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Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

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Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#61

Post by saltcured »

speedgoose wrote: post #21
esafak wrote: post #3

Can't they make a GPU instead? Please save us!

I hope to see dedicated GPU coprocessors disappear sooner rather than later, just like arithmetic coprocessors did.

Aspects of this has been happening for a long time, as SIMD extensions and as multi-core packaging.

But, there is much more to discrete GPUs than vector instructions or parallel cores. It's very different memory and cache systems with very different synchronization tradeoffs. It's like an embedded computer hanging off your PCI bus, and this computer does not have the same stable architecture as your general purpose CPU running the host OS.

In some ways, the whole modern graphics stack is a sort of integration and commoditization of the supercomputers of decades ago. What used to be special vector machines and clusters full of regular CPUs and RAM has moved into massive chips.

But as other posters said, there is still a lot more abstraction in the graphics/numeric programming models and a lot more compiler and runtime tools to hide the platform. Unless one of these hidden platforms "wins" in the market, it's hard for me to imagine general purpose OS and apps being able to handle the massive differences between particular GPU systems.

It would easily be like prior decades where multicore wasn't taking off because most apps couldn't really use it. Or where special things like the "cell processor" in the playstation required very dedicated development to use effectively. The heterogeneity of system architectures makes it hard for general purpose reuse and hard to "port" software that wasn't written with the platform in mind.

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#62

Post by dist-epoch »

johnklos wrote: post #50

One of the biggest problems with CPUs is legacy. Tie yourself to any legacy, and now you're spending millions of transistors to make sure some way that made sense ages ago still works. Just as a thought experiment, consider the fact that the i80486 has 1.2 million transistors. An eight core Ryzen 9700X has around 12 billion. The difference in clock speed is roughly 80 times, and the difference in number of transistor…

If you look at a Zen5 die shots half of the space is taken by L3 cache.

And from each individual core:

- 25% per core L1/L2 cache

- 25% vector stuff (SSE, AVX, ...)

- from the remaining 50% only about 20% is doing instruction decoding

https://www.techpowerup.com/img/AFnVIoGFWSCE6YXO.jpg

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#63

Post by zackmorris »

I hope they design, build and sell a true 256-1024+ multicore CPU with local memories that appears as an ordinary desktop computer with a unified memory space for under $1000.

I've written about it at length and I'm sure that anyone who's seen my comments is sick of me sounding like a broken record. But there's truly a vast realm of uncharted territory there. I believe that transputers and reprogrammable logic chips like FPGAs failed because we didn't have languages like Erlang/Go and GNU Octave/MATLAB to orchestrate a large number of processes or handle SIMD/MIMD simultaneously. Modern techniques like passing by value via copy-on-write (used by UNIX forking, PHP arrays and Clojure state) were suppressed when mainstream imperative languages using pointers and references captured the market. And it's really hard to beat Amdahl's law when we're worried about side effects. I think that anxiety is what inspired Rust, but there are so many easier ways of avoiding those problems in the first place.

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#64

Post by Sohcahtoa82 »

johnklos wrote: post #50

One of the biggest problems with CPUs is legacy. Tie yourself to any legacy, and now you're spending millions of transistors to make sure some way that made sense ages ago still works. Just as a thought experiment, consider the fact that the i80486 has 1.2 million transistors. An eight core Ryzen 9700X has around 12 billion. The difference in clock speed is roughly 80 times, and the difference in number of transistor…

> If a Ryzen takes 1,250 times the transistor for one core, does one core run 1,250 times (even taking hyperthreading in to account) faster than an i80486 at the same clock? 500 times? 100 times?

Would be interesting to see a benchmark on this.

If we restricted it to 486 instructions only, I'd expect the Ryzen to be 10-15x faster. The modern CPU will perform out-of-order execution with some instructions even run in parallel, even in single-core and single-threaded execution, not to mention superior branch prediction and more cache.

If you allowed modern instructions like AVX-512, then the speedup could easily be 30x or more.

> Would we get to 1,250 times faster for 1,250 times the number of transistors? No. Would we get a lot more performance than we get out of a contemporary x86 CPU? Absolutely.

I doubt you'd get significantly more performance, though you'd likely gain power efficiency.

Half of what you described in your hypothetical instruction set are already implemented in ARM.

