1 00:00:06,420 --> 00:00:09,300 - [Instructor] Let's talk about some additional RAM features 2 00:00:09,300 --> 00:00:14,300 and I wanna get into multichannel RAM and also ECC. 3 00:00:15,390 --> 00:00:17,310 If you remember, in the previous video, 4 00:00:17,310 --> 00:00:21,870 we talked about the connection between the RAM and the CPU, 5 00:00:21,870 --> 00:00:26,870 and we said that we'll normally have a 64-bits connection, 6 00:00:27,360 --> 00:00:29,790 64-bit bus, which means 7 00:00:29,790 --> 00:00:34,790 that it can transmit eight bytes of data per cycle. 8 00:00:34,920 --> 00:00:39,180 This is the original single channel RAM, 9 00:00:39,180 --> 00:00:43,560 one 64-bit address bus or data channel. 10 00:00:43,560 --> 00:00:48,560 However, what if we were to add additional banks of RAM? 11 00:00:49,290 --> 00:00:51,993 Well, we could add more if we wanted to. 12 00:00:52,950 --> 00:00:56,760 For example, if we added a second bank of RAM, 13 00:00:56,760 --> 00:01:01,760 we would then have an additional 64-bit bus. 14 00:01:04,590 --> 00:01:09,590 This would be known as dual channel 15 00:01:11,400 --> 00:01:13,560 and in a dual channel setup, 16 00:01:13,560 --> 00:01:16,380 the RAM works together and you then 17 00:01:16,380 --> 00:01:20,130 have 128 bits altogether. 18 00:01:20,130 --> 00:01:24,423 So now we're actually sending 16 bytes of data per cycle. 19 00:01:25,380 --> 00:01:27,780 And you could go beyond this if you wanted to. 20 00:01:27,780 --> 00:01:31,740 We could take that RAM and add some more. 21 00:01:31,740 --> 00:01:33,570 If we add a third one, it would be known 22 00:01:33,570 --> 00:01:35,640 as triple channel RAM. 23 00:01:35,640 --> 00:01:38,550 We'd have three channels of RAM altogether, 24 00:01:38,550 --> 00:01:41,613 and then it would be a 192-bit bus. 25 00:01:42,870 --> 00:01:47,760 And on many computers today, you'll have a fourth channel. 26 00:01:47,760 --> 00:01:50,130 So now we have connectivity here. 27 00:01:50,130 --> 00:01:54,030 We have connectivity here, and they all work together. 28 00:01:54,030 --> 00:01:56,790 All these 64-bit buses. 29 00:01:56,790 --> 00:01:59,463 This would be known as quad channel. 30 00:02:00,360 --> 00:02:02,580 And in a quad channel setup, 31 00:02:02,580 --> 00:02:07,560 it comes to 256 bit, which is 32 bytes 32 00:02:07,560 --> 00:02:09,810 of data simultaneously. 33 00:02:09,810 --> 00:02:11,670 So the more channels you use, 34 00:02:11,670 --> 00:02:14,070 if your motherboard can support it, 35 00:02:14,070 --> 00:02:17,550 the more data you can send per second. 36 00:02:17,550 --> 00:02:19,740 Now, in the previous video, 37 00:02:19,740 --> 00:02:23,850 we said that we were using DDR4-2133. 38 00:02:26,040 --> 00:02:27,690 That was the standard. 39 00:02:27,690 --> 00:02:32,690 The name of the PC module was PC4-17000 40 00:02:38,070 --> 00:02:42,420 or 17066, depending on where you buy the module. 41 00:02:42,420 --> 00:02:45,090 But another type of feature 42 00:02:45,090 --> 00:02:49,380 that you might see in RAM is called ECC. 43 00:02:49,380 --> 00:02:53,220 ECC stands for Error Correction Code. 44 00:02:53,220 --> 00:02:58,220 ECC in RAM can detect and correct errors. 45 00:02:59,520 --> 00:03:03,120 Real-time applications might use ECC RAM. 46 00:03:03,120 --> 00:03:06,930 You might see Error Correction Code RAM in servers 47 00:03:06,930 --> 00:03:09,930 and high-power workstations. 48 00:03:09,930 --> 00:03:12,390 And if you're purchasing the RAM, 49 00:03:12,390 --> 00:03:15,510 you would see the difference in the name. 50 00:03:15,510 --> 00:03:19,827 Instead of PC4-17000, in might be called PC4-17000E 51 00:03:21,840 --> 00:03:25,170 and the E meaning Error Correction Code. 52 00:03:25,170 --> 00:03:28,680 When you're using ECC, additional information needs 53 00:03:28,680 --> 00:03:31,680 to be stored and more resources 54 00:03:31,680 --> 00:03:34,923 are used in general on the RAM module. 55 00:03:36,150 --> 00:03:38,430 This RAM is the slowest 56 00:03:38,430 --> 00:03:42,870 and the most expensive of the RAM types out there. 57 00:03:42,870 --> 00:03:47,870 For example, for every 128 bits of data that are stored, 58 00:03:50,820 --> 00:03:54,610 DDR will store an additional eight bits 59 00:03:55,710 --> 00:03:58,743 of data for the Error Correction Code. 60 00:03:59,760 --> 00:04:03,450 If ECC is enabled, whenever the data is read, 61 00:04:03,450 --> 00:04:06,930 the actual data and the ECC data 62 00:04:06,930 --> 00:04:10,440 are read together by the RAM module 63 00:04:10,440 --> 00:04:13,350 and by the memory controller on the CPU. 64 00:04:13,350 --> 00:04:16,290 And so, newer versions of DDR 65 00:04:16,290 --> 00:04:21,290 like DDR4 and DDR5 can repair single bit errors 66 00:04:21,420 --> 00:04:24,720 on any data bits right away. 67 00:04:24,720 --> 00:04:29,430 So that's really important for things like servers. 68 00:04:29,430 --> 00:04:31,200 So make sure that you know 69 00:04:31,200 --> 00:04:36,120 and understand multibank technologies like single channel, 70 00:04:36,120 --> 00:04:38,370 dual channel, and quad channel, 71 00:04:38,370 --> 00:04:43,263 and also understand ECC or Error Correction Code in RAM.