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swiftcoder

Phenom X4 vs i7-975

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swiftcoder    18437
This is a purely academic question as a) I already have a quad-core Phenom II, and b) there is no way I could afford an i7-975. However, this question has been on my mind for some time. What exactly makes a quad-core, 3.3 GHz i7-975 five times better than a quad-core, 3.4 GHz Phenom II X4?
  • Both are quad-core, both are 64-bit, both are manufactured on a 45nm process.
  • The AMD is clocked fractionally higher.
  • The AMD draws fractionally less power.
  • The AMD has twice as much L2 cache, though only 3/4 the L3 cache.
  • The Intel has hyper threading, which the AMD does not.
  • The AMD costs less than $200, while the Intel costs just under $1,000.
Now, I appreciate that hyper threading can represent close to a 2x performance benefit (though only under very specific conditions), but even so, how is the 5x price premium justifiable? Also, I picked these two because they are their manufacturer's respective top-of-the-line, but one could equally well ask the same about the i7-975 vs the 3.0 GHz Core 2 Quad, which retails for all of $330.

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Fiddler    860
Quote:
Now, I appreciate that hyper threading can represent close to a 2x performance benefit (though only under very specific conditions)


Wait, when does hyperthreading result in a 2x performance increase? Linky? I was under the impression that the improvement would typically be under 10%, due to better pipelining.

Also, the i7 is certainly worth the 5x markup over the Phenom 2. It's faster, sometimes significantly so (50% IIRC) but certainly not worth the premium. On the other hand, the highest end stuff has always been exponentially pricier than what the average buyer would (should) be willing to pay.

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swiftcoder    18437
Quote:
Original post by Fiddler
Quote:
Now, I appreciate that hyper threading can represent close to a 2x performance benefit (though only under very specific conditions)
Wait, when does hyperthreading result in a 2x performance increase? Linky? I was under the impression that the improvement would typically be under 10%, due to better pipelining.
You are correct. I was working from an older document that contained incorrect information (better overview here).
Quote:
Also, the i7 is certainly worth the 5x markup over the Phenom 2. It's faster, sometimes significantly so (50% IIRC) but certainly not worth the premium.
The benchmarks I glanced at seem to suggest a 25-35% speedup. That is still a pretty beefy margin, but not anywhere close to 5x the price.
Quote:
On the other hand, the highest end stuff has always been exponentially pricier than what the average buyer would (should) be willing to pay.
Except in some other areas it doesn't seem to work that way. For instance, between the top-of-the-range video cards right now, the Radeon 5970 benchmarks ~45% faster on average than the GTX 295, but only costs 25% more.

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LilBudyWizer    491
That's kind of funny if you think about it. You don't have to earn much for a 25% boost to income to be worth $800. Particularly if you have no practical way to use a second machine to boost your productivity, i.e. what you're doing demands your full attention and concentration. It's an irrelevant question when it comes to recreation. That isn't a rational decision, that's pure emotion. Some people think it's worth $100k for an RV to set around a parking lot waiting for a football game to begin.

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Hodgman    51339
Quote:
Original post by Fiddler
Wait, when does hyperthreading result in a 2x performance increase?.
You could probably construct an artificial benchmark where every single instruction is a cache-miss, where hyperthreading might allow 2x as many instructions to be in flight at once... Not in real code though ;)

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