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Clarkdale: Engineering Smarts Behind Marketing’s Mess

Intel Core i5-661: Clarkdale Rings The Death Knell Of Core 2
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The crazy thing is that there’s a ton of intelligence behind Clarkdale, and much of it can be summarized with one word: integration. You see, the entire lineup of Clarkdale CPUs employs two die on a single package. One die consists of the actual processor (32nm), while the other sports a graphics core, integrated memory controller, and PCI Express controller (45nm).

This is, of course, Intel’s first introduction based on its 32nm high-k / metal gate transistor process technology, bringing with it the power and thermal benefits expected from a well-executed transition from 45nm manufacturing. According to Intel, improvements from its first generation of high-k / metal gate transistors include a reduction in oxide thickness from 1nm to .9nm, with gate length dropping to 30nm. As a result, transistor performance increases by more than 22%. Meanwhile, the TDP for all Clarkdale-based desktop processors is 73W, except for the Core i5-661 rated at 87W.

All of the Clarkdale-based Core i5, Core i3, and Pentium processors are dual-core models with 32KB of L1 data cache and 32KB of L1 instruction cache per core, 256KB of L2 cache per core, and up to 4MB of shared L3 cache. This is decidedly a descendant of the Nehalem architecture, which was designed from the get-go for modularity. We'll see that flexibility expand in the other direction in Q1 of this year with Gulftown (six-core, 32nm) and Nehalem-EX (eight-core, 45nm).

The 32nm processor die communicates across a multi-chip package interface, which we’ve had described to us as a very QPI-like bus. And while Intel isn’t talking about the specifications of that inner-package connection, we can assume it’s more tunable than the QPI implementation used to connect Bloomfield and X58 Express, since it doesn’t have to go external.

The second die is, as mentioned, manufactured at 45nm and includes the three critical components mentioned above—basically, everything you would have found in a traditional northbridge.

Intel’s memory controller is a dual-channel design supporting DDR3 memory at speeds of up to 1,333 MT/s, totaling up to 21 GB/s with DDR3-1333 installed. Depending on the motherboard, maximum capacity will differ. However, the processors themselves support up to 16GB.

Clarkdale...Clarkdale......vs. Lynnfield...vs. Lynnfield

The Clarkdale CPUs also include 16 lanes of PCI Express 2.0 on-package, just like Lynnfield (of course, Lynnfield’s are actually on the CPU die, rather than on a neighboring die). Now, if you use a Clarkdale chip on an H55- or H57-based motherboard, you’ll be limited to a single 16-lane link for graphics. If, however, you use a Lynnfield processor (a Core i5-750, for example) on an H55- or H57-based motherboard, you’ll at least have access to a pair of x8 PCI Express 2.0 slots. This is interesting because Intel’s datasheets claim Clarkdale processors at least have the ability to divide on-package PCI Express into a pair of x8 slots when used on a P55-based board. If that’s the case, then the H55/H57/Clarkdale combination is artificially prevented from supporting CrossFire or SLI, suggesting gaming enthusiasts should stick with their P55 platforms wherever possible.

According to Intel, H55/H57 aren't being aimed at the enthusiasts, so it makes sense to validate with a single x16 PCIe slot. For anyone looking to use a dual PCIe x8 arrangement, the company officially recommends going with P55 using either Clarkdale- or Lynnfield-based processors.

Finally, there’s the graphics core to discuss—we’ll get into that in more depth shortly.

Telling Them Apart

What makes the new Core i5s different from the Core i3s and the lone Pentium?

Intel's Clarkdale Lineup: In Detail
Model
CPU Clock
Max Turbo
Cores/Threads
HT/Turbo
L3 CacheGPU ClockDDR3
Core i5-670
3.46 GHz
3.73 GHz
2/4
Yes/Yes
4MB
733 MHz
1,333 MT/s
Core i5-661
3.33 GHz
3.6 GHz
2/4
Yes/Yes
4MB
900 MHz
1,333 MT/s
Core i5-660
3.33 GHz
3.6 GHz
2/4
Yes/Yes
4MB
733 MHz
1,333 MT/s
Core i5-650
3.2 GHz
3.46 GHz
2/4
Yes/Yes
4MB
733 MHz
1,333 MT/s
Core i3-540
3.06 GHz
-
2/4
Yes/No
4MB
733 MHz
1,333 MT/s
Core i3-530
2.93 GHz
-
2/4
Yes/No
4MB
733 MHz
1,333 MT/s
Pentium G6950
2.8 GHz
-
2/2
No/No
3MB
533 MHz
1,333 MT/s


Core i5 features Hyper-Threading and Turbo Boost technology (just remember that Lynnfield-based Core i5s do not include Hyper-Threading). One model employs a 900 MHz graphics core, and the other models run with a 733 MHz GPU. You can tell these chips apart from the Lynnfield-based models by their model designators: Lynnfield populates the i5-700 series, while Clarkdale exists in the i5-600 series.

