By: Wilco (wilco.dijkstra.delete@this.ntlworld.com), April 8, 2021 8:14 am
Room: Moderated Discussions
none (none.delete@this.none.com) on April 8, 2021 6:47 am wrote:
> anon2 (anon.delete@this.anon.com) on April 8, 2021 2:08 am wrote:
> > none (none.delete@this.none.com) on April 8, 2021 1:53 am wrote:
> > > anon2 (anon.delete@this.anon.com) on April 8, 2021 1:16 am wrote:
> > > [...]
> > > > Wrong. It's always been about performance primarily.
> > > >
> > > > > The tax is about how a better
> > > > > ISA like A64 allows using less transistors than x86 to do the same work. So you can achieve
> > > > > the same performance on a smaller size or achieve more performance using the same size,
> > > > > or a combination of both: e.g. ~10% higher performance and ~10% smaller design.
> > > > >
> > > > > If you read the quote given. TX3 gets a similar performance with a 20 or 30% smaller size.
> > > >
> > > > It's about performance lol, don't try to weasel your way out of it. Of course performance is
> > > > also related to size in some ways, so transitively they are related. But you came out like a
> > > > moron and blurted out x86 tax is not about performance, as though that somehow addressed my tongue
> > > > in cheek quip any better than your dishonest and stupid comparison of shipping cores.
> > > >
> > > > The x86 tax was always "about" performance. Sorry to break it to you. It was
> > > > about performance when RISCs were taking performance crowns. It was about performance
> > > > when Intel couldn't match ARM performance in smartphone space.
> > >
> > > In the context of smartphone, the tax was clearly about efficiency, not about performance.
> >
> > Performance/watt, yes of course.
> >
> > Not size.
>
> You were talking about performance primarily, so I just wanted to add another dimension.
> And there's a relation between size and power consumption (though Intel and AMD have been
> getting better at clock and power gating).
>
> I think what people call the x86 tax is more complex than a single thing, size or
> performance.
Absolutely, it's a lot more than "a little more complex decode" as people often incorrectly claim. Having to use desktop cores in servers is a result of x86 complexity. Even AVX-512 can be considered a tax compared to modern alternatives like SVE.
For x86 servers, area is really the largest issue. AMD solved it smartly by using chiplets, but the amount of silicon they need for equivalent performance is even larger. The 8380 die size is claimed to be ~640mm^2. A single core plus 1.5MB L3 slice is around 9.6mm^2 - Neoverse N1 is 1.4mm^2 excluding L3. This is why Ampere Altra (Max) can use a much smaller die and still fit 2-3 times as many cores and end up significantly faster.
Wilco
> anon2 (anon.delete@this.anon.com) on April 8, 2021 2:08 am wrote:
> > none (none.delete@this.none.com) on April 8, 2021 1:53 am wrote:
> > > anon2 (anon.delete@this.anon.com) on April 8, 2021 1:16 am wrote:
> > > [...]
> > > > Wrong. It's always been about performance primarily.
> > > >
> > > > > The tax is about how a better
> > > > > ISA like A64 allows using less transistors than x86 to do the same work. So you can achieve
> > > > > the same performance on a smaller size or achieve more performance using the same size,
> > > > > or a combination of both: e.g. ~10% higher performance and ~10% smaller design.
> > > > >
> > > > > If you read the quote given. TX3 gets a similar performance with a 20 or 30% smaller size.
> > > >
> > > > It's about performance lol, don't try to weasel your way out of it. Of course performance is
> > > > also related to size in some ways, so transitively they are related. But you came out like a
> > > > moron and blurted out x86 tax is not about performance, as though that somehow addressed my tongue
> > > > in cheek quip any better than your dishonest and stupid comparison of shipping cores.
> > > >
> > > > The x86 tax was always "about" performance. Sorry to break it to you. It was
> > > > about performance when RISCs were taking performance crowns. It was about performance
> > > > when Intel couldn't match ARM performance in smartphone space.
> > >
> > > In the context of smartphone, the tax was clearly about efficiency, not about performance.
> >
> > Performance/watt, yes of course.
> >
> > Not size.
>
> You were talking about performance primarily, so I just wanted to add another dimension.
> And there's a relation between size and power consumption (though Intel and AMD have been
> getting better at clock and power gating).
>
> I think what people call the x86 tax is more complex than a single thing, size or
> performance.
Absolutely, it's a lot more than "a little more complex decode" as people often incorrectly claim. Having to use desktop cores in servers is a result of x86 complexity. Even AVX-512 can be considered a tax compared to modern alternatives like SVE.
For x86 servers, area is really the largest issue. AMD solved it smartly by using chiplets, but the amount of silicon they need for equivalent performance is even larger. The 8380 die size is claimed to be ~640mm^2. A single core plus 1.5MB L3 slice is around 9.6mm^2 - Neoverse N1 is 1.4mm^2 excluding L3. This is why Ampere Altra (Max) can use a much smaller die and still fit 2-3 times as many cores and end up significantly faster.
Wilco
