1 00:00:00,000 --> 00:00:05,600 So many of us only ever end up using one slot on our motherboard, usually for a GPU. 2 00:00:05,600 --> 00:00:09,200 But what would happen if you filled all of them? 3 00:00:09,200 --> 00:00:12,560 It's not that unrealistic. Let's say you're a gamer. 4 00:00:12,560 --> 00:00:16,560 You gotta have your GPU, but you also need to connect your desktop to Wi-Fi, 5 00:00:16,560 --> 00:00:22,880 so you throw in a wireless card. You stream, so you need to capture card, and you've got a pretty big game library, 6 00:00:22,880 --> 00:00:27,360 so you're out of M.2 slots, so you add some more storage with one of these babies. 7 00:00:27,920 --> 00:00:31,600 Then there's the fact that you've got this unnatural attraction to PCs with 8 00:00:31,600 --> 00:00:36,320 lots of USB ports, so you throw in one of these, and that's five cards, 9 00:00:36,320 --> 00:00:41,200 which happens to be the same or more than most modern motherboards can accept. 10 00:00:41,200 --> 00:00:43,600 Will this overload your system in some way? 11 00:00:44,400 --> 00:00:48,400 Well, as is the case with so many things in PC land, 12 00:00:48,400 --> 00:00:52,240 the answer depends on what kind of CPU and motherboard you have, 13 00:00:52,240 --> 00:00:55,840 what cards you're using, and exactly what it is you're trying to do. 14 00:00:56,480 --> 00:01:01,920 Further complicating matters is that even PCI Express slots that look identical 15 00:01:01,920 --> 00:01:04,000 can operate at very different speeds. 16 00:01:04,960 --> 00:01:09,680 Let's break it down. Some slots connect directly to your CPU, 17 00:01:09,680 --> 00:01:12,960 while others connect to your motherboard's chipset. 18 00:01:12,960 --> 00:01:17,600 The CPU direct ones are generally going to provide the smoothest experience, 19 00:01:17,600 --> 00:01:20,560 since they're not going to be shared with any other devices. 20 00:01:21,280 --> 00:01:26,720 The issue is that the PCIe lanes, the data paths that feed these slots, 21 00:01:26,720 --> 00:01:30,080 add a lot of cost and complexity to the CPU. 22 00:01:30,800 --> 00:01:38,080 That's where chipset lanes come in. In PC terms, the chipset is a chip, or well, set of them, if you will, 23 00:01:38,080 --> 00:01:42,320 that lives on your motherboard and handles a great deal of your computer's input and 24 00:01:42,320 --> 00:01:49,280 output, or IO. SATA ports, USB ports, and network ports are commonly connected to the chipset, 25 00:01:49,280 --> 00:01:54,080 and on modern platforms, that requires a lot of PCIe lanes. 26 00:01:54,640 --> 00:02:00,960 Intel's Z790 chipset, for example, supports up to 28 additional PCIe lanes. 27 00:02:01,600 --> 00:02:08,720 But this presents a problem. The problem is that the chipset itself has to have some kind of link to your CPU, 28 00:02:08,720 --> 00:02:13,600 and this link usually takes the form of, you guessed it, PCIe lanes. 29 00:02:14,160 --> 00:02:17,920 Now, as you can imagine, there wouldn't be much cost savings if this link 30 00:02:17,920 --> 00:02:21,360 had the same number of lanes as the downstream chipset, 31 00:02:21,360 --> 00:02:27,920 so typical desktop systems cut that link all the way down to just eight or even four lanes. 32 00:02:28,640 --> 00:02:32,640 Now, in most cases, that's not a huge deal, and to illustrate why, 33 00:02:32,640 --> 00:02:39,920 let's think of our system kind of like a restaurant. The CPU can be the kitchen, and the connected devices can be our customers. 34 00:02:40,480 --> 00:02:45,120 Our GPU is going to sit at the 16-seater VIP table over here. 35 00:02:45,120 --> 00:02:48,720 Every guest gets a dedicated chef, so no one ever goes hungry, 36 00:02:48,720 --> 00:02:53,440 and the same goes for the four-seater family and friends table where our boot SSD hangs out. 37 00:02:54,080 --> 00:02:58,640 As for the rest of the dining room, well, hey, as long as their orders are staggered, 38 00:02:58,640 --> 00:03:04,480 nobody ends up waiting too long for their meal, and in the real world, that's usually how things go down. 39 00:03:04,480 --> 00:03:08,720 Expansion cards like Wi-Fi, Sound, or USB and SATA cards, 40 00:03:08,720 --> 00:03:14,800 even capture cards, are very unlikely to all be operating at peak capacity at the same time. 41 00:03:15,120 --> 00:03:20,240 And even if they did, they wouldn't come close to saturating that link back to your CPU 42 00:03:20,240 --> 00:03:22,240 because of their relatively low data rates. 