Core i3 maintains Hyper-Threading, giving you the quad-threaded dual-core CPU, but sheds Turbo Boost, locking you in to one frequency. Both models employ a 733 MHz graphics core. Fortunately, there aren’t any other architectures overlapping Core i3; they’re all Clarkdales.

Clarkdale-based Pentiums lose Hyper-Threading and Turbo Boost. The graphics engine slows down to 533 MHz. But at this point, you’re talking about a sub-$90 part. Because there exists a long list of Pentium processors centering on different cores, right now it’s best to remember the G6950 model name, as it’s the only Clarkdale-based model and the only Pentium to drop into LGA 1156 platforms.

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Top Comments
  • 14 Hide
    gkay09 , January 4, 2010 3:27 AM
    ^ Many more reasons to buy AMD Phenoms II X4 in the mid-range segment...
    Only drawback with the AMD CPUs is the power consumption, that I feel can be brought down with slight undervolting...
  • 11 Hide
    dtemple , January 4, 2010 3:27 AM
    I'm looking to upgrade from my Athlon X2 @ 2.7GHz because I do more with the computer now than I did before - sometimes I'll play a game while my TV tuner is recording from my cable signal, and having more cores would help these multiple tasks run more smoothly.
    I was waiting until the Clarkdale-based i5 launched, thinking it would be a quad-core that was more competitively priced against the Phenom II X4, but it looks like a Phenom II X4 is my only option to get more cores for less money.
    The only good news coming out of this launch is that LGA1156 is not changing for the Clarkdale chips, so it looks to be the most future-proof platform to upgrade to, if one was so inclined. I'm personally going with a Phenom II since I can get one without changing motherboards. This is one of the more disappointing launches in the last year or so.
  • 10 Hide
    Zoonie , January 4, 2010 3:15 AM
    Well... I think that takes care of the dreaded "But can it play Crysis?" question regarding its GMA :D  :p  :p 
Other Comments
  • 10 Hide
    Zoonie , January 4, 2010 3:15 AM
    Well... I think that takes care of the dreaded "But can it play Crysis?" question regarding its GMA :D  :p  :p 
  • -1 Hide
    xc0mmiex , January 4, 2010 3:20 AM
    Video on page 1 not working ... "This is a private video..."
  • 0 Hide
    eklipz330 , January 4, 2010 3:20 AM
    can i ask why you teased us at the end with the 4.5ghz OC but didn't include them in the benchmarks? =[ i'm guessing most of use at tom's like to OC... it could be the difference that gets us to buy the i5 661 over the phenom II
  • 1 Hide
    cangelini , January 4, 2010 3:21 AM
    xc0mmiexVideo on page 1 not working ... "This is a private video..."


    Fixed! Had to keep it private pre-launch :) 
  • -1 Hide
    Anonymous , January 4, 2010 3:26 AM
    I really like the improvements Larrabee brought about....not! I do like the fact they are making progress but they really need to skip ahead a few generations or buy out some other company to design a GPU for themselves.
  • 14 Hide
    gkay09 , January 4, 2010 3:27 AM
    ^ Many more reasons to buy AMD Phenoms II X4 in the mid-range segment...
    Only drawback with the AMD CPUs is the power consumption, that I feel can be brought down with slight undervolting...
  • 11 Hide
    dtemple , January 4, 2010 3:27 AM
    I'm looking to upgrade from my Athlon X2 @ 2.7GHz because I do more with the computer now than I did before - sometimes I'll play a game while my TV tuner is recording from my cable signal, and having more cores would help these multiple tasks run more smoothly.
    I was waiting until the Clarkdale-based i5 launched, thinking it would be a quad-core that was more competitively priced against the Phenom II X4, but it looks like a Phenom II X4 is my only option to get more cores for less money.
    The only good news coming out of this launch is that LGA1156 is not changing for the Clarkdale chips, so it looks to be the most future-proof platform to upgrade to, if one was so inclined. I'm personally going with a Phenom II since I can get one without changing motherboards. This is one of the more disappointing launches in the last year or so.
  • 4 Hide
    cangelini , January 4, 2010 3:27 AM
    eklipz330can i ask why you teased us at the end with the 4.5ghz OC but didn't include them in the benchmarks? =[ i'm guessing most of use at tom's like to OC... it could be the difference that gets us to buy the i5 661 over the phenom II


