WEBVTT 1 00:00:00.000 --> 00:00:00.930 In this lesson, 2 00:00:00.930 --> 00:00:03.540 we're going to talk about "Multi-channel Memory." 3 00:00:03.540 --> 00:00:06.120 Now, multi-channel memory allows a system 4 00:00:06.120 --> 00:00:08.970 to use two different memory modules at the same time 5 00:00:08.970 --> 00:00:12.480 in tandem to increase the performance and throughput. 6 00:00:12.480 --> 00:00:15.330 For example, if I'm using single-channel memory, 7 00:00:15.330 --> 00:00:18.780 this means that I'm using one 64-bit data pathway 8 00:00:18.780 --> 00:00:21.810 or data bus between the processor, the memory controller, 9 00:00:21.810 --> 00:00:23.430 and the RAM modules. 10 00:00:23.430 --> 00:00:26.280 But if I have two different modules and I operate them 11 00:00:26.280 --> 00:00:28.260 in what's known as dual-channel mode, 12 00:00:28.260 --> 00:00:31.770 I can then have two 64-bit pathways working together 13 00:00:31.770 --> 00:00:34.950 giving me essentially a 128-bit pathway. 14 00:00:34.950 --> 00:00:37.470 This interleaving actually gives you increased performance 15 00:00:37.470 --> 00:00:40.020 that actually more than just doubling your speed. 16 00:00:40.020 --> 00:00:41.610 I like to think about it this way. 17 00:00:41.610 --> 00:00:43.050 When you're using interleaving, 18 00:00:43.050 --> 00:00:45.750 let's say you had two horses and they're pulling a cart. 19 00:00:45.750 --> 00:00:48.810 Now each horse might be able to pull 100 pounds by itself, 20 00:00:48.810 --> 00:00:50.700 but working together, those two horses 21 00:00:50.700 --> 00:00:52.890 can actually pull 250 pounds. 22 00:00:52.890 --> 00:00:54.900 Now this is actually more than each one could do 23 00:00:54.900 --> 00:00:56.820 by themselves or adding them together. 24 00:00:56.820 --> 00:00:57.930 And that's really what happens 25 00:00:57.930 --> 00:00:59.400 when we start doing interleaving. 26 00:00:59.400 --> 00:01:00.510 This is the same idea 27 00:01:00.510 --> 00:01:02.730 with the speed of access and interleaving. 28 00:01:02.730 --> 00:01:04.980 Now, when we do this, the sum total of both 29 00:01:04.980 --> 00:01:06.510 can actually access more 30 00:01:06.510 --> 00:01:08.850 than either one could do individually. 31 00:01:08.850 --> 00:01:11.700 So what kind of multi-channel setups might you find 32 00:01:11.700 --> 00:01:12.900 out in the field? 33 00:01:12.900 --> 00:01:15.180 Well, there's really four basic ones. 34 00:01:15.180 --> 00:01:17.580 These are known as single-channel, dual-channel, 35 00:01:17.580 --> 00:01:19.980 triple-channel, and quad-channel. 36 00:01:19.980 --> 00:01:22.590 With single channel, you're using one memory module 37 00:01:22.590 --> 00:01:24.000 on one bus. 38 00:01:24.000 --> 00:01:26.310 So if you have a 64-bit data bus, 39 00:01:26.310 --> 00:01:28.830 that means you're going to have 64-bits being sent 40 00:01:28.830 --> 00:01:31.890 to and from the processor at every clock cycle. 41 00:01:31.890 --> 00:01:33.450 If you're using dual channel, 42 00:01:33.450 --> 00:01:35.370 this is going to require two memory modules 43 00:01:35.370 --> 00:01:37.560 and two memory slots on the motherboard 44 00:01:37.560 --> 00:01:39.270 that are working in tandem together 45 00:01:39.270 --> 00:01:40.920 and interleaving themselves. 46 00:01:40.920 --> 00:01:44.340 This takes those two 64-bit pathways and combines them 47 00:01:44.340 --> 00:01:47.280 to give you essentially 128-bits of data 48 00:01:47.280 --> 00:01:49.890 being sent per transfer every single clock cycle, 49 00:01:49.890 --> 00:01:52.080 instead of only 64. 50 00:01:52.080 --> 00:01:53.160 Now, in addition to this, 51 00:01:53.160 --> 00:01:54.990 you might move up to triple-channel. 52 00:01:54.990 --> 00:01:56.070 And with triple-channel, 53 00:01:56.070 --> 00:01:58.620 you're going to use three memory modules and three slots 54 00:01:58.620 --> 00:02:01.020 all in tandem with this interleaving notion 55 00:02:01.020 --> 00:02:04.200 to give you up to 192-bits of data transfer 56 00:02:04.200 --> 00:02:07.230 over that path to the 64-bit processor. 