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I was hoping to ask this question in a way that doesn't get me downvoted or labelled as a troll!

I have an imac i7, and a home built pc with a phenom II X4 @ 3.4 Ghz (both with about the same amount of ram). This was a deliberate plan - as I didn't want to pay the extra for intel. I have bought another box set of some dvds and was transcoding them down to ipad format so that I could watch on the train. the Imac is about three times as fast when using the same handbrake profile (as per Frames per second)

As a geek though - I was wondering if anyone could shed any technical specifics on why AMD is slower at 'raw number crunching' type tasks. I have read quite a bit on the internet about it but still haven't really found a succinct explanation. The best that I've gotten to is that AMD have lots of smaller ("narrower") in the processor, where intel has a big, wide, 'superhighway'

I get that intel has a bigger budget, but for as long as I can remember, AMD has been the cost-conscious choice that has lagged behind when it comes to raw number crunching, I guess I'm slightly surprised that they haven't caught up.

Again, this is not a bitch, a moan or a dig, I'm just curious about the specifics.


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This isn't my area of expertise, but I'm willing to bet in this case that the i7 is using some proprietary code paths or extensions that make it way faster at these particular kinds of operations. I know apparently QuickSync is amazingly optimized for transcoding. It doesn't mean they're ALWAYS that far apart. – Shinrai Apr 23 '12 at 20:19
up vote 1 down vote accepted

Without the specifics on the processor in your iMac, it's hard to get specific. But... you need to remember that a hyperthreaded processor is like a dual core processor. Not exactly the same, but similar. Hear me out.

A P4 HT 3.3ghz processor can perform better than a single core 3.3ghz processor where multi-tasking is concerned. Raw number crunching is one of those things where if the Operating system AND the software in question will utilize multi-cores properly, a 4 core HT processor will outperform a 4 core non HT processor.

So... you've got an i7, which is probably at the LEAST a 4 core/8 thread processor, and you are comparing it to a 4 core processor. Well... that's almost like comparing an 8 core processor to a 4 core processor. Again, not exactly like comparing, but almost like comparing.

Here's a Passmark benchmark for that Phenom compared to some other processors. Note, the performance graphs are first, and rating for the $$$$ value is second. As you note, Intel will outperform AMD, but AMD will make a budget before it breaks it.

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interesting - so my intel most likely is behaving like an 8 core machine, but my AMD like the 4 core it purports to be - all because of hyperthreading? – phatmanace Apr 23 '12 at 20:52
All 1st and 2nd generation Core i7 processors are at least 4 core/8 thread processors the highest end of the series are 6 core/12 thread. So, in essence, yes. It is behaving like an 8 core machine. – Bon Gart Apr 23 '12 at 21:06

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