1 00:00:00,240 --> 00:00:08,559 So, as a follow-up to my recent video where I took two GTX 580s, threw them on 2 00:00:05,920 --> 00:00:15,200 the Gigabyte G1 Gorilla motherboard, and I tested in dual 16x mode in SLI and 3 00:00:12,080 --> 00:00:17,920 dual 8x bandwidth mode in SLI. I am 4 00:00:15,200 --> 00:00:23,119 going to be taking an even higher an even more demanding card, the Radeon 5 00:00:21,000 --> 00:00:30,080 HD6990, and I'm going to be running it in a single card configuration in a 16x 6 00:00:25,840 --> 00:00:32,640 slot, an 8X slot, and finally a 4X slot 7 00:00:30,080 --> 00:00:37,360 to find out what difference there is. In terms of performance, I'll be using the 8 00:00:34,000 --> 00:00:39,760 3D Mark 11 extreme preset. Now, please 9 00:00:37,360 --> 00:00:45,920 note that the extreme preset will not show as much of a difference as one of 10 00:00:42,399 --> 00:00:48,879 the lower quality presets, uh, such as 11 00:00:45,920 --> 00:00:53,600 the entry or performance presets. But what it does give us is a more realistic 12 00:00:51,440 --> 00:01:01,280 real world scenario because most people are not going to be using a 6990 to run 13 00:00:57,120 --> 00:01:02,559 Quake 3 at 1024 x 768. So, you're going 14 00:01:01,280 --> 00:01:07,920 to be turning up the details, you're going to be turning up the res. So, that is the scenario that we will be looking 15 00:01:05,840 --> 00:01:13,119 at. Something to bear in mind before I get too far into my testing here is that 16 00:01:10,400 --> 00:01:18,159 the top slot at 16 and the second slot at 8X are both running off the PCI 17 00:01:15,680 --> 00:01:22,640 Express controller integrated into the Sandy Bridge CPU on this board which is 18 00:01:20,560 --> 00:01:27,600 clocked at 4.7 GHz by the way to eliminate any CPU bottlenecking or as 19 00:01:24,960 --> 00:01:33,640 much as possible. The bottom slot actually runs off of the chipset at 4x 20 00:01:31,119 --> 00:01:38,000 speed. So, it has an additional disadvantage that is not shared by the 21 00:01:36,320 --> 00:01:41,600 top two slots. So, just bear that in mind. Take the results with a bit of a 22 00:01:39,360 --> 00:01:47,360 grain of salt, but I don't have another platform handy where I can show you 16x, 23 00:01:43,759 --> 00:01:51,880 8x, and 4x where they will all be equal. 24 00:01:47,360 --> 00:01:55,040 So, my 16x result is a score of 25 00:01:51,880 --> 00:01:57,680 3,330. So, I'll be back with 8x and 4x 26 00:01:55,040 --> 00:02:02,399 results shortly. Now, this may look like a stupid configuration. I've got my 6T90 27 00:02:00,159 --> 00:02:06,320 and a GTX 580 here. But the reason I've installed the GTX 580, which won't 28 00:02:04,320 --> 00:02:12,520 affect my benchmark scores in any way, is to force these PCIe lanes to go from 29 00:02:08,959 --> 00:02:16,480 16x to 8x8x. So, you can see here within 30 00:02:12,520 --> 00:02:19,760 GPUZ, the 6990 reports as running at 31 00:02:16,480 --> 00:02:21,520 16x. And while that may be true because 32 00:02:19,760 --> 00:02:26,959 it's running internal Crossfire where each GPU is getting 16x bandwidth from 33 00:02:24,480 --> 00:02:32,160 the uh from the lane spplitter that's on the PCB 34 00:02:29,239 --> 00:02:37,280 itself. The actual lane splitter itself is only 35 00:02:33,560 --> 00:02:39,040 getting if we look here at the GTX 580. 36 00:02:37,280 --> 00:02:44,720 So you can see that the actual bandwidth to the slot is only 8x because it is 37 00:02:42,080 --> 00:02:52,040 correctly split at this time. So my benchmark results are 38 00:02:48,519 --> 00:02:56,080 3,312 3D marks. So we have seen 39 00:02:52,040 --> 00:02:59,200 a difference in performance between 16x 40 00:02:56,080 --> 00:02:59,200 and 8x 41 00:02:59,640 --> 00:03:08,840 312. Okay, very small, very small. And I 42 00:03:03,280 --> 00:03:11,200 will be back with PCIe 4X results very 43 00:03:08,840 --> 00:03:17,200 shortly. So at the end of the day, this video becomes more about how if you 44 00:03:13,680 --> 00:03:20,239 internally bottleneck a card um 45 00:03:17,200 --> 00:03:22,640 according to the computational resources 46 00:03:20,239 --> 00:03:28,159 located on the card that the amount of PCI Express bandwidth you supply it with 47 00:03:25,200 --> 00:03:32,799 is actually going to make very little difference in terms of performance. Now, 48 00:03:30,239 --> 00:03:37,200 something to bear in mind too about this particular testing setup today. You can 49 00:03:34,640 --> 00:03:40,799 see I had to nudge my motherboard over a little bit to get the uh 6T90 to fit 50 00:03:39,200 --> 00:03:47,440 into that bottom slot on my tech station. But so, I've got it in the PCIe 51 00:03:43,959 --> 00:03:50,080 4x slot. Now, think about it this way. 52 00:03:47,440 --> 00:04:00,400 Basically, I've got two GPUs. I have on a 6990, I pretty much have two 6970 53 00:03:54,080 --> 00:04:00,400 GPUs. Okay? So, so bear with me here. 54 00:04:00,760 --> 00:04:08,040 So, by the comparison I did the other day where I was comparing 55 00:04:05,799 --> 00:04:13,439 16x6 and 8x8x SLI, this is basically running it 56 00:04:11,599 --> 00:04:19,400 on this motherboard, this card in 16X mode is pretty much like running two 57 00:04:15,840 --> 00:04:24,520 cards, two high-end single GPUs at 58 00:04:19,400 --> 00:04:28,560 8x8x, 4x4x in the 8x slot, and then at 59 00:04:24,520 --> 00:04:29,840 2x 2x in that 4x slot at at the very 60 00:04:28,560 --> 00:04:36,000 bottom that that's essentially the amount of bandwidth we have available 61 00:04:31,680 --> 00:04:37,520 per GPU and we still see very very 62 00:04:36,000 --> 00:04:42,240 little fluctuation in terms of the overall score. So, what I may have to do 63 00:04:39,040 --> 00:04:44,960 in the coming uh next little while is do 64 00:04:42,240 --> 00:04:51,840 an updated video about this where I find a slightly less uh GPU speed 65 00:04:49,280 --> 00:04:55,840 bottlenecked benchmark and uh demonstrate maybe more of a more of a 66 00:04:54,000 --> 00:05:00,000 typical or worst case scenario for how much the PCI Express bandwidth affects 67 00:04:58,000 --> 00:05:02,639 single card performance. So, thank you for checking out this little episode of 68 00:05:01,360 --> 00:05:07,880 Linus Tech Tips. Don't forget to subscribe for more unboxings, reviews, and other computer videos.