On: RISC-V Pushes into the Mainstream

[audunw]

Dead simple base ISA and easily extensible means it's an obvious choice if you want a custom processor with your own custom instructions.

Scalable so the same ISA (with/without certain extensions) can be used from the smallest microprocessor to high end CPUs.

Compressed instructions gives very high code density (and unlike ARM Thumb doesn't require weird mode switching and is available for 64-bit ISA)

It's not the first popular open ISA. There was OpenRISC before it, but it was fatally flawed (branch delay slots). So RISC-V is arguably the first good popular open ISA.

[erk__ → audunw]

There is also OpenPOWER (under the Linux foundation) which I assume is also good?

Or is RISC-V stictly better than it?

[panick21_ → erk__]

OpenPOWER simply wasn't open, it was simply marketing. Only years after RISC-V started to grow did they change their licensing.

RISC-V is more modular and and by now has far more support behind it.

[classichasclass → panick21_]

OpenPOWER is also an open, royalty-free ISA. You're right that PowerPC and Power ISA didn't start open, but they weren't called OpenPOWER.

[panick21_ → classichasclass]

Even when it was called OpenPOWER it was not as open as RISC-V. Its only much later that it became so.

[classichasclass → erk__]

I have several OpenPOWER systems, including the POWER9 I use as my usual desktop. Besides IBM and other server manufacturers like Tyan and Wistron, you can get them as Raptor workstations and servers.

If you want an OpenPOWER design to play with, look at Microwatt ( https://github.com/antonblanchard/microwatt ) which is complete enough to boot Linux.