1 00:00:00,000 --> 00:00:05,180 Cores, cores, cores. Whether you're an Intel fan or an AMD diehard, 2 00:00:05,180 --> 00:00:08,280 both of the big PC chip makers are trying to sell you 3 00:00:08,280 --> 00:00:11,360 on the idea that you need as many cores as possible. 4 00:00:11,360 --> 00:00:14,920 But wait a second, why can't we just have CPUs 5 00:00:14,920 --> 00:00:18,480 that have one lone super powerful core? 6 00:00:18,480 --> 00:00:22,040 Wouldn't that be a lot more straightforward? I mean, think about it. 7 00:00:22,040 --> 00:00:27,880 Those old school parallel ports that we used to use for printers carried lots of data streams at once, 8 00:00:27,960 --> 00:00:34,200 but they were actually very slow. Meanwhile, USB ports only handle one data stream 9 00:00:34,200 --> 00:00:39,600 at a time, but they're very fast. Couldn't we just apply that same idea to CPUs? 10 00:00:39,600 --> 00:00:44,560 To answer, we spoke with Eric Jihon, Intel's CPU SOC architecture lead, 11 00:00:44,560 --> 00:00:49,720 and we'd like to thank him along with Thomas Hannaford and Ben Benson for helping us out with this episode. 12 00:00:49,720 --> 00:00:53,320 As it turns out, a single core is certainly capable 13 00:00:53,320 --> 00:00:57,320 of juggling multiple programs at one time. This is done by scheduling, 14 00:00:57,320 --> 00:01:01,760 where each clock cycle of the CPU, and there are billions of those per second, 15 00:01:01,760 --> 00:01:06,840 is assigned to execute instructions from a certain program or multiple programs. 16 00:01:06,840 --> 00:01:12,760 Scheduling can be done by the operating system, or more optimally, it can be handled by the CPU's hardware. 17 00:01:12,760 --> 00:01:16,120 For example, simultaneous multi-threading or SMT 18 00:01:16,120 --> 00:01:21,000 has been with us since the early 2000s and actually makes your operating system see 19 00:01:21,000 --> 00:01:24,760 one physical core as two logical cores. 20 00:01:24,800 --> 00:01:28,160 With SMT then, the operating system will always make sure 21 00:01:28,160 --> 00:01:31,440 that each physical core has two instruction threads 22 00:01:31,440 --> 00:01:36,960 to work on so that if a single thread stalls, because the CPU has to wait for additional data, 23 00:01:36,960 --> 00:01:40,600 the CPU core can still work on the other thread. 24 00:01:40,600 --> 00:01:45,520 But even with SMT, scheduling still has inefficiencies. 25 00:01:45,520 --> 00:01:49,440 Each core can still handle only so many instructions per clock cycle, 26 00:01:49,440 --> 00:01:53,240 and if you're trying to run a ton of programs or processes, 27 00:01:53,240 --> 00:02:00,080 the whole scheduling paradigm can become overwhelmed, meaning that adding a second or third or fourth core 28 00:02:00,080 --> 00:02:05,760 can help remove the reliance on the scheduler and allow the CPU to actually do more work. 29 00:02:05,760 --> 00:02:09,280 But the fact that scheduling is an imperfect solution 30 00:02:09,280 --> 00:02:12,720 isn't the only reason that we can't just have one big core. 31 00:02:12,720 --> 00:02:16,240 You also have to think about how much CPUs cost. 32 00:02:16,240 --> 00:02:19,240 Higher end chips are already expensive enough, 33 00:02:19,240 --> 00:02:23,360 but if you tried to consolidate a modern, say, eight core chip 34 00:02:23,360 --> 00:02:27,640 into one big core, the price tag would be even higher. 35 00:02:27,640 --> 00:02:34,000 You see, in modern CPU fabrication, if you have one core that's bad due to a manufacturing defect, 36 00:02:34,000 --> 00:02:40,080 you can just disable it at the factory and then sell that chip as a model with fewer cores. 37 00:02:40,080 --> 00:02:43,440 But if you had one massive core and it was defective, 38 00:02:43,440 --> 00:02:49,600 you'd have to throw the whole thing away, meaning more waste and higher costs for the consumer. 39 00:02:49,600 --> 00:02:52,960 There's also the consideration of how you link up a CPU 40 00:02:52,960 --> 00:02:56,640 to the rest of your PC. A multi-core CPU is set up 41 00:02:56,640 --> 00:03:00,040 so that each core has its own connection or fabric. 42 00:03:00,040 --> 00:03:04,680 That gives it access to memory. As you make these fabrics wider and faster, 43 00:03:04,680 --> 00:03:09,240 it becomes more and more difficult to make a fabric that has the same signal integrity 44 00:03:09,240 --> 00:03:12,280 as the smaller ones that were designed for multi-core chips. 45 00:03:12,280 --> 00:03:16,120 But beyond all of these concerns regarding the CPU itself, 46 00:03:16,120 --> 00:03:20,440 the way we use computers these days really tilts the equation in favor 47 00:03:20,440 --> 00:03:26,720 of having multi-core processors. Although back in the days of Windows 95 and even XP, 48 00:03:26,720 --> 00:03:31,800 you could get away with a single core CPU. Modern versions of Windows are often running 49 00:03:31,800 --> 00:03:35,920 hundreds of processes and thousands of threads at once. 50 00:03:35,920 --> 00:03:39,080 And because PCs are such general-purpose machines 51 00:03:39,080 --> 00:03:44,560 that need to be able to adapt to a wide variety of workloads, it's better to have multiple cores 52 00:03:44,560 --> 00:03:48,880 rather than just hoping that your applications will be optimized enough to take advantage 53 00:03:48,880 --> 00:03:53,240 of one big single core, especially as it's becoming more and more common 54 00:03:53,240 --> 00:03:58,720 for programs and even games to actually be able to take advantage of more than one core. 55 00:03:58,720 --> 00:04:01,960 But there's one alternative that we didn't really talk about. 56 00:04:01,960 --> 00:04:05,240 If you want one huge core, you could just forget about CPUs 57 00:04:05,240 --> 00:04:09,680 and go cut open an avocado. That would solve your problem. 58 00:04:09,680 --> 00:04:14,480 And you wouldn't be hungry anymore. Thanks for watching. Leave a like or a dislike depending how you felt. 59 00:04:14,480 --> 00:04:19,080 Check out our other videos and leave a comment if you have a suggestion for a future fast as possible.