• Competitor rules

    Please remember that any mention of competitors, hinting at competitors or offering to provide details of competitors will result in an account suspension. The full rules can be found under the 'Terms and Rules' link in the bottom right corner of your screen. Just don't mention competitors in any way, shape or form and you'll be OK.

Hyperthreading and i5?

Auraomega

Auraomega

Auraomega

Associate
Joined
22 Sep 2009
Posts
2,085
Location
Leicester
I've just read somewhere that the i5 doesn't support hyperthreading, which at first seemed like a "uh oh, got to change my parts list again", however I'm wondering if theres any geniune improvement with hyperthreading? From what I know about hyperthreading, running 2 threads on a core with hyperthreading is going to be the same as running 2 threads on a core without, but obviously that would just be silly so I was wondering if someone could explain the benifits AND prove it to me AND advise me on if getting the i7 over the i5 would be a waste for me?
 
Hyperthreading adds a extra logical core to every phisical one to make the usage level of CPU higher. In reality it brings up to 10% increase of speed for well optimized applications. Application with just 2 threads will run exactly the same as it would run on 2 cores without HT.
 
Ok thanks, I understand the basic concept but I never understand how a single physical core running 2 threads is any worse off than a single physical core emulating 2 cores running 2 threads :p

Overall though, the likelyhood of applications using 8 cores plus the minor increase doesn't make the money increase worth it in my eyes.
 
The performance gain from the extra HT cores can be very varied - but it deffinatly can make the desktop a bit smoother and speedier when multi tasking - specially if you've got a couple of multi thread capable apps hammering away...

If you were running something like folding over all 8 cores you'd prolly see speed gains of around 50% or so... same often with things like media encoding where gains of upto 50% can be quite common but in other cases you might not see much more than 10-20% gains.
 
It all depends on what code do you use - because all hyperthreading does is it uses the normally unused resources in the core - usually because of unused predicted conditional parts of the code and such. 50% speedup is a little bit way too optimistic number Rroff. It can happen only with code which is very conditional with many "trashed" code paths...
 
http://www.hardwarecanucks.com/foru...re-i5-750-core-i7-870-processor-review-8.html

56508178.jpg


man, that even convinced me to sell the 750 and get a 860 lol

edit: very nice and informative review
 
Last edited:
Fair play. I'm running a processor with it turned off, as I'd rather run a two core application on two physical cores than two threads on one core. Sadly said application just ignores all further cores.
 
JonJ678 said:
Fair play. I'm running a processor with it turned off, as I'd rather run a two core application on two physical cores than two threads on one core. Sadly said application just ignores all further cores.
Click to expand...

so with hyper threading enabled you get a performance decrease???

i cant see that happening
 
faugusztin said:
It all depends on what code do you use - because all hyperthreading does is it uses the normally unused resources in the core - usually because of unused predicted conditional parts of the code and such. 50% speedup is a little bit way too optimistic number Rroff. It can happen only with code which is very conditional with many "trashed" code paths...
Click to expand...

Well I don't have a massive amount of experience with the i7 and hyper threading - but on my old P4 using hyper threading was good for a 50% boost in workload running things like SETI, folding, etc. and 30-50% framerate boosts in the few games like COD2 that supported multi threaded rendering. I do a lot of video game map compiling and that would happily speed things up by 30-50% and in a very few cases even halve the time it took to compile a map... or I could limit the map compiler to one thread and still have a perfectly smooth and usable desktop.

With 4 physical cores you won't see as big an increase unless your doing something that really thrashes the cores tho as its rare in multi threaded software these days to max out more than one thread with only light to medium usage on teh rest.
 
Ok thanks guys, I've decided that I'll stick with an i5, paying more out for an i7 seems pointless to me, the increase gained in fps is marginally improved (or actually decreased in Far Cry :eek:), and Rroff hit the nail on the head by mentioning the lack of apps/games that fully load 4 cores. i5/1156 should be fine for me I reckon, and compiling anything large normally gets done overnight or while I'm busy elsewhere so the improvements wouldn't really get noticed.
 
JonJ678 said:
Fair play. I'm running a processor with it turned off, as I'd rather run a two core application on two physical cores than two threads on one core. Sadly said application just ignores all further cores.
Click to expand...

Arnt the physical cores 0-3 and the virtual cores 4-7, specifically to encorage the OS to use the real cores first... I also understand that vista and windows 7 can recognise real or virtual cores, and schedule accordingly.

Finally you can always force an application with a set affinity, so that it will run on whichever core you insist on. There are several set affinity applications which can save preferences on a per program basis, so you dont have to bother to remember to do it manually.

Hyperthreading on P4 gave 10-15% boost in many cases, I7's Hyperthreading is better as it has a 4 issue core to play with instead of a 3 issue core. 10-35% gain can be expected on a multithreaded application, or when heavily multitasking, otherwise 0 for single threaded apps running standalone.
 
I think vista copes with it sensibly but XP doesn't. I'll report back if I bother benchmarking with it on and off, but life is probably too short. Currently I just have my subjective opinion, you may well be right.

I've seen it on here that someone was having trouble with games insisting on running on one physical and one virtual, but he wasn't me. I wasn't aware that you could save it on a per program basis, this flattens my reason to turn it off even if I'm right about it using a virtual core.

I much appreciate your input Corasik, I'll google how to do this. Thank you
 
How much difference dose AMDs HyperTransport make and is it better then Intells Hyperthreading i ask due to my next upgrade will be my E6600 to an Phenom 2 x4
 
Last edited:
I had a few of the old Pentium Northwoods/Prescotts and really found HT most useful when encoding video (which I do quite a bit off), so when it was supported in the 1156/860 had no problem choosing it over the 750...
 
You must log in or register to reply here.
Back
Top Bottom