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#65

Post by kvemkon »

johnklos wrote: post #50

One of the biggest problems with CPUs is legacy. Tie yourself to any legacy, and now you're spending millions of transistors to make sure some way that made sense ages ago still works. Just as a thought experiment, consider the fact that the i80486 has 1.2 million transistors. An eight core Ryzen 9700X has around 12 billion. The difference in clock speed is roughly 80 times, and the difference in number of transistor…

Would be interesting to compare transistor count without L3 (and perhaps L2) cache.

16-core Zen 5 CPU achieves more than 2 TFLOPS FP64. So number crunching performance scaled very well.

It is weird, that the best consumer GPU can 4 TFLOPS. Some years ago GPUs were an order of magnitude and more faster than CPUs. Today GPUs are likely to be artificially limited.

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#66

Post by amelius »

johnklos wrote: post #50

One of the biggest problems with CPUs is legacy. Tie yourself to any legacy, and now you're spending millions of transistors to make sure some way that made sense ages ago still works. Just as a thought experiment, consider the fact that the i80486 has 1.2 million transistors. An eight core Ryzen 9700X has around 12 billion. The difference in clock speed is roughly 80 times, and the difference in number of transistor…

> and now you're spending millions of transistors

and spending millions on patent lawsuits ...

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#67

Post by zozbot234 »

dist-epoch wrote: post #62
johnklos wrote: post #50

One of the biggest problems with CPUs is legacy. Tie yourself to any legacy, and now you're spending millions of transistors to make sure some way that made sense ages ago still works. Just as a thought experiment, consider the fact that the i80486 has 1.2 million transistors. An eight core Ryzen 9700X has around 12 billion. The difference in clock speed is roughly 80 times, and the difference in number of transistor…

If you look at a Zen5 die shots half of the space is taken by L3 cache. And from each individual core: - 25% per core L1/L2 cache - 25% vector stuff (SSE, AVX, ...) - from the remaining 50% only about 20% is doing instruction decoding https://www.techpowerup.com/img/AFnVIoGFWSCE6YXO.jpg

The real issue with complex insn decoding is that it's hard to make the decode stage wider and at some point this will limit the usefulness of a bigger chip. For instance, AArch64 chips tend to have wider decode than their close x86_64 equivalents.

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#68

Post by frankchn »

Bolwin wrote: post #47
Arnavion wrote: post #37

Earlier quoted context omitted.

You want to optimize for specific chips because different chips have different capabilities that are not captured by just what extensions they support. A simple example is that the CPU might support running two specific instructions better if they were adjacent than if they were separated by other instructions ( https://en.wikichip.org/wiki/macro-operation_fusion ). So the optimizer can try to put those instructions…

Wonder if we could generalize this so you can just give the optimizer a file containing all this info, without needing to explicitly add support for each cpu

These configuration files exist (https://llvm.org/docs/TableGen/, https://github.com/llvm/llvm-project/blob/main/llvm/lib/Targ...) but it is very complicated because the processors themselves are very complicated.

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#69

Post by epx »

johnklos wrote: post #50

One of the biggest problems with CPUs is legacy. Tie yourself to any legacy, and now you're spending millions of transistors to make sure some way that made sense ages ago still works. Just as a thought experiment, consider the fact that the i80486 has 1.2 million transistors. An eight core Ryzen 9700X has around 12 billion. The difference in clock speed is roughly 80 times, and the difference in number of transistor…

Aren't 99,99999% of these transistors used in cache?

Re: Top researchers leave Intel to build startup with 'the biggest, baddest CPU'

#70

Post by AnthonyMouse »

johnklos wrote: post #50

One of the biggest problems with CPUs is legacy. Tie yourself to any legacy, and now you're spending millions of transistors to make sure some way that made sense ages ago still works. Just as a thought experiment, consider the fact that the i80486 has 1.2 million transistors. An eight core Ryzen 9700X has around 12 billion. The difference in clock speed is roughly 80 times, and the difference in number of transistor…

Modern CPUs don't actually execute the legacy instructions, they execute core-native instructions and have a piece of silicon dedicated to translating the legacy instructions into them. That piece of silicon isn't that big. Modern CPUs use more transistors because transistors are a lot cheaper now, e.g. the i486 had 8KiB of cache, the Ryzen 9700X has >40MiB. The extra transistors don't make it linearly faster but they make it faster enough to be worth it when transistors are cheap.

Modern CPUs also have a lot of things integrated into the "CPU" that used to be separate chips. The i486 didn't have on-die memory or PCI controllers etc., and those things were themselves less complicated then (e.g. a single memory channel and a shared peripheral bus for all devices). The i486SX didn't even have a floating point unit. The Ryzen 9000 series die contains an entire GPU.

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