideally I should have got 3GB (1+1+1 GB).

For now, I will postpone getting more RAM till I take the plunge into 64 bit.

Why don't you download 7-zip and let us know what your benchmark result is. (menu Tools -> Benchmark -> Dictionary size 32MB)
My quadcore gets a result of:

Intel Core 2 Extreme 2.6 GHz

CPU Usage	Rating/Usage	Rating
287 %	2151 MIPS	6571 MIPS

sushovande said:

AndyC said:

*snip*

Thanks... it really might be core parking. Just watched the video of Mark Russinovich, and it says that Windows 7 has support for 256 processors (and I have a measly , and Core Parking even knows which cores are on the same die so that it can power down the entire socket.. In short, I am now sure Win7 does a great job running on my Core i7

I assumed it was because the "extra" virtual HT cores can only do work under certain circumstances. They don't work as well as a proper core.

ZippyV said:

sushovande said:

*snip*

Why don't you download 7-zip and let us know what your benchmark result is. (menu Tools -> Benchmark -> Dictionary size 32MB)
My quadcore gets a result of:

Intel Core 2 Extreme 2.6 GHz

CPU Usage	Rating/Usage	Rating
287 %	2151 MIPS	6571 MIPS

7-zip benchmark. What do the columns mean?

CPU Usage                Rating/Usage           Rating
505%                          2180 MIPS                   11013 MIPS

sushovande said:

ZippyV said:

*snip*

7-zip benchmark. What do the columns mean?

CPU Usage                Rating/Usage           Rating
505%                          2180 MIPS                   11013 MIPS

MIPS = Million instructions per second

I don't know what a "rating" is in this context though. I don't use 7-Zip. But I suspect the higher the MIPS the faster it can compress stuff.

PS - Using 7-Zip to benchmark hyper-threading is likely flawed.

After countless programs to test CPU verse real and hyper threads on my i7, All EIGHT cores on WIN7 x64 are real and contribute evenly to speed of a single application asking for 8 ore more threads (not the tread pool).  Excessive locking (kernal time) will slow the hyperthreadsto about 10% with the real threads at 90-100%.

 

A second note, I'm not sure what program you were using to test the cpu, but if it was a .net program using the thread pool, it will only ever get 50% of the total load at that time, due to thread fairness in win7 with .net 4.

QuickC said:

After countless programs to test CPU verse real and hyper threads on my i7, All EIGHT cores on WIN7 x64 are real and contribute evenly to speed of a single application asking for 8 ore more threads (not the tread pool).  Excessive locking (kernal time) will slow the hyperthreadsto about 10% with the real threads at 90-100%.

 

A second note, I'm not sure what program you were using to test the cpu, but if it was a .net program using the thread pool, it will only ever get 50% of the total load at that time, due to thread fairness in win7 with .net 4.

Pretty sure Windows 7 can distinguish HT cores from real cores. Perhaps that is why 4 are unused.

http://www.tomshardware.com/news/windows-hyperthreading-intel-nehalem-atom,7831.html

intelman said:

QuickC said:

*snip*

Pretty sure Windows 7 can distinguish HT cores from real cores. Perhaps that is why 4 are unused.

http://www.tomshardware.com/news/windows-hyperthreading-intel-nehalem-atom,7831.html

WIn 7 is surely tuned for Hyper threading, there is no real and hyper cores however.  Each cpu has two threads of code being feed it.  The cpu then looks for stalls, memory read, FPU process, or and answer from another cpu, when it finds a stall it switches to the other thread of code to keep the cpu 100% filled with instructions.

 

Keep in mind on a 3ghz machine, reading a memory location that isnt in the cpu cache could take 20-100 cycles of the cpu, if the memory has been written to virtual memory it could take 1000-10000 cycles before it can get back to work.

 

Also, before win7, each spoftware thread was tightly coupled to a particula core, that coupling can be loose between to hyper cores.

sushovande said:

ManipUni said:

*snip*

Well, I really wanted a 32 bit system (so as not to be bugged with driver issues), so I knew my useful limit was 3GB. I thought that systems handle 2-way symmetrical RAM configurations better than assymetric (2GB+1GB) cases. What I did not know was that this particular CPU+Motherboard combo was optimized not only for the dual channel case, but also for the triple-channel case, so ideally I should have got 3GB (1+1+1 GB).

For now, I will postpone getting more RAM till I take the plunge into 64 bit.

There aren't really driver issues anymore though.  Plus every OEM that ships Core i7 machines, desktop or laptop is sticking 64-bit Windows on them and I imagine the trend will continue with the Arrandales next year.

blowdart said:

sushovande said:

*snip*

What driver issues? How old is the rest of your hardware?

[This thread is a necro from January]

 

I still see some people struggling with the shift to 64 bit, so I didn't want to take the plunge. For example, a friend of mine wasn't able to get Eclipse working, because her Java was 64-bit but the Eclipse she got was 32-bit. I have seen people have issues with VPN as well, which would have been problematic for me.

sushovande said:

blowdart said:

*snip*

[This thread is a necro from January]

 

I still see some people struggling with the shift to 64 bit, so I didn't want to take the plunge. For example, a friend of mine wasn't able to get Eclipse working, because her Java was 64-bit but the Eclipse she got was 32-bit. I have seen people have issues with VPN as well, which would have been problematic for me.

Take the plunge.  I'm on an AMD 4-core Phenom II @ 3.4 GHz and I frikkin love X64.  I was kind of worried about compatibility with drivers and such, but so far, the only thing that doesn't work well is:

 

Juice: I couldn't find a better podcast program

IOmega's drivers for a terrabyte NAS.  Luckily, Win 7 recognizes the paths natively, so no big loss.

 

 

PS try this solution

 

Start -> Msconfig ................

 

 

unchek ALL