WinRAR in Win7 not fully utilising CPU?

Kaiju · 6 Jan 2010 at 02:00

Windows 7 Ultimate
C2D 4300 @ 3Ghz (stressed, no errors)
2GB OCZ RAM (tested, no errors)
WinRAR (latest version) set to High, even realtime mode, no difference.

It seems WinRAR never uses more than 10-15% of the CPU when unpacking. It's set on high performance too.

MKVmerge also doesn't use more than 10% when muxing.

Other programs like Mediacoder or running my PS3 Media Server to encode movies, however have no problem pumpin' the crap outta my CPU.

Any suggestions, I don't seem to recall WinRAR having this problem?

tntcoder · 6 Jan 2010 at 02:10

Possibly a bottleneck on your hard drives.

Could also just be that the CPU isnt optimized for winrar operations, or vice versa. Either way not much you can do about it

Kaiju · 6 Jan 2010 at 02:14

Ah, I see. I have an ageing old WD Raptor 74GB.

I was looking to invest in a SSD quite soon, so that may help some.

I'm also testing other zipping programs at the moment.

NathanE · 6 Jan 2010 at 09:51

WinRAR is severely limited by I/O performance.

If it is reading from Hard Disk 1 but writing to Hard Disk 2 then you will find performance to be several magnitudes higher.

AbsenceJam · 6 Jan 2010 at 13:31

Muxing and unpacking don't really need much CPU power as you're not calculating anything really so it's disk limited. Encoding is another story.

mrk · 6 Jan 2010 at 13:48

As above, you won't see any CPU usage worth noting during unpacking.

Kaiju · 6 Jan 2010 at 13:51

Right, so due to limited I/O performance the program can't fully utilise the CPU.

Got it, thanks guys.

mrk · 6 Jan 2010 at 13:52

It won't ever tax the CPU during unpacking as this is an area that's disk bearing, not CPU bearing.

Bung an SSD in there and you'll see a big jump in unpacking speed but the CPU will still remain free.

Kaiju · 6 Jan 2010 at 14:15

Cheers man, SSD here I come!

Pho · 6 Jan 2010 at 14:37

Have you tried watching the activity in the 'Reliability and Performance Monitor' whilst unraring? It should show what's bottlenecking.

start > perfmon.msc

Broken Hope · 6 Jan 2010 at 15:05

Go to tools > Benchmark and hardware test. If it maxes out your CPU or close enough then it's working fine. Just most if not all of the multi-threading in WinRAR is for compressing, not unpacking.

AbsenceJam · 6 Jan 2010 at 15:26

Kaiju said:
Cheers man, SSD here I come!

Just do drive>drive and you'll see massive increases. With one disk the heads need to read and then write each piece so they're jumping everywhere, with two disks it's fairly continuous if the files and empty space are contiguous.