 So the other day I was shopping for a state-of-the-art CPU for my gaming and productivity PC, when I realized that Intel's latest 5820K and 5930K both have six processing cores with hyperthreading, both have 15 megs of cache, they have a clock speed difference of only 6%, and yet the difference in retail price is around $200. Whaa? Ohhhhh, there's the gotcha. The 5820K only has 28 PCI Express Gen 3 lanes, you know, the electrical connections behind the slots that we use for graphics cards and other expansion cards, compared to 40 on the 5930K. What a strange way for Intel to differentiate its mid-tier 2011 3 CPU from its entry level one. Corsair Gaming RGB keyboards feature precision Cherry MX RGB keyswitches for 16.8 million color per key backlighting for virtually unlimited customization. Click now to learn more. Let's start with a brief explanation of what PCI Express or PCIe lanes are, and what they're good for. Unlike previous expansion slots like AGP and PCI, PCIe is a very simple, but very powerful, and very powerful keyboard. And what they're good for, unlike previous expansion slots like AGP and PCI, PCI Express has a physical size and an electrical operating mode that can be independent from each other. Power is provided by the pins near the key in the connector, and the rest of the connector is used or not used to provide more or less bandwidth to the device that is plugged into it. The more bandwidth, the more lanes are said to be being used for communication. The most common speeds are 1x, 4x, 8x, and 16x. So here's a cool fact. The different bus width cards and slots are actually interoperable. That means that installing a 1x card in a 16x slot is fine, and you can even go the other way around. In this video, I cut out the back of a smaller slot and put a larger card into it. All that happens is that both the slot and the card will now operate at the speed of the lowest link in the chain. So that's what's going to happen if we plug our PCIe 16x graphics card into what appears to be a 16x slot, but if the CPU in our system doesn't have enough PCI Express lanes to provide the full 16 lanes. Your motherboard manual will give you more specifics with a slot-by-slot breakdown of how it's going to work, but basically it'll simply interface with your PC at a lower speed, usually 8x. Well that sounds horrible, Linus. Won't cutting the link speed to my graphics card in half tank its performance? Not necessarily. We're on the third generation of PCI Express, with each new generation doubling the theoretical speed of the previous one. That means a modern Gen 3 PCIe 16x slot can communicate four times faster than an original Gen 1 16x slot, or another way of thinking about this is that a Gen 3 4x slot is equivalent to a Gen 2 8x or a Gen 1 16x slot. But while we already know that from countless articles that exist on the topic in the past that no previous generation of 8x slot has bottlenecked a then modern high-end graphics card, with X99's positioning as the high performance platform of choice for enthusiasts and for gamers, I think it's fair to say that folks may be running not just one, but two or even more graphics cards at a time, and this is where concerns start to arise, especially given that AMD, and I suspect also Nvidia, is starting to do more inter-card communication over PCI Express when running in Crossfire, and again I suspect SLI, versus relying on those dedicated connectors on the top of the cards. So let's introduce the test. To eliminate the variable of the slightly different clock speed of the two CPUs, and since overclocking K-series chips is so easy these days, we're going to run both processors at 4 GHz, a very conservative overclock that anyone should be able to attain. For the rest of the bench we've got a Gigabyte X99 Gaming 5 4-way SLI compatible motherboard with 16 gigs of DDR4 2400 MHz memory from ADATA, thanks to both of them for providing the hardware for the test bench. We're going to be using four Nvidia GeForce GTX 980 4-gig graphics cards, and we're going to be running all this off, of course, our AX1500i power supply so that nothing melts during the benchmarking process. And here are the numbers. FRAPS was used to take average frame rates for each of our standard test runs, and all games were run at 4K on pretty demanding settings to ensure that we were pushing the hardware as hard as possible. As expected, a single graphics card config is not affected in any way since it's running in 16x mode on either CPU. But dual cards will be running at 8x 8x on a 5820K and 16x 16x on an effective doubling on a 5930K, so I guess as much as it might be a little bit more counterintuitive, they both ran the same, so there you go. In 3-way SLI, both CPUs have to give up at least one 16x slot, but again, the results are not really affected in any way beyond sort of your standard variants from one run to another. And then finally, in 4-way SLI, we see... oh, actually, there's a difference here. As you may or may not have noticed, our 28-lane CPU doesn't have any numbers for 4-way SLI. Nvidia requires graphics cards to be plugged into an 8x slot at least for SLI certification, so only 40-lane CPUs have support for this configuration. However, it should be noted that even at 4K, the benefit of a fourth card is fairly small, and 3-way remains our recommended max config even if you feel the need to spend over $1,000 on a bunch of graphics cards to put in your system. It should be noted that AMD does not have the same limitation for Crossfire, so you could run four graphics cards if you really wanted to in that case, but our recommendation remains the same anyhow. So that's the story, or at least most of it for gamers anyway. Compared to the mainstream Z97 platform, where it should be noted that even the highest-end CPUs have a mere 16 lanes, Intel's enthusiast X99 platform in general and the Core i7-5820K CPU in particular is a great choice even for multi-graphics card gamers if they want to reap the benefits of an extra two processing cores, DDR4 memory, and higher overall memory capacity limits. Things do get a little bit dicey for non-gamers though when it comes to other PCI expansions, so make sure that you consult the manual of the motherboard you want before investing in this particular CPU, because you may find that the M.2 high-speed storage slots, and in some cases even built-on ports like SATA Express and USB 3 headers might not work with too many PCI Express cards plugged in or even be available at all with a 28-lane CPU. So if in doubt, head over to the CPUs and Motherboards section of the LinusTechTips.com forum where our helpful community will get you sorted out. Thanks for watching guys, I hope this video put to rest some of the concerns about oh no, the affordable one doesn't have enough PCI Express lanes. I hope you all feel a little bit better. Like the video if you liked it, dislike it if you disliked it, leave a comment letting me know, did you learn something today? Is this something you already knew? Was it nice to have it validated anyway? Also check out the link in the video description, you can support us by buying a cool t-shirt like this one, giving us a monthly contribution, or that other thing. Right, changing your Amazon bookmark to one with our affiliate code so that we get a small kickback whenever you buy CPUs or graphics cards or whatever else. Thanks again for watching and as always, don't forget to subscribe.