WinRAR vs. Core Parking vs. Core i7 in Windows 7 and Windows 8
Kapitoly článků
What happens when you run WinRAR benchmark on Windows 7 in a system with Core i7? Windows 7 uses only 6 threads for a reason not know to us yet. We wrote about that almost two years ago when we tested Core i7 980X aka first 6-core Nehalem.
On the seventh page we mentioned something like that:
Core Parking is responsible for as little as possible core utilization if the application does not need that (i.e. not to utilize all cores with low load, but to utilize less cores with higher load). The implementation is anyhow odd and with WinRAR it is very well seen, because it's an application that is far from utilizing all cores at full load, while the relatively low load is quite stable.
So WinRAR was able to utilize only six of twelve available processor threads due to enabled Core Parking. The same behavior is visible with quad core Core i7, even with the detail that the system gives WinRAR also six threads, but now from only eight available. In other words: one core can be completely unused. The thing is that Core Parking in Windows 7 primarily parks threads, not cores, i.e. although WinRAR uses all cores, there are only two cores loaded including Hyper-Threading. From the Core Parking perspective that behavior is not really correct because the primary reason for Core Parking is to save energy by leaving unused cores in low power state (which is not the case with Windows 7 and Core i7).
When we disabled Core Parking, the operating system provided the WinRAR all available threads. Performance increased by 35% in case of 6-core Core i7 980X using WinRAR 2.91 and by almost 40% in case of 4-core Core i7-2600K using WinRAR 4.10 beta 1 (there is noticeable improvement in WinRAR development over the time).
There is nothing easier than to put all relevant numbers in a chart:
AMD FX-8150 (4,20 / 3,90 GHz) | Single-thread | ![]() |
Multi-thread | ![]() | |
Intel Core i7 2600K (3,80 / 3,50 GHz) Core Parking ON | Single-thread | ![]() |
Multi-thread | ![]() | |
Intel Core i7 2600K (3,80 / 3,50 GHz) Core Parking OFF | Single-thread | ![]() |
Multi-thread | ![]() | |
Intel Core i7 870 (3,60 / 3,46 GHz) Core Parking ON | Single-thread | ![]() |
Multi-thread | ![]() | |
Intel Core i7 870 (3,60 / 3,46 GHz) Core Parking OFF | Single-thread | ![]() |
Multi-thread | ![]() |
You can clearly see that WinRAR performs much better on Core i7 with Core Parking disabled. To be honest, we don't know why we forgot about the influence of Core Parking when we made our first Bulldozer review, especially in connection to the fact that we demonstrated it almost two years ago (the way of disabling Core Parking in Windows 7 i either way documented in the internet since the year 2009). We would like to thank to our reader (hladis) who sent us an email about it just after the publication of our first Bulldozer review. We also apologize for missing that „bug“ (really, we shouldn't miss that).