Update:

> Power ISA 3.1B spec released as of September 2021.

Power ISA 3.1C spec released today:

https://files.openpower.foundation/s/9izgC5Rogi5Ywmm/download/OPF_PowerISA_v3.1C.pdf
https://openpowerfoundation.org/specifications/isa/

Update:

> it's now actually announced to be another CPU called S1 by a
> chip design company called Solid Silicon

Solid Silicon has joined the OpenPOWER Foundation as platinum member:
https://openpowerfoundation.org/members/solidsilicon/

...and it has raised 100,000 USD in a funding round in February:
https://www.crunchbase.com/organization/solid-silicon/company_overview/overview_timeline

Thanks for sharing @Andreas_Wolf!

Good to hear news from Solid Silicon S1! This will be the CPU powering Raptors upcoming Blackbird II & Talos III series (klick).

PCIe 5.0, DDR5 RAM, SMT-4, Bi-Endian, 32/64bit does not sound shabby either. Also looks like Power ISA 3.1C does not deprecate any features over the POWER9 so it should run G4/G5/POWER9 built code just fine.

> Solid Silicon S1 […] will be the CPU powering Raptors upcoming
> Blackbird II & Talos III series (klick).

Yes, see comment #240 :-)

> looks like Power ISA 3.1C does not deprecate any features over the
> POWER9 so it should run G4/G5/POWER9 built code just fine.

I'm not sure if S1 will implement 3.1C or an older/newer specification. What we know at least is that Power11 will necessarily implement the same ISA spec as Power10 (see comment #248), which should be 3.1B.

Update:

> Solid Silicon has joined the OpenPOWER Foundation as platinum member: [...]

Today's press release reveals that the CTOs of Raptor CS and Solid Silicon are one and the same Pearson ;-)