57 00:02:07.230 --> 00:02:09.330 And finally, we have quad-channel. 58 00:02:09.330 --> 00:02:12.030 Now with quad channel, we're going to take four memory modules 59 00:02:12.030 --> 00:02:14.850 and four slots and have them all working in tandem 60 00:02:14.850 --> 00:02:17.790 to give us 256-bits of data transfer 61 00:02:17.790 --> 00:02:20.610 on each clock cycle to and from the processor 62 00:02:20.610 --> 00:02:22.320 from our memory units. 63 00:02:22.320 --> 00:02:25.020 Now, when you're configuring dual-channel, triple-channel, 64 00:02:25.020 --> 00:02:26.010 or quad-channel, 65 00:02:26.010 --> 00:02:28.950 it's important to consult your motherboards manual first. 66 00:02:28.950 --> 00:02:31.410 This is because every motherboard is a little bit different 67 00:02:31.410 --> 00:02:32.940 in how they set them up. 68 00:02:32.940 --> 00:02:34.800 For instance, just because your motherboard 69 00:02:34.800 --> 00:02:37.920 has four slots doesn't mean it supports quad-channel. 70 00:02:37.920 --> 00:02:40.410 It may only support single-channel and dual-channel. 71 00:02:40.410 --> 00:02:43.140 And you wouldn't know that unless you check your manual. 72 00:02:43.140 --> 00:02:44.820 Generally, when you're looking at the slots 73 00:02:44.820 --> 00:02:46.500 on your motherboard, they're going to be labeled 74 00:02:46.500 --> 00:02:51.500 as zero, one, two, three, and four, or A0, A1, B0, B1 75 00:02:52.290 --> 00:02:54.180 if we're doing them in banks. 76 00:02:54.180 --> 00:02:56.250 Again, it's important to check your documentation 77 00:02:56.250 --> 00:02:58.140 on your motherboard to know which slots 78 00:02:58.140 --> 00:03:00.480 to put your memory in, especially if you want to be operating 79 00:03:00.480 --> 00:03:03.420 in something other than a single-channel configuration. 80 00:03:03.420 --> 00:03:04.560 Another thing to keep in mind 81 00:03:04.560 --> 00:03:06.570 when using multi-channel configurations 82 00:03:06.570 --> 00:03:08.400 is that it is considered a best practice 83 00:03:08.400 --> 00:03:12.570 to use the same model make speed and throughput of memory 84 00:03:12.570 --> 00:03:14.520 in all of the slots that are going to be a part 85 00:03:14.520 --> 00:03:17.280 of that same multi-channel working together. 86 00:03:17.280 --> 00:03:19.710 For example, if you're going to have four slots 87 00:03:19.710 --> 00:03:21.330 on your motherboard, and you're going to be operating 88 00:03:21.330 --> 00:03:23.070 in dual-channel configuration, 89 00:03:23.070 --> 00:03:25.290 and so you're going to use two of those slots together, 90 00:03:25.290 --> 00:03:26.910 you want to make sure that the memory module 91 00:03:26.910 --> 00:03:30.300 in both slots is the same size, such as eight gigabytes 92 00:03:30.300 --> 00:03:33.840 or 16 gigabytes, and the same speed such as 16,000 93 00:03:33.840 --> 00:03:36.990 or 32,000 megabytes per second, to ensure 94 00:03:36.990 --> 00:03:38.880 that you're not going to have any compatibility issues 95 00:03:38.880 --> 00:03:41.130 or errors pop up later on. 96 00:03:41.130 --> 00:03:43.440 So when it comes to multichannel memory, 97 00:03:43.440 --> 00:03:46.890 remember, you can have multiple modules working together 98 00:03:46.890 --> 00:03:49.110 to give you faster speeds in addition to having 99 00:03:49.110 --> 00:03:50.820 a higher overall amount of memory 100 00:03:50.820 --> 00:03:52.440 that you can use for storage. 101 00:03:52.440 --> 00:03:54.270 This is an important consideration to have. 102 00:03:54.270 --> 00:03:56.580 And so if your motherboard does support multi-channel 103 00:03:56.580 --> 00:03:58.920 and you are already going to be using multiple modules, 104 00:03:58.920 --> 00:04:01.020 you might as well take advantage of the increased speed 105 00:04:01.020 --> 00:04:02.700 that you can get by using multi-channel 106 00:04:02.700 --> 00:04:04.113 as a configuration feature.