    We have another overclocking piece planned--I wanted to get a Core i3, at least, to include :) 
  • 3 Hide
    Anonymous , January 4, 2010 3:30 AM
    I would love to see what GTA IV would do do the dual cores in gaming! I do know that its a bear of a game on the CPU and it would truly show off if hyperthreading could actually make a major difference.
  • 0 Hide
    maximus20895 , January 4, 2010 4:26 AM
    Great video once again! Thanks for this and the review itself. Very informative. I really liked the graph on the first page too :) 
  • 0 Hide
    WINTERLORD , January 4, 2010 5:03 AM
    good touch on the world of warcraft fraps. although not very playable on high settings is good to know what speeds it actualy gets
  • 2 Hide
    noob2222 , January 4, 2010 5:11 AM
    Would be nice to know if this thing can handle blue ray playback, as some of these would probably be sold as a HTPC. Ya, they put features for it, but does it play or not?

    Last preview I read showed it doing fine in windowed mode, but blowing chunks at full screen playback, dropping to 15fps and lower.
  • 3 Hide
    dupaman , January 4, 2010 5:25 AM
    Idle power in the 70s for an IGP-based system is a huge failure not a win, though using an 1100W PSU probably deserves a lot of the blame. Systems built on the 780G, 730i, G4x, etc. (similar to this test platform, but use a more appropriate PSU) idle in the 40s.
  • 1 Hide
    shubham1401 , January 4, 2010 6:22 AM
    Nice dual....
    E8500 was beaten badly...

    Wud really like to see what these chips can do once overclocked.
  • 6 Hide
    thejerk , January 4, 2010 7:08 AM
    Where are the H55 and H57 motherboards priced? So what if the processor is $200 if the motherboard is going to be another $200 on top of it, like P55. I'm not an AMD fanboi, but for less than $300, you can get excellent computing power. Platform cost is where AMD rules, currently.
  • 0 Hide
    Stardude82 , January 4, 2010 7:17 AM
    Very meh at their price points with disappointing idle consumption. Intel is just biding time until AMD's 32 nm process is ready. No reason why they couldn't have a 4 GHz stock chip, load power proves it.

    If you use a E8600 with integrated G45 graphics, I bet you that power consumption will be lower that the 661 (integrated). This GPU-on-package is all just a marketing ploy.

    I really wish you had benchmarks for the low end chips though I doubt IT managers will be running out to replace their fleets of E7500's.
  • -6 Hide
    liquidsnake718 , January 4, 2010 7:22 AM
    same as the p55 but less room for Gpu's.... and newer h55,h57 onboard gpu.... well I guess if you really want to get over all the unneeded jargon and you dont really have a budget just skip this and go X58..... regardless.... even if you have a little extra money to spare and you ARE on a budget, save on the 2nd GPU,monitor, or RAM and get an X58 now!

  • 1 Hide
    mau1wurf1977 , January 4, 2010 8:12 AM
    I think there is a big mistake in the gaming benchmarks...

    Wolfdale is a awesome gaming chip. Its a first to me that the Core 2 Quad is faster in Crysis and all the other games vs. Wolfdale...

    Are you sure it was running at full speed?
  • -6 Hide
    mau1wurf1977 , January 4, 2010 8:12 AM
    I think there is a big mistake in the gaming benchmarks...

    Wolfdale is a awesome gaming chip. Its a first to me that the Core 2 Quad is faster in Crysis and all the other games vs. Wolfdale...

    Are you sure it was running at full speed?
  • -6 Hide
    mau1wurf1977 , January 4, 2010 8:20 AM
    That Yorkfield is 2.66 GHz! No chance in hell it beats the E8500 in gaming...

    I hope this is just a mistake...

    E.g. in Crysis 1920 x 1200 with (breace yourself) 8x AA! No way in hell are these scores correct.

    Did you test the E8500 with a slower video card?
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