Windows 7 on more than 4 cores | The Coffeehouse

sushovande
Smiley Face Sharp

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.

AndyC

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.

sushovande
Smiley Face Sharp

In reply to AndyC

#Jan 18th @ 1:31 AM

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 Smiley

ManipUni
Proving QQ for 5 years!

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.

sushovande
Smiley Face Sharp

In reply to ManipUni

#Jan 18th @ 3:09 AM

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.

ZippyV
Fired Up

In reply to sushovande

#Jan 18th @ 3:20 AM

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

W3bbo
The Master of Baiters

In reply to sushovande

#Jan 18th @ 2:40 AM

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.

sushovande
Smiley Face Sharp

In reply to ZippyV

#Jan 18th @ 5:40 AM

7-zip benchmark. What do the columns mean?

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

ManipUni
Proving QQ for 5 years!

In reply to sushovande

#Jan 18th @ 10:24 AM

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.

Ion Todirel
buuu

In reply to sushovande

#Jan 18th @ 2:40 AM

if I remember correctly all 4 cores of the i7 are on the same die, comparing to the Core 2 of which 2 or 4 cores (of the 4, 8 cores respectively) are on separate dies?