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

Benchmark Results: 3DMark Vantage

Early on, we see some genius to the way Intel has implemented PCI Express on Core i5—at least for gamers using a single card.

If you compare i5 to i7 using one Radeon HD 4870 X2, scores are consistently higher at each of our three test settings. Core i5 is even able to beat the 2.83 GHz Core 2 Quad, which, clock for clock should be faster in many gaming situations (and sure enough, in two of the three 3DMark runs, Core 2 Quad is faster than Core i7, but loses all three to Core i5). Phenom II edges closer as the details increase, but only really bests Core i7 in the overall metric.

Add a second card, though, and the situation changes a bit. Suddenly, Core i7 jumps into the lead, bolstered by its two PCI Express x16 links. Core i5 extends its lead over Core 2 Quad—presumably since its Radeon HD 4870 X2s are leveraging on-die PCIe connectivity, while the P45’s twin eight-lane links are forced to communicate over a 1,333 MHz front side bus.

At 2.8 GHz, the Core 2 Quad and Phenom II trade blows. Nothing notable though, since they both lose out to Core i5.

A more telling gauge of graphics performance, the GPU score represents a weighted arithmetic mean of the raw scores taken from each of the two graphics tests in Vantage. As you can see, with a single card installed in each platform (thus, all contenders getting 16 lanes of PCIe 2.0), the Core i5 is the fastest, clock for clock. Clearly, the on-die connectivity is working to its benefit.

Add the second card, though, and the inflexible x8/x8 design actually turns into a detriment, as the X58’s dual x16 links allow it the lead across the board. The good news for mainstream gamers who weren’t even considering X58, however, is that Core i5 is still able to best Intel’s Core 2 Quad and its P45 platform. Incidentally, in two of the three tests, AMD’s Phenom II X4 920 also slides past the Core 2 Quad (falling short of the i5).

Consisting of an AI test and a physics test, both parallelized, we see the Core i5 and Core i7 roughly on par, with the Core i7 trending just a tad higher overall. However, both CPUs beat Intel’s Core 2 Quad, which in turn bests the Phenom II X4. Of course, the results in a synthetic metric like this one are subject to myriad optimizations and only really derive meaning from parallels to real-world proof points. So let’s get into a couple of real games and see how this initial analysis pans out.

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.