It really doesn't.
I agree an actual open ISA is far preferable, ARM is not much different than x86.
We’d just get a bunch of proprietary cores which might not even be compatible with each other due to extensions. Companies like Qualcomm would have zero incentives to share their designs with anyone.
ARM is not perfect but it at least guarantees some minimal equal playing field.
> Afaik, ARM also licenses ready-to-go cores
Which is the core of Qualcomm’s business. All their phone chips are based on Cortex. Of course ARM has a lot of incentives to keep it that way, hence this while thing.
No different than ARM. Apple has matrix extensions that others don't, for example.
The ecosystem (e.g., Linux and OSS) pressure will strongly encourage compatible subsets however. There is some concern about RISCV fragmentation hell that ARM used to suffer from, but a least in the Linux-capable CPU space (e.g., not highly embedded or tiny), a plethora of incompatible cores will probably not happen.
> Companies like Qualcomm would have zero incentives to share their designs with anyone.
ARM cores are also proprietary. All ARM cores actually, you can't get an architectural license from ARM to create an open source core. With RISCV at least you can make open cores and there are some out there.
But opening the ISA is attacking a different level of the stack than the logic and silicon.
Does "fragmentation hell" refer to Age Old problem of massive incompatibility in the Linux codebase, or the more "modern" problem people refer to which is the problem of device trees and old kernel support for peripheral drivers? Because you can rest assured that this majestic process will not be changed at all for RISC-V devices. You will still be fed plenty of junkware that will require an unsupported kernels with blobs. The ISA isn't going to change the strategy of the hardware manufacturers.
Everyone has more or less the same access to relatively competitive Cortex and Neoverse cores. As ARM’s finances show that’s not a very good business model so it’s unlikely anyone would do that with RISC-V.
You can make opensource cores, but nobody investing massive amounts of money/resources required to design high end CPUs will make them open source. The situation with ARM is of course not ideal but at least the playing field is somewhat more even.
And yet, that's what linux did in 1991- they shared the code, lowering the cost of buying an operating system. I wouldn't say there is zero incentive, but it certainly lowers the incentive without a profitable complementary hardware implementation that can be sold for less than the proprietary isa when there is a royalty free license allows the manufacturer/fab designer "mask rights" to get a small margin within the difference of the foundry/ISA proprietary core competitor.
In segments where chips are almost an interchangeable commodity and the R&D cost might be insignificant relative to manufacturing/foundry it would make a lot more sense.
Not anymore, M4 supports ARM SME instead.
Even if Qualcomm makes their own RISC-V chips that are somehow incompatible with everyone else's, they can't advertise that it's RISC-V due to the branding guidelines. They should know them because they are on the board as a founding top tier member.
IMO we need to question the premises of the current IP ecosystem. Obviously, the principles of open-source are quite the opposite to how ARM licenses IP. (Afaik, ARM also licenses ready-to-go cores, which is very different from what Q is getting.)
It's easy to see how RISC-V avoids the conflict of interest between owning the ISA and licensing specific implementations.