
Alibaba Reports Their XT910 RISC-V Core to Be Faster Than an Arm Cortex-A73 - rbanffy
https://www.phoronix.com/scan.php?page=news_item&px=Alibaba-XT910-RISC-V-Speed
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bArray
It's impressive. But there's a few things I want to see:

1\. CPU performance over power consumption and heat dissipation. The A73
pushes for power efficiency, how does it perform in that arena [1]?

2\. We've seen "experimental results" from hardware manufacturers before,
let's see them independently verified. Those numbers could be margin-of-error
[2].

3\. Are those tests single or multi-core performance? If it has more cores and
only just about edges ahead, that's not so impressive.

4\. Does it need cooling? If not, how long can it sustain performance without
throttling? That'll surely limit applications if so.

[1]
[https://en.wikipedia.org/wiki/ARM_Cortex-A73](https://en.wikipedia.org/wiki/ARM_Cortex-A73)

[2] [http://3s81si1s5ygj3mzby34dq6qf-wpengine.netdna-
ssl.com/wp-c...](http://3s81si1s5ygj3mzby34dq6qf-wpengine.netdna-ssl.com/wp-
content/uploads/2020/08/Alibaba-and-A73.png)

~~~
bullen
I would add, at what volume will it be produced? Prices can only go down if
volume is high.

Also memory speed (both Hz and cache structure) is much more of a bottleneck
than CPU clock. Specially with 16 cores!

2 Gflops/watt is the peak of electric transistor CPUs, if they come close to
that; with a volume close to Raspberry 4 and use DDR4 memory with ample cache
they might have a shoot at server cluster competition.

They will need many years of improving the software stack though, so they have
a long uphill battle waiting.

The trick and fallacy of these days of non improving electronics is to aim for
the stars (12nm of what) to get that last market share before saturation.

After that planned obsolescence and fragile 5-7nm chips will flood the market.
Finally the chips will probably be manufactured for peak performance and
longevity but they wont be sold, only rented!

About cooling, the right heatsink is the solution: I found these for my
Raspberry 4's, AFAIK they are the most compact stackable passive cooling for
peak 2Gflops/watt under 10 watts in existence:
[http://move.rupy.se/file/pi_4.jpg](http://move.rupy.se/file/pi_4.jpg)

~~~
bArray
> Also memory speed (both Hz and cache structure) is much

> more of a bottleneck than CPU clock. Specially with 16

> cores!

Very good point! Packing more cores onto a die is not enough... Again it would
be good to see if those benchmarks were single or multi-core performance.

> They will need many years of improving the software stack

> though, so they have a long uphill battle waiting.

Yeah... Getting kernel support, etc, takes some time. They'll also probably
want to build out some dev board platform if they haven't already.

> Finally the chips will probably be manufactured for peak

> performance and longevity but they wont be sold, only

> rented!

I see it going either way, either cost per chip will become so low that they
become an expendable product with a short life span, or the cost of perfecting
them rises so high they are rented. Somehow the rented market for CPUs seems
less likely, a release from your competitor could see your entire stock become
un-rentable.

> About cooling, the right heatsink is the solution

Maybe, but you're not putting a passive cooler on solutions that go much
higher than 10 watts at full chap. Assuming these cores match the ARM cores
(power consumption and computation), they have double the number of them,
therefore probably double the heat output. In reality it's probably even worse
as the cores act as insulators to one another.

In 2+ years, let's see how they perform in the market. I guess irrespective of
how good they are, the Chinese market is stuck with them unless tensions
improve.

------
fomine3
More detailed article: [https://www.nextplatform.com/2020/08/21/alibaba-on-
the-bleed...](https://www.nextplatform.com/2020/08/21/alibaba-on-the-bleeding-
edge-of-risc-v-with-xt910/)

~~~
xster
Is this actually helpful in the end?

> The XT910 supports RISC-V 0.7.1 Vector Extension, includes a vector engine
> for AI acceleration and is based on 12 nanometer FinFET processes from
> Taiwan Semiconductor Manufacturing Corp.

In other words, it's still one Trump order away from not being able to
manufacture it.

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FullyFunctional
This story is going around like a firestorm, but reality is a bit different.
They quote Dhrystones and CoreMark, both of which are terrible and should be
avoided. By their own admission in Slack comments: "We have run the
SPECInt2006 benchmark with -O2 compilation option. The performance of XT-910
is 6.11 SPECInt/GHz, which is ~10% lower than the 6.75 SPECInt/GHz delivered
by Cortex-A73."

------
ncmncm
As a side note, I always wonder what is the difference in meaning between "as
of yet", and "yet".

Suspecting it means exactly as much as "currently" usually does.

~~~
tyingq
Probably (badly) derived from the more correct "as of Tuesday", "as of
December 2019", etc. It's a useful phrasing against an actual value.

------
olliej
I mean also worth noting that the arm cortex systems are the fastest anyway -
that’s thing like snap dragon, a-series, etc

~~~
fomine3
Fastest arm core is Apple's one.

Also Cortex-A73 even isn't fastest in Cortex series anymore. It was used for
example Snapdragon 835 (with some modification). Latest Snapdragon 865 uses
Cortex-A77 (with some modification) that is significantly faster than A73.

~~~
olliej
Wait, I thought snap dragon was a full in-house design? Have I been wrong all
this time?

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abdulla
My understanding is that they used to be, now they're all Cortex derivatives:
[https://en.wikipedia.org/wiki/Kryo#Kryo_5xx_Series](https://en.wikipedia.org/wiki/Kryo#Kryo_5xx_Series)

~~~
olliej
thanks!

