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Comment by marcosdumay | Hacker News Reader

The one question I have about asynchronous chips since I studied them at my undergrad is: How does one sell them?

Selling a clocked processor is easy. One tests for a finite set of clock speeds, and marks by the fastest one that works. People buy the chip, and run at the tagged clock getting a predictable performance.

Now, make it a batch of asynchronous processors. Each chip you make will have a different performance - one will add some floats faster, another will fetch run faster (but only if the second bit of the address is set), while a third one will shine on integer addition, but completely suck at subtraction (due to a problem in a single transistor).

How does one tag those chips?

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I have an asynchronous CPU cluster on my desk right now (a pair of GA144s). The performance spread isn't actually very dramatic; just a few percent. After all, the foundries aim for consistency so that synchronous devices get good yields.

You can have either consistency or high performance, not both.

Your batch is consistent because the foundry you brought from isn't pushing the envelope for performance. The latest Intel or AMD chips don't have this level of consistency.

Bottom up: Create a suite of tests (you'll need them for development and verification anyway), measure the performance, tag it with a number based on how fast it finished. If more chips support the same set of instructions, talk to the company and release standardised tests which now everyone else will "need" to support.

Top down: It can copy bytes in memory at X MB/s, do AES at Y MB/s, generate RSA keys at Z/s, ...

> Each chip you make will have a different performance [...]

Sure. You can test them and if they benchmark below 95% of the expected numbers, throw them out (or split out and sell cheaper).

The entire problem is that there isn't a single linear measure of performance. It is the same problem one has comparing different CPU designs, but it now applies for every single chip you make.

They can certainly be clustered. But what kind of performance are you buying when you get a $model? Yes, you have another $model on your desk to compare, but the new one does not have the same performance at all. What if the one you already have is a fast one? Then you can not expect the new one to be as fast, and may prefer buying from some other manufacturer.

EDIT: To put it shorter: How do you promise you the chip I'm selling has at least some performance X when I don't have any chip with performance X for you to measure and see what it means?

I don't think that's so much different than what we have right now. Processors have different core counts, different buses, different feature sets, different speeds on those features, and that's still before we get into patching the microcode. Sure, the differences may be in more basic operations, but then we'll just have benchmarks which expose those numbers instead.

No they don't.

When you get to Amazon, and order a i3 $generation, you know exactly how many cores it will have, and what performance each core has. Every single one of those chips with the same tag have the same performance.

To respond to your edit - tell me something I know about. Like I posted before, how many AES blocks can it decode per second. How many many NxM matrices can it multiply per second. How quickly does it match in a kd-tree. Even tell me that it runs quake at x fps etc. An abstract number (overall performance is 9001) is actually what the customer cares about the least.

I'm going to know what my workload is, or what to compare it to. If you don't know what your workload is, then you're likely a general computer use customer and don't have specific requirements.

By benchmarking them, like GeekBench does. And those benchmarks are the only thing interested parties rely on, not the marketed speeds.

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