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Intel Core i5 Processor Series

The highly diverse mid-end lineup.

December 20, 2010



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Our previous review was dedicated to the Core i7-800 LGA1156 series. The conclusion was that those solutions, as well as the Core i7-900 LGA1366 series, can offer enough computing power for most tasks you may need accomplished. At least four cores and eight threads, clock rates over 3GHz in most cases, at least 8MB of L3 cache — everything the industry has to offer to the mainstream segment. But there was also a downside: the price of about $300 and more.

What should you do if you don't have or aren't willing to spend such money? Say, if you have about $150-250? Obviously, you'll have to compromise, e.g. choose Core i5 instead of Core i7 (if you need an Intel CPU, that is). But there are a lot of Core i5 processors in the market. How do they perform? We'll see in this review.

Testbeds


CPU Core i5-650/655K Core i5-660/661 Core i5-670 Core i5-680 Core i5-750 Core i5-760
Core Clarkdale Clarkdale Clarkdale Clarkdale Lynnfield Lynnfield
Process technology, nm 32/45 32/45 32/45 32/45 45 45
Core clock rate (std/max), GHz 3.2/3.47 3.33/3.6 3.47/3.7 3.6/3.87 2.66/3.2 2.8/3.33
Initial multiplier 24 25 26 27 20 21
Turbo Boost scheme 2-1 2-1 2-1 2-1 4-4-1-1 4-4-1-1
Cores/HT threads 2/4 2/4 2/4 2/4 4/4 4/4
L1 cache, I/D, KB 32/32 32/32 32/32 32/32 32/32 32/32
L2 cache, KB 2x256 2x256 2x256 2x256 4x256 4x256
L3 cache, KB 4096 4096 4096 4096 8192 8192
Uncore clock, GHz 2.4 2.4 2.4 2.4 2.13 2.13
RAM 2xDDR3-1333
Graphics core clock, MHz 733 733/900 733 733 - -
Socket LGA1156
TDP, W 73 73/87 73 73 95 95
Price Newegg, Amazon Newegg, Amazon Newegg, Amazon Newegg, Amazon Newegg, Amazon Newegg, Amazon

Let's start examining the table from the right, because even a glance is enough to understand that the entire family is divided into two different series. According to the rating, the high-end is represented by Core i5-700, of which there are two (and a low-power model — a matter of a dedicated review). Like Core i7-800 processors, both are based on the Lynnfield core. The vital difference is that these Core i5 CPUs don't support Hyper-Threading. The minor differences include lower uncore clock rate (2.13 GHz; like that of the non-extreme Core i7-900 models), lower clock rates and the less aggressive Boost mode.

The left part of the table accommodates Core i5-600 processors, which differ a lot from the 700 and 800 series. Firstly, they only have two cores and support Hyper-Threading to have four threads. Secondly, they just have 4MB of L3 cache, although it works at the same clock rate the Core i7-800's L3 cache does. In terms of performance they are the slowest of the bunch, because they have a different memory controller as well: it's actually not built-in, it's just placed under the same cover. And it's also slower. On the other hand, such a 45nm die also accomodates a GMA HD graphics core that provides enough performance for all but gamers. The computing cores and cache are located in a 32nm die that allows to reduce power consumption despite high clock rates.

As a matter of fact, the Core i5-600 series is diverse as well. For example, the Core i5-650 keeps aloof as the cheapest in the series, a device that may be considered universal. There's sense in purchasing it whether you will use integrated graphics or not. In turn, the Core i5-660 that's priced like Core i5-750, and especially the Core i5-670/680 which are on the level of Core i7 are hardly universal. A priori, judging by specifications (and the results of past tests), these solutions look less attractive than their direct competitors. These models may be interesting, if you're going to use their integrated graphics, something higher-end models lack.

However, graphics performance may differ, so Intel released another isolated model, Core i5-661. It's priced similarly to Core i5-660, but offers higher graphics core clock rates (and performance). On the downside, it lacks VT-d and TXT support and has higher TDP. The resulting solution is a kind of Mini-ITX home theater processor, while the original Core i5-660 is more of an enterprise model. Anyway, these CPUs offer identical performance with a discrete graphics card, so we've taken advantage of it.

The Core i5-655K is yet another isolated solution. It performs like a regular Core i5-650 in the typical mode, but it costs more because of unlocked multipliers. By the way, this time Intel went further than it had done with Core i7-875K and added memory multiplier 12, 14 and 16, offering clock rates of up to DDR3-2133 in the "almost typical" mode. This even surpasses the DDR3-2000 of Core i7-980X without uncore overclocking. All of this makes Core i5-655K an interesting solution for enthusiasts. However, as we mostly test processors in the typical mode, deviating from the test method only to check certain assumptions, we consider Core i5-650/655K as the same — like most users do anyway.


CPU Core i7-860 Phenom II X4 970 Phenom II X6 1055T
Core Lynnfield Deneb Thuban
Process technology, nm 45 45 45
Core clock rate (std/max), GHz 2.8/3.46 3.5 2.8/3.3
Initial multiplier 21 17/5 14
Turbo Boost scheme 5-4-1-1 - -
Cores (HT threads) 4/8 4/4 6/6
L1 cache, I/D, KB 32/32 64/64 64/64
L2 cache, KB 4x256 4x512 6x512
L3 cache, KB 8192 6144 6144
Uncore clock, GHz 2.4 2.0 2.0
RAM 2xDDR3-1333 2xDDR3-1333 2xDDR3-1333
QPI/HT 4.8 GT/s 2000 MHz 2000 MHz
Socket LGA1156 AM3 AM3
TDP, W 95 125 95/125
Price Newegg, Amazon Newegg, Amazon Newegg, Amazon

This time we selected three processors as competitors. The first is the Core i7-860, having the same initial clock rate and the same four cores as the Core i5-760. Although we have already mentioned that it has higher uncore clock rate, a more aggressive boost mode and, most importantly, Hyper-Threading support. By the way, its wholesale price is same as that of the Core i5-670 — another reason to add this CPU to the comparison. The other two rivals are made by AMD. As you may have expected, the more we descend along Intel's processor series, the fiercer becomes the competition between the two companies. Today, AMD has two models in the same price range: Phenom II X4 970 (although other processors in this series can also compete with Core i5 in terms of pricing and performance) and the junior hexacore solution Phenom II X6 1055T.

Another interesting fact is that despite the relative cheapness of processors we're reviewing today, there are as many as three record breakers:

  1. AMD Phenom II X6 1055T — the most affordable hexacore CPU sold for about $200.
  2. AMD Phenom II X4 970 — the highest-clock-rate desktop quad-core solution, 3.5GHz with all cores under load (only Xeon X5677 in the boost mode has higher clock rate).
  3. Intel Core i5-680 — the highest-clock-rate x86 processor. The initial frequency is 3.6GHz and the boosted frequency is 3.86GHz with one core under load. This is even higher than the clock rate of the senior mass-produced Pentium 4, given that the second Core generation is much more efficient. Just 133MHz separates it from the great threshold of 4GHz.

It will be interesting to see how these records manifest themselves in real life.


  Motherboard RAM
LGA1156 Gigabyte P55A-UD6 (P55) Kingston KVR1333D3N9K3/6G (2x1333; 9-9-9-24)
AM3 Gigabyte 890FXA-UD7 (AMD 890FX) Corsair CM3X2G1600C9DHX (2x1333; 7-7-7-20-1T, unganged Mode)


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Article navigation:

Page 1: Introduction, testbeds

Page 2: Tests

Page 3: Tests cont'd, conclusions



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