By: Wilco (wilco.dijkstra.delete@this.ntlworld.com), April 9, 2021 1:39 pm
Room: Moderated Discussions
Anon (no.delete@this.spam.com) on April 9, 2021 10:06 am wrote:
> juanrga (nomail.delete@this.juanrga.com) on April 9, 2021 3:44 am wrote:
> > Cortex A72 achieving 4.2GHz on 7HPC:
> >
> > https://fuse.wikichip.org/news/2446/tsmc-demonstrates-a-7nm-arm-based-chiplet-design-for-hpc/
>
> Thanks, very interesting, so:
> 1) 4 A72 cores and 6MB L3 taking 27.28mm², so high performance transistors does indeed are
> a lot less dense, all those claims about small high perf ARM cores are just bullshit;
Which claims exactly? Each Cortex-A72 is just 0.5mm^2 in that die photo, and the 4-core complex with 2MB L2 is 4.9mm^2. A single Zen 3 core is about 4mm^2.
Note TSMC's HP libraries use 7.5 tracks, so they use about 25% more area than the 6T high density cells.
> 2) 1.375V to reach 4.2GHz, Zen 3 reaches 4.9GHz at that voltage, and the last 200MHz
> needed 0.175 extra volts, no way for a CPU like M1 or N1 going much futher than 3GHz.
A72 is old and not designed for 7nm, let alone 4GHz. The reason it is used to qualify new processes is because it is small and has well characterized critical paths. Its fmax won't be the same as completely different microarchitectures.
Wilco
> juanrga (nomail.delete@this.juanrga.com) on April 9, 2021 3:44 am wrote:
> > Cortex A72 achieving 4.2GHz on 7HPC:
> >
> > https://fuse.wikichip.org/news/2446/tsmc-demonstrates-a-7nm-arm-based-chiplet-design-for-hpc/
>
> Thanks, very interesting, so:
> 1) 4 A72 cores and 6MB L3 taking 27.28mm², so high performance transistors does indeed are
> a lot less dense, all those claims about small high perf ARM cores are just bullshit;
Which claims exactly? Each Cortex-A72 is just 0.5mm^2 in that die photo, and the 4-core complex with 2MB L2 is 4.9mm^2. A single Zen 3 core is about 4mm^2.
Note TSMC's HP libraries use 7.5 tracks, so they use about 25% more area than the 6T high density cells.
> 2) 1.375V to reach 4.2GHz, Zen 3 reaches 4.9GHz at that voltage, and the last 200MHz
> needed 0.175 extra volts, no way for a CPU like M1 or N1 going much futher than 3GHz.
A72 is old and not designed for 7nm, let alone 4GHz. The reason it is used to qualify new processes is because it is small and has well characterized critical paths. Its fmax won't be the same as completely different microarchitectures.
Wilco