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In Theory: How Does Lynnfield's On-Die PCI Express Affect Gaming?

Benchmark Results: Stalker: Clear Sky

Our first game test hammers graphics performance. With one graphics card installed, the Core i5 is unable to translate its advantage in 3DMark Vantage into a win over Core i7. The pricier platform edges out the newcomer—its two advantages are Hyper-Threading and three channels (rather than two) of DDR3 memory.

Core i5 does best the slightly higher-clocked Core 2 Quad by a fairly substantial margin, though, with a lead that shrinks as resolution increases. It puts an even bigger gap between itself and the 2.8 GHz Phenom II.

Dropping a second card into our test platforms does very little for performance at 1680x1050 or 19200x1200—a result of our relatively slow CPU clocks holding back performance. Let’s look at the red bars instead, representing 2560x1600. First up, Core i5 versus Core i7. The even result between these two platforms with one graphics card installed suggests that one 4870 X2 isn't enough to flesh out differences between the two. With a pair of cards, the i7 takes a quantifiable lead. Clearly, dividing PCI Express up into x8 slots is hurting i5. Is the difference palpable in the real-world? Almost certainly in this case, it is not.

Once again, i5 puts in a couple of frames above and beyond Core 2 Quad and a few more on top of AMD’s Phenom II—both platforms clearly limited by their host processors at lower resolutions (thus, you see CrossFire adding zero performance).

Anti-aliasing adds a significant graphics workload, partially mitigating the CPU bottleneck experienced previously.

With one card installed, i5 and i7 achieve almost exact parity. And for that matter, Core 2 Quad and Phenom II are remarkably close as well, suggesting a single Radeon HD 4870 X2 is now the component holding us back.

Add the second card and the range opens up a bit. Core i5 once again trails i7 when its PCI Express lanes get divided up between two powerful video cards. The same happens to Core 2 Quad and Phenom II, though, so it’s not really a surprise to see i5 besting both platforms at 2.8 GHz.

Chris Angelini is an Editor Emeritus at Tom's Hardware US. He edits hardware reviews and covers high-profile CPU and GPU launches.
  • megabuster
    AMD better have something up its sleeves or it's instakill.
  • rambo117
    AMD... your loosing your game...
  • dirtmountain
    A PhenomII x4 920? ouch
  • bucifer
    I do not agree with the choices made in this article. You don't buy 2*4870x2 and the you slam a x4 920. The choices do not make sense.

    You should have used the best cpu(ex i7 920 oc@4GHz) to try to eliminate all bottlenecks and truly emphasize the limitations of x8/x16 pci-e lanes.

    The rest of the testing was done to include the new i5 which is not bad but not relevant for the bottleneck. I know many people would like to see how i5+p55 handles the gpu power but it's a highly unlikely scenario that someone would actually but such powerful and expensive cards on pair them with a cheaper cpu and a limited platform.

    I just think you should have tested things separately in different articles.
  • radnor
    I know you used a 2.8Ghz Deneb for Clock-per-clock comparisons. MAkes sense. But a 2.8 Ghz Deneb is something really no unlocked. Ussually unlock versions go 3.5Ghz on stock VID, non BE PArts can reach 3.3Ghz safely.

    A 2.8 Deneb/Lynnfield/Bloomfield have completely diferent prices. You are comparing a R6 vs a R1. I7 is the Busa trouting everybody else. Of course the prices are very diferent.
  • cangelini
    Gents, if you want to see the non-academic comparisons, I have the 965 BE compared in two other pieces for more real-world comparisons!,2410.html
    Thanks for the feedback notes!
  • bounty
    "Will Core i5 handicap you right out of the gate with multi-card configurations? The aforementioned gains evaporated in real-world games, where Core i7’s trended slightly higher, perhaps as a result of Hyper-Threading or its additional memory channel"

    Well you answered will i5 handicap you without hyperthreading, x8 by x8 and dual channel. It will by 5-10% If you wanted to narrow it down to memory channels, hyperthreading or the x8 by x8 you could have pice the game with the biggest spread and enabled each of those options selectively. Would have been kinda interesting to see which had the biggest impact.
  • Shnur
    Great article! But then again... I don't see why a 955 wasn't used in this scenario... since the 920 is thing that nobody uses. Already that we know that i7 is superior to AMD flagship in multi-GPU configurations you're taking a crappy AMD CPU, buying a 790GX doesn't mean you're going to cut on the chip... and you're talking about who's performing better in 8x lanes... from my point of view it's a bad comparison, and there should have been a chip that'll be actually able to take a difference between 1 card and two and the from 16x and 8x.
    And thanks for the other linked reviews, but I'm not talking about comparing the chips themselves, I'm trying to figure out is 8x still good enough or I need to pay more for 16x?
  • cangelini
    Thanks much for the feedback--again, this wasn't meant to be about the CPUs, but the PCI Express links. If you want to know about the processors themselves at retail clocks, check out the gaming story, which does reflect x16/x16 and x8/x8 in the LGA 1366 and LGA 1156 configs.
    Hope that helps!
  • Shadow703793
    megabusterAMD better have something up its sleeves or it's! do you mean instagib?

    Joking aside, AMD needs something to counter this.