Friday, April 17, 2015

Rant (and offtopic) AMD 16 way Zen core?

No way! This piece of news on Fudzilla is silly at best.

At least not with all combined. And this is not because I dream a conspiracy or I don't like AMD. In fact my last hardware I bought was AMD (yet a GPU, but it was only because I didn't need a CPU for a long time)

Let's clarify why, there is no area in itself on CPU even with AMD dense libraries that is used for GPU to fit all. There are CPUs with very good packing of transistors and have a very similar specification with this new future CPU, it is using even a worse litography (22 nm compared with the 14 nm FinFET for AMD case) and this is a Xeon CPU.

But the worse part in my mind is that even the specifications are in the reachability of the smaller transistors the following parts give to me doubts that there will be in 2016 (even in December, the launch date) a full 16 core CPU:
- AMD has no experience with 16 core, their previous designs were 8x2 cores designs, not to say that they are not impressive, but maybe the tradition of late and underwhelming delivery of AMD (likely because it lost some of key engineers when the company shrunk) makes me skeptical that they have a good working prototype already (as Zen is expected to be launched in 1 year from now, it requires at least some prototypes to be made with some time before, AMD Carizzo for instance had good CPUs sampling around 6 months ago and is still not launched)
- 14 nm FinFET is not necessarily that good compared with Intel's 14 nm, because some parts of the interconnect are using a bigger process.
- the design is an APU and in general CPU cache and APUs do require a lot of CPU real estate. You cannot scale infinitely an CPU to all directions because the heat for instance can break it really fast

At last, but not at least, is: who cares? The benchmarks and real numbers in applications are what matter. AMD Bulldozer is a great CPU, especially if you count the core count, and the initial real life delivery was bad, really bad. When Intel Haswell CPUs were launched, you can assume realistically that 2 AMD cores (or one "module") of AMD runs basically in the same as 1 Intel Core.

Even here on the blog, a desktop CPU (AMD 6 core - or 3 cores with 2 modules - read into comments) can run maybe a bit worse with 1 core and probably it will run very similar with a  dual core laptop with similar generations (i5M first gen vs AMD 6150 BE desktop),

I am sure that no AMD engineer is here, but what it looks to me is that the best architectures AMD have are probably Puma/Jaguar based (which themselves I think are based to a simplified Phenom cores) which run inside tablets/slow laptops/consoles. They don't have HSA, but they do run damn well. If there would be a low-power cluster of 2 x 8 cores Pumas, I would likely want a APU like this: it is starved on memory front, but all than this, many algorithms that are CPU intensive are CPU cache friendly, so the CPU will fine on those, and the non-CPU intensives maybe will run fine just because there are many cores to split the workload.

Good luck AMD!

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