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I'm shopping for a new laptop from Dell (going to install Ubuntu on it) and I'm currently trying to sort out which processor I want.

Based purely on the clock speed, it would seem that the core i5 is better than the core i7.

The Intel® Core™ i5-430M has a 2.26GHz clock speed, while the Intel® Core™ i7-720QM Quad Core Processor only has a 1.6GHz clock speed. Would this not indicate that the i5 is faster than the i7?

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The difference between i5 and i7 is mostly in integrated graphics isn't it? – Ivo Flipse Mar 25 '10 at 21:26

No, the Megahertz Myth shows how clock-speed comparisons only work within the same range of processors - beyond that, there are too many other changable variables. The i5 is the "budget" version in the i* range, so if you really, really need the extra power (And, indeed, extra power draw) go for the i7, not the i5. (More cores on an i7, and I don't believe the i5s do turbo boost, which overclocks one core while downclocking the rest, for single-threaded CPU hungry applications)

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@Phoshi, I think @Kirk Broadhurst has a point about the i3 being the budget core of the line... – studiohack Mar 25 '10 at 21:59
    
@studiohack23: Oh. Well, I completely missed that being released! Thanks for the update. – Phoshi Mar 26 '10 at 15:03

The i3 is the budget version in the new range. The i5 is the mid-range option, and the i7 is the high performance line. Therefore I'd expect midrange performance, but from a fairly new line the midrange performance is expected to be quite good.

When trying to compare processors I normally look at http://www.cpubenchmark.net/ - it nicely packs everything into one index which can be compared. Certain architectures (and therefore certain product lines and models) suit certain applications more than others, but generally a higher number means more power and can be compared in a fairly linear manner.

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I really like the CPU benchmarks at Passmark.Com

They show a nice rating of CPUs so that you can compare between CPUs or Video Cards and get a good idea of the relative performance of the chips. This allows you to decide if the extra cost is worth the incremental performance.

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Intel's newer chips use a lower base frequency that is then automatically increased using Turbo Boost when only one or two of the cores are being used. This comparison shows that the i7-720QM is faster with a Max Turbo Frequency of 2.8 GHz vs 2.533 GHz. Not to mention it can run twice as many threads and has VT-D and Trusted Execution capabilities. The main benefit for the i5 would be a lower power envelope (longer battery) and an integrated graphics controller (higher graphics memory bandwidth).

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