Introduction

First of all, I would like to thank our friends at ASUS who provided the CPU sample and Links for providing the rest of hardware used in this review.

Earlier this month Intel made a big leap into the future of microprocessors. With GPU integration into the processor package Intel marks the beginning of a new era for microprocessors, possibly one just as big as the change that AMD made some three years ago with its first Dual-Core Athlon 64 X2 CPU. The "core" race between AMD and Intel is slowing down due to small percentage of multi-threaded applications available to average users today, but all along there was another race underway and the goal is integration and miniaturization. With their new Clarkdale processors Intel is the first one to take this race to the users and take it out of the shadows, but the finish line is still far away and there is much to be done before we can declare the winner, but nevertheless, a new breed of processors is here with all of its hi-tech features... and flaws.

Without doubt you've already heard or read about the new Clarkdale processors, and their onboard integrated "Northbridge" chip combining graphics processor, memory and PCI-E controller, and since it's the first of its kind you'll be hearing about it a lot more in the near future. What Intel has done here is combined the latest, state-of-the art technology processor and combined it with Northbridge logic in one Multi-Chip Module package. Somewhat similar to the Yorkfield Quad Core processors, where two Wolfdale Dual Core cores were put together in a MCM package to create a Quad Core. It worked well in the past, so there is little reason for doubt this time.



Since this is a processor review, over the next few pages you'll find all the technical information, specifications, good and bad things about the new Clarkdale processor. What you will not find is an in depth review of the integrated graphics processor in Clarkdale,, that part of the review was done earlier by W1zzard and you can find it in his review.

Packaging and Contents

For testing we received processor in a tray package, but for the retail market Intel is shipping a boxed CPU with cooler and some basic documentation.

Core i5 661, the new and the old

Now before we start throwing names and numbers, there are couple of things that should be crystal clear to anyone who wants to understand this review content. It would seem that both Intel and AMD (GPU makers not excluded) have a mission in disorienting and confusing its buyers and generally population that like to be "in touch" with current IT technology with their naming schemes. Depending your source of information you can read a couple of different names, all referring to one product, or one two, or product line or... you get the picture. Here's a simple guideline to the meaning of some names in text that will follow:

• Nehalem - name for microprocessor architecture, 45 nm process node
• Bloomfield- microprocessor core codename, based on Nehalem architecture
• Lynnfield - microprocessor core codename, based on Nehalem architecture
• Core i7 900 Series - brand/model/SKU name for processors based on Bloomfieldcore and Nehalem architecture
• Core i7 800 Series - brand/model/SKU name for processors based on Lynnfieldcore and Nehalem architecture
• Core i5 700 Series - brand/model/SKU name for processors based on Lynnfieldcore and Nehalem architecture

• Westmere - name for microprocessor architecture, 32 nm process node
• Clarkdale - microprocessor core codename, based on Westmere architecture
• Gulftown - microprocessor core codename, based on Westmere architecture
• Core i7 980X (not yet released) - brand/model/SKU name for processors based on Gulftown core and Westmere architecture
• Core i5 600 Series - brand/model/SKU name for processors based on Clarkdale core and Westmere architecture
• Core i3 500 Series - brand/model/SKU name for processors based on Clarkdale core and Westmere architecture

In addition to the naming schemes above you should also be familiar with two desktop platform names Intel will be using for next couple of years. Both platforms are named after the pin count of its corresponding processor. The current LGA 1366 platform consists of Core i7 900 Series processors paired with an X58 chipset based motherboard, while the cheaper and less feature packed LGA 1156 platform consists of Core i7 800 and below series processor paired with P55/H5x chipsets. That makes our Core i5 661 test sample LGA 1156 based, and to use all of its features you'd need a H55/H57 chipset based motherboard but it will work just fine on most current P55 based motherboards (check your CPU support list), maybe a BIOS update is required.

If you are to distinguish one Core model from another, the list above is a must-know, with that obstacle out of the way we can finally talk about Westmere, Clarkdale and Core i5 661, which are more or less the same thing but with different meanings. I consider myself leaning on the optimist side, so we'll start of with good points in Core i5 661, and that would be the Clarkdale CPU core.



Clarkdale brings a few technological advances that will affect the market a great deal in the near future. The core is built using Intel's brand new 32 nm process node, second generation high-k metal gate and for the first time Intel is using immersion lithography during die production. For Intel this translates to better yields, smaller core dies and low production costs, and hopefully this means cheaper prices for the average user as well as better performance, power consumption and overclocking results. Intel will be using this new 32 nm process node until 2011 when their 22 nm process node is scheduled to launch, so there is a lot of time to fine tune production, up the frequencies and lower the power consumption.

Clarkdale's CPU core consists of two physical logic cores in one die with both of them supporting Intel's Hyper Threading technology and that makes it "effectively" a Quad Core processor. It reports four cores to Windows and applications, but in reality each core processes up to two threads each, utilizing all of the core's potential and performance. Improvements are noticeable across the board with Hyper Threading, but when dealing with heavily multithreaded and demanding applications four physical cores are always a better choice than two additional software cores. The other part of Clarkdale is the IGP or integrated graphic processor that holds both memory and PCI-E controllers, more on that part later.



Each of the two CPU cores in Clarkdale has 256 KB L2 cache memory and a total of 4 MB L3 shared cache memory. That's half of what Lynnfield has, and a third of what is available on Bloomfield processors. Clarkdale is also missing some key features that made Nehalem architecture so famous: integrated memory controller and PCI-E bus controller. Although they are physically close, and on the same package, performance wise it's almost the same as if they were implemented on the motherboard. The small 32 nm node production and absence of IMC and PCI-E bus controllers make the CPU part quite compact. With a die size of just 81 mm², it is over a third smaller than the Lynnfield core. Clarkdale's 45 nm IGP part adds another 114 mm² of die size, adding up to a total of 195 mm².

