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1. Vertigo (vertigo@mastodon.social)'s status on Sunday, 19-Nov-2017 19:45:33 EST Vertigo

   Compatibility between ISAs isn't guaranteed due to the different register sizes; however, if you're clever with your coding, you can write multi-ISA code.

   Cross-width compatibility isn't a priority, though, as history shows to make a cross-width-compatible ISA, you need a lot of complex mechanisms in the hardware (defeating its RISC-y nature). It's expected the compiler will paper over the differences.

   Note that x86-64 is also not compatible with x86-32. :) Not even x86