Re:RISC-V announces first new specifications of 2022 adding ...
by monocasa on Tuesday June 21, 2022 @02:35PM
(#31827408)
If you take a step back and define the concept in question as
'cores that have pipeline stages that can block the pipeline as they work their way through a core local state machine (whether that state machine is encoded in a table form via microcode or via a sea of logic)', then there's quite a few on the low end for multiply support. Remember that RV32EM is competing with Cortex-M0, which can get down to 12k gates when it has an iterative, bit-serial multiply.
Re:RISC-V announces first new specifications of 2022 adding ...
by bpye on Tuesday June 21, 2022 @03:16PM
(#31827917)
Whilst true for multiply, divide is considerably more complex. You have to step up to the M3 to get a divide instruction on the ARM side. This is why the new Zmmul is valuable over the existing M extension.
Re:RISC-V announces first new specifications of 2022 adding ...
by monocasa on Tuesday June 21, 2022 @03:24PM
(#31828028)
Agreed, but the point was that state machine, iterative, blocking pipeline stages are pretty common even in RISC cores, including particularly ascetic RISC-V and ARM cores. But I can get how at ~12k gates you don't even want the slowest iterative divide unit.
Maybe you’d count SERV?