The difference between Intel I5 and I7 CPU

[Torrie the Whaler]

Hi,

I was recently told that the I5 cpu were out performing the I7 cpu and considering the cost difference, it would be substantial because I am considering building a new computer.
I thought the I5 chips were inferior I7 chips, something like the celeron used to be.

Any opinion would help,

[photon]

i5 vs. i7 isn't quite as big a difference as Core 2 and Celeron were. Basically the i5 uses dual channel instead of triple-channel that most i7's use.. it makes a significant difference on memory benchmarks, but in the real world the difference won't be massive.

Not all i5 processors support hyper-threading either, which will impact multi-threaded apps somewhat.

I think the i7 also can automatically overclock some of its cores if the other ones are unused, giving a performance boost for single threaded apps and games.

So while the i5 is inferior to the i7, I wouldn't call it Celeron level, there's the i3 for that

[psicodude]

Here are some benchmarks done by Tom's Hardware: http://www.tomshardware.com/charts/2...hmarks,60.html

They benchmark across a wide variety of applications and games, so it should give you a pretty good idea. This chart is a few months old, however.

Just looking at the Far Cry test, frames per second only go up by 5 moving from the i5 to the i7. Is that worth the extra money? It depends on who you are I guess.

[FanIn80]

Originally Posted by psicodude

It depends on who you are I guess.

...or, more importantly, it depends on what you're doing with it.

[psicodude]

Originally Posted by FanIn80

...or, more importantly, it depends on what you're doing with it.

That's what I get for typing a post while listening to someone sitting in my office.

[BaconGuy]

I think if you want to try to futureproof yourself (if there is such a thing), the i7 is the way to go. In the future you will see more software take advantage of 4 cores where as today, most games/software take advantage of two.

The i5 is able to run at higher clock speeds in most cases for single threaded apps. So if you are using older software you will probably see it very close if not outperform an i7. However most software developed today is starting to take advantage of multi-threading. The more threads, the more you will see the performance gain of the i7

[keratosis]

Another thing I believe, is one uses 45nm. and the other is 32nm.
So I5's will run cooler, if that's important to you.

[Torrie the Whaler]

Thanks for all your help!

[FanIn80]

I can't believe no one mentioned the cores yet. While I'm not completely sure of the ramifications, the i7 registers as having 8 cores in Windows while the i5 is only 4. I know 4 of those 8 cores are supposed to be virtual, but I'm sure someone else here can explain it better than I can.

Also, the i7 will use dormant cores to overclock itself on the fly. There's no way it gets outperformed by an i5, unless it's in a very specific setting. I'm willing to bet whoever told you that was probably just looking at the i5's higher GHz rating and extrapolating from there.

Edit: As an example of the overclocking feature, my 1.6GHz i7 will use unused cores to overclock itself to 2.8GHz on the fly. That's the low-end i7, too.

[photon]

Yeah the 4 vs 8 cores is the hyper-threading that I mentioned above. This actually doesn't mean the i7 4 core processor has 8 cores, it just shows up that way under Windows. Hyper-threading means that each physical core can process 2 threads (think two programs, not accurate, but gets the idea) at once. Of course the core can't actually do that, but what it does is mesh the instructions from each program together into one stream and the core works on that stream. Think of a zipper with the teeth being chunks of instructions from a program, often there's gaps in the instructions while it waits for other things to happen, etc, so hyper-threading meshes two together.

Basically it doesn't make a core more powerful, but it does allow it to be more efficient, processing two different threads of instructions without having to go through the kind of overhead normally associated with switching back and forth between 2 different tasks.

So will the hyper-threaded enabled cpu with 8 apparent cores outperform the same one but only with 4 apparent cores? It should under heavy loads and in specific circumstances, but it's going to be a small gain (percentage points), not a huge gain that would be implied by seeing 8 cores vs 4 cores in the process explorer.

As for the turbo boost feature (where processor will overclock one core while the others are dormant) the i5 has that feature as well.

You are right that an i5 won't outperform an i7 in most cases (in a single threaded application that is highly GHz dependent it might if the i5 has a higher GHz rating), but I expect that that wasn't really what the guy he was talking to said, maybe more along the lines that the i5 might be a better cost for performance ratio (it's a little slower, but a lot cheaper kind of thing).

Or maybe they had overclocking in mind, I don't know specifics because I haven't kept up with current processors, but with the newer i5's being 32nm it wouldn't surprise me if you could spend less on an i5 and overclock it a lot to outperform some stock i7's; that's happened plenty of times in the past.

[FanIn80]

Ah... That makes a lot of sense. Thanks for posting that. I knew I was on the right track, I just wasn't sure how everything worked out.

[photon]

My job here is done.

/supernerd away