As for the architecture of the CPU cores, with some tweaks here and there to accomplish the 32 nm transition, the CPU cores are still based on the same core design used in Intel's first Nehalem processors, apart from smaller cache and the memory controller being dumped off core again. What's new is seven added instructions called AES-NI, all of them used in encryption/decryption tasks. For most users this is of minor importance, but large companies that encrypt every byte written to hard drive will be happy with the new features.



Turbo Boost still plays a big role in Clarkdale processors, overclocking it up to 3.60 GHz and that's a quite a boost for single threaded applications. With medium load on cores, Core i5 661 will work at 3.46 GHz, scaling down to 3.33 GHz once the 87 W TDP is reached. Now, I did play around with the Turbo Boost feature a little, and it started out as a simple experiment but it quickly became obvious that Core i5 661 will almost never work on its stock 3.33 GHz frequency, no matter how much load you put on cores. No complaints from me there.

Like in Nehalem based processors, Turbo Boost in Core i5 661 Westmere based models works on the same principle. Base clock BCLK always stays at 133 MHz which is multiplied by x9 to get ~1.2 GHz for the idle frequency, by x25 to get stock 3.33 GHz and Turbo Boost then kicks in with multipliers of x26 and x27 to get 3.46 GHz and the maximum of 3.60 GHz. Keep in mind that different models will work with different multipliers to get different values. On paper it looks great, but in reality most of the applications and games today know how to use at least two cores, so most of the time you'll be getting 3.46 GHz from Turbo Boost. Still not bad, but it would seem Turbo Boost makes a whole lot of sense with Quad Core processors. You have horsepower (physical cores) when it comes to heavy multithreading and speed (Turbo Boost-ed one/two or three active cores) when it comes to some light threaded applications.

The dark side of Westmere...

Now we're getting to the bad part of Clarkdale processors, which lies just across two CPU cores. Yes, I'm talking about the integrated graphics processor as Intel refers to it. To get a better idea what this chip is, think of the older G45 chipset used on LGA 775 motherboards. It's made in 45 nm, just like the one implemented on Clarkdale, it has the memory controller, a PCI-E bus controller and an integrated graphics processor. Now if you're thinking that's a lot of similarities to the chip that was implemented on Clarkdale, you'd be right on the money. Integrated graphics in Clarkdale is based on same design as the G45 chipsets with addition of two extra execution (shader) units. Both memory controller and PCI-E bus are implemented in the graphics die, and sadly, it's not the same memory controller used in Nehalem processors, rather a tweaked version of the one seen in P45/G45 chipsets with Core 2 processors. Although the memory performance is much improved over Core 2, memory latency will be a big limiting factor for new Clarkdale CPUs, as you will see from tests up ahead. It should also be mentioned that the memory controller supports up to dual-channel DDR3 at 1333 MHz.



A memory architecture optimized for Nehalem/Westmere will arrive next year with Sandy Bridge, along with a new IGP chip as well. Unlike Westmere, Sandy Bridge processors will not come in a MCM package, both IGP with PCI-E bus and IMC will be integrated onto a single die with the CPU cores. Until then, Westmere leaves a bad taste of beta test subject with a strange mix of old and new, good and bad...

Communication between the two chips (IGP and CPU cores) is done via QPI, while the motherboard chipset either P55 or H5x communicates with Clarkdale via older DMI. The graphics core on the other hand has another link to the outside world, called Flexible Display Interface or FDI. It's used to send the video signal to the I/O ports on the back of the motherboard, so if you are to make use of integrated graphics you must pair up Clarkdale with a H55 Express or H57 Express motherboard. Motherboards with P55 chipsets do not support FDI and your graphics core in the processor will just sit there unused, idling, wasting resources and producing heat. The most frustrating part is that the IGP supports power mangement to reduce heat and power output, but Intel enabled those features only for mobile platforms, so if you pair your Core i5 Clarkdale with a P55 motherboard the IGP will probably double the idle power consumption, not to mention add some extra heat waste.



But... there is a bright spot in this darkness and negativity. Look at the picture above and notice how the new platform with Westmere processors looks more much compact and cleaner related to the older LGA 775 Penryn based platform. All the important functions are now located in just one block (processor) while motherboard logic is left in charge with simpler functions like storage and handling input/output device streams. This picture can be taken as a hint to what Intel plans to do with these new processors and where the future of computing is probably heading. Small, compact, quiet platforms, yet powerful enough to satisfy the needs of most users. The true power of Westmere and for that matter future Sandy Bridge processors lies in portable and small form factor computers.

So to sum it all up, Clarkdale on paper is a very strange and intriguing project. It makes use some of the latest and greatest Intel technology in pair with some of the most criticized silicon they have (IGP). You can't do gaming with this processor alone, and if you're going for external graphic performance, wouldn't Core i5 750 be a far better choice? On the other hand, do you really need a $200 chip for a HTPC or office work? Well, only time and benchmarks will answer that question, and there's a whole lot of results on the next couple of pages.

Test Systems

Below you can see the entire list of programs used to test our processors. Most of the tests make good use of multithreading, but just like real-life situations, there are some tests that prefer higher clock frequencies over number of cores or size of L2/L3 cache buffer. Since we will be using Windows 7 64-bit from now on as base for processor benchmarks, some of them are used in 64-bit versions as well.