Intel’s Second-Gen Core CPUs: The Sandy Bridge Review

Overclocking: Sandy Bridge Changes The Game

As you probably already know, Sandy Bridge dramatically alters the way enthusiasts can approach overclocking. For a great many, the days of wringing massive gains out of a scalable architecture like Nehalem are over. Options do still exist, though.

The back-story is already pretty well known. In an effort to simplify its design (which really does make sense from an engineering perspective), Intel integrated the clock generator into the 6-series chipsets. Now, one clock affects the entire system, meaning you can’t independently set the frequencies of various subsystems like PCI Express and the DMI.

Unfortunately, PCI Express doesn’t like to operate very far outside of its specification, so any significant deviation beyond the new 100 MHz BCLK causes problems. Though there’s generally a few percentage points worth of wiggle room, the days of taking Nehalem’s 133 MHz BCLK up to 200+ MHz are history. Overclockers are basically losing one of the two variables that previously affected processor performance. Intel addresses this in two ways.

First, it carries over the unlocked K-series that first surfaced back in May of last year. These parts top out at a 57x ratio multiplier, enabling frequencies of up to 5.7 GHz without touching the BCLK. Intel says the 57x is largely a “design consideration,” whatever that means. The good news for the LN2 crowd is that the company is working on a BIOS that’ll go higher and apply to today’s CPUs. The K-series chips also offer "unlocked" DDR3 memory ratios, which aren't literally unlocked, but rather exposed up to DDR3-2133 (higher than most kits are capable of going anyway). Power and current limits can also be custom-specified, too.

There are only two K-series parts at launch: the Core i7-2600K and the Core i5-2500K. The unlocked i7 costs $23 more than the partially-unlocked version of the same chip, while the i5 runs $11 more expensive than its less-flexible equivalent. When you consider that, at its default settings, the Core i5-2500K runs at 3.3 GHz and Turbo Boosts up to 3.7 GHz, compared to the Core i5-760 at 2.8 GHz, an unlocked Sandy Bridge chip for $11 extra is actually pretty damn sexy.

If you don’t buy a K-series chip and instead grab a Core i7-2600, Core i5-2500, -2400, or -2300 (along with a P67-based motherboard), you’ll still have access to “limited unlocking.” This basically means you can set clock rates up to four speed bins above the highest Turbo Boost frequency setting available at any given level of processor activity.

So, take a Core i7-2600 as an example. The chip’s base clock is 3.3 GHz. With four cores active, it gets one bin worth of additional performance—3.4 GHz. Four bins above that would be 3.8 GHz. With two cores active, Turbo Boost bumps it up two bins, to 3.5 GHz. Limited overclocking makes 3.9 GHz available in that case. In a best-case scenario, only one core is active. Turbo Boost adds four bins of frequency, yielding 3.7 GHz, and Intel’s overclocking scheme lets you run at up to 4.1 GHz.

Anyone with a K-series CPU overclocking on air is going to be in good shape. Thomas and I both have Core i7-2600Ks that’ll do 4.7 GHz at 1.35 V all day long. More mainstream folks with non-K i5s and i7s will at least have an extra 400 MHz to milk from their chips. It’s the value-oriented buyers with processor budgets between $100 and $150 (where AMD offers some of its best deals) who get screwed. The only two Sandy Bridge-based options under $175 are the Core i3-2100 and -2120 at 3.1 and 3.3 GHz, respectively. No Turbo, no BCLK option, no limited unlock—those chips are quite literally stuck.

As with the integrated graphics situation, I think that Intel missed the boat by trying to use overclocking as a differentiating feature. The guys who hit 7 GHz+ in our recent K-series overclocking contest are getting artificially capped. The folks buying at the bottom end of the mainstream stack can’t touch their BCLK or multiplier settings. And unless you buy one of two K-series SKUs, you’re on a Turbo Boost + 400 MHz leash.

Hopefully AMD is taking notes. Though most of its newest 45 nm processors don’t offer a ton of headroom, sticking 32 nm manufacturing later this year could make flexible Bulldozer-based CPUs very attractive to anyone who feels like Intel is muscling them out of overclocking at the high- and low-end.

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  • JE_D
    BENCHIES! Thanks Tomshardware!
  • Editor, page 10 has mistakes. Its LGA1155, not LGA1555.
  • cangelini
    MoneyFace pEditor, page 10 has mistakes. Its LGA1155, not LGA1555.

    Fixed, thanks Money!
  • juncture
    "an unlocked Sandy Bridge chip for $11 extra is actually pretty damn sexy."

    i think the author's saying he's a sexually active cyberphile
  • cangelini
    juncturei think the author's saying he's sexually active

    Just this.
  • fakie
    Contest is limited to residents of the USA (excluding Rhode Island) 18 years of age and older.

    Everytime there's a new contest, I see this line. =(
  • englandr753
    Great article guys. Glad to see you got your hands on those beauties. I look forward to you doing the same type of review with bulldozer. =D
  • joytech22
    Wow Intel owns when it came to converting video, beating out much faster dedicated solutions, which was strange but still awesome.

    I don't know how AMD's going to fare but i hope their new architecture will at least compete with these CPU's, because for a few years now AMD has been at least a generation worth of speed behind Intel.

    Also Intel's IGP's are finally gaining some ground in the games department.
  • cangelini
    fakieContest is limited to residents of the USA (excluding Rhode Island) 18 years of age and older.Everytime there's a new contest, I see this line. =(

    I really wish this weren't the case fakie--and I'm very sorry it is. We're unfortunately subject to the will of the finance folks and the government, who make it hard to give things away without significant tax ramifications. I know that's of little consolation, but that's the reason :(

  • LuckyDucky7
    "It’s the value-oriented buyers with processor budgets between $100 and $150 (where AMD offers some of its best deals) who get screwed."

    I believe that says it all. Sorry, Intel, your new architecture may be excellent, but unless the i3-2100 series outperforms anything AMD can offer at the same price range WHILE OVERCLOCKED, you will see none of my desktop dollars.

    That is all.
  • DjEaZy
    ... will wait til 'buldozer'... and two things may happen... the buldozer at the price point will kick ass... or the sandy bridge parts will get cheaper...
  • touchdowntexas13
    There is some pretty cool stuff going on here. I like the way the article points out the good and the bad. As for me I really am mystified at Intel's decision to only put the higher end graphics in the k-models as most likely anyone buying them will be going for the P67 platform that doesn't even use the integrated graphics. It would have been soooo much better for the HTPC crowd if there were some lower end chips with the better integrated graphics. I guess somehow this is money motivated???

    As for overclocking, well it seems a bit odd in the way it is being implemented. But for $216, I can't complain too much about a quad-core with a base clock of 3.3 GHz. Some enthusiasts won't like the limited overclocking features, but others will welcome the simplified approach.

    I will be building my brother a new gaming computer for graduation this summer and now I have another viable option to look at. I had planned on going with a P55 + i5 760, but now I will need to consider the P67 + i5 2500K.

    Waiting on bulldozer...
  • jyar727
    I mean this looks like a thorough test but its really not. I wanted to see an I7 1:1 clock performance comparisons. Mainly, 3.4GHz I7-950 vs 3.4GHz I7-2600K. Obviously 3.4 GHz new tech would usually beat a 3.0 current tech in benches. UGH. lame lame lame. Really want to see this comparison instead.
  • silversurfernhs
    Shouldn't the title be second gen Core i series... because Core 2s were second gen Cores, weren't they?
  • Tamz_msc
    Where is the 980x in these benchmarks?
    Other than that its a great article, and I'm drooling over QuickSync!
  • Maziar
    Thanks for the review Chris :)
    QuickSync definitely looks interesting.
  • Ramar
    I just bought an i5-760 system on 12/30 from newegg, I guess I wasn't paying attention to when Sandy Bridge would actually be released. It's not here yet, so I could just send the mobo and cpu back when they get here, but I don't see enough justification as a gamer to move to the 2500k. Based on the number of 1.35V 4.7ghz for the 2600k, I would assume that on stock voltage it doesn't get much higher in frequency than my 760 will, and I don't like raising stock voltage.

    This is all very nice, but I'll keep my bclk control for now and maybe move up when I get out of college in seven months and the tech is set in stone and dropping in price a little.

    Not a bad chip, and I'm excited to see where they go with it. =]
  • Hellbound
    Is sandy bridge the replacement to the x58 chipset? I thought I read somewhere they were planning on x68 sometime in 2011.
  • djdarko321
    Remember though as this is the lower end Sandy Bridge platform NOT THE MAIN LGA2011 socket. As Intel decided to release for the mainstream first before the enthusiasts this go around.
  • Tamz_msc
    Just looked at the AnandTech review and here is their opinion -

    In all but the heaviest threaded applications, Sandy Bridge is the fastest chip on the block—and you get the performance at a fairly reasonable price. The Core i7-2600K is tempting at $317 but the Core i5-2500K is absolutely a steal at $216. You're getting nearly $999 worth of performance at roughly a quarter of the cost.

    These things are as fast as the i7 980X and in some cases they're even faster!
  • swiftor
    i5-2500k + p67 ftw!
  • nekromobo
    What if you throw something like 8k x 4k or 4k X 4k resolution video to QuickSand.. Sync :)

    Nice review, but personally still not going to replace my 3.6ghz C2Quad.. when will this cpu die so I can replace it!
  • Shuge1
    Im just waiting for bulldozer to get me out of buyin the i5 2500k
  • Reynod
    Quick Synch is just downright embarrasing for AMD ...