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How did AMD manage to make Threadripper so powerful?!

07 Jan 2019 at 23:50
AMD's Threadripper is a beast. But how can it have 64 cores in a world where 4 cores is the norm?!

Imagine a world where one company rules and dominates every one of its competitors. Well, that world is the world that exists within Silicon Valley between both Intel and AMD.

For years AMD has struggled to make anything that can remotely compete with Intel's power hold over both the market and the consumers. But that's all changing, and whilst they may still have that market and the minds of most consumers, they certainly haven't had the easiest of times in the last few months.

I've been talking a lot about AMD and their recent successes and, in the last few days, I have even gone as far as building The Red Revolution - my next gaming PC - with an AMD Ryzen CPU. The Red Revolution took its name from the fact that AMD's branding is predominantly red and the revolution side being because this is my first AMD powered gaming computer. Ryzen, Threadripper's younger brother, is all about the cores but aims to hit Intel where it hurts, price. My CPU features a whopping 8 cores and 16 threads, this means that it eats through well-designed threaded applications (it can even take advantage of ZPE's own threading potential very well) but it only cost £270. An Intel CPU with 8 cores and 16 threads would be a Core i9 9900K which comes in at around £500 - nearly double the price.

How does AMD achieve this?

So just how does AMD do this? Well, it's not all as simple as one might imagine. Threadripper's 32-core 64-thread 2990WX - the top Threadripper CPU - does not work as one might think. The 2990WX is a 32-core CPU in a non-monolithic package fabricated from four CPU dies in the one package. It's all about pushing more power out of a CPU and bang-for-buck whilst sacrificing physical size and performance-per-watt whilst offering a mediocre improvement overall. But because the improvement AMD has gone for is almost four times that of the Ryzen 2700 that make up those dies, the performance increase is huge. So what does this mean?

AMD's 2990WX is a 32-core CPU. It's not native 32-core though. My Ryzen 2700 is native octa-core though. Native, properly known as a monolithic design, means that there is just one die comprised of the cores. Ryzen connects four CPU dies together. Why is this bad you ask? Well, it's not bad per se. It's just less efficient - but it's the best we can get at this time because of space constraints in CPUs amongst other things like power consumption and heat dissipation (note the current Threadrippers are all using 180W TDPs). I never thought I'd see the day when we move back to multi-die CPUs again. I thought those days were gone with the Intel Core 2 Quad. Again, I'm not saying this is bad, but it comes with issues, in particular heat dissipation.

The first of those issues is connectivity between dies. Between these multiple dies, AMD implements something they call Infinity Fabric - a high speed internal interconnect that is the spine or backbone of the CPU that allows all of the cores (all 32) to communicate both efficiently and quickly.

The second issue is power and TDP. The more physical space required for all those cores and so on, the more heat the CPU produces.

Why hasn't Intel done this yet?

Intel has achieved high core counts on some of their own CPUs, but they are using monolithic designs for these. This means they are focused on getting more cores on a single die than building multiple dies for multiple core designs. This is, ultimately, the preferred way of doing this since it keeps the TDP and power consumption down on these CPUs.

Why has AMD removed Threadripper from their roadmap?

Despite all this and having Intel with their tail between their legs for the first time in a long time, AMD has recently removed their third generation Threadrippers from their roadmap. This means that the continued pressure that AMD have been applying to Intel is almost at a stand still and eventually Intel will catch up again.

So why has AMD done this? Well one reason I have come to believe is that AMD is waiting for fabrication technologies to improve further before releasing the next version of this beast. Potentially, AMD could see huge performance improvements if they were to hold out for a 4nm fabrication (which is most likely next). However, it all seems likely they are sticking to the 7nm fabrication soon to be used in the third generation Ryzen CPUs.

Another reason AMD may be holding out is because they know that they have stock to shift and they need to sell off the Ryzen 2 based Threadrippers.

Whatever AMD's reasoning behind this, I'm sure that they will continue to innovate and shake up Intel's world.

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