43 00:03:23,280 --> 00:03:29,120 However, where you can run into problems is if you're using your chipset lanes for high-speed 44 00:03:29,120 --> 00:03:34,720 storage. Let's say, for example, you work with large amounts of high-resolution video footage. 45 00:03:34,720 --> 00:03:39,280 You could overwhelm the link between the chipset and the CPU in multiple ways. 46 00:03:39,280 --> 00:03:44,720 For example, by transferring footage from an external drive that uses the fastest versions of 47 00:03:44,800 --> 00:03:51,040 USB or Thunderbolt to a high-speed PCIe drive that's also running off the chipset. 48 00:03:51,040 --> 00:03:55,120 This could result in lower than expected speeds and even slow down 49 00:03:55,120 --> 00:04:02,800 anything else that is connected to the chipset. Imagine, for instance, a capture card that starts dropping frames whenever you do a file transfer. 50 00:04:03,600 --> 00:04:13,440 Another thing to watch out for, especially you gamers, is that many CPUs allow the 16-lane GPU slot to be split into two 8-lane slots. 51 00:04:14,080 --> 00:04:17,600 This is good because it gives users the flexibility to install 52 00:04:17,600 --> 00:04:22,400 two GPUs for machine learning or a GPU and another high-performance accelerator. 53 00:04:23,040 --> 00:04:27,840 But it comes at the cost of reducing the bandwidth to your main GPU. 54 00:04:28,480 --> 00:04:33,200 Making matters worse, the way the lanes are split up is not always easy to control. 55 00:04:33,760 --> 00:04:37,120 You might consult your motherboard manual, good idea by the way, 56 00:04:37,200 --> 00:04:41,760 and think, oh, okay, these two slots can share 16 lanes, 57 00:04:41,760 --> 00:04:45,120 but I only really need one lane for this Wi-Fi card. 58 00:04:45,120 --> 00:04:47,520 That leaves 15 lanes for my GPU. 59 00:04:48,320 --> 00:04:52,560 But it doesn't work like that. The mere act of installing another card, 60 00:04:52,560 --> 00:04:57,440 any card in that slot will more than likely cut your GPU bandwidth in half. 61 00:04:58,320 --> 00:05:01,600 Fortunately, your gaming performance won't drop that much, 62 00:05:01,600 --> 00:05:05,840 but there are cases where these fine details can make a big difference. 63 00:05:06,560 --> 00:05:12,560 This high-speed network card, for example, uses 16 lanes that run at Gen 4 speeds. 64 00:05:12,560 --> 00:05:16,960 If we put it into a Gen 3 motherboard, that's okay, it'll work, 65 00:05:16,960 --> 00:05:24,400 but it will run at half the bandwidth. But then, if the slot on that motherboard were to only get 8 lanes, 66 00:05:24,400 --> 00:05:30,240 now we've cut the overall bandwidth in half again to just one quarter of what the card expected. 67 00:05:32,640 --> 00:05:36,240 Don't get too freaked out, though. You don't have a network card like that at home, 68 00:05:36,240 --> 00:05:39,440 and unless you're moving around large amounts of data regularly, 69 00:05:39,440 --> 00:05:43,040 you likely won't notice slowdowns just from having all of your slots filled. 70 00:05:43,600 --> 00:05:47,520 If you do need more lanes though, the good news is there are solutions. 71 00:05:47,520 --> 00:05:51,760 Workstation and enterprise platforms like AMD's Threadripper and Epic 72 00:05:51,760 --> 00:05:57,600 or Intel Xeon are built with a huge number of PCIe lanes connected directly to the CPU. 73 00:05:58,240 --> 00:06:04,240 The only problem is that if you need one of those, you're gonna have to figure out how to get one of your kidneys out as painlessly as possible. 74 00:06:05,440 --> 00:06:13,040 Thanks for watching! If you guys liked this video, check out our other video on PCI Express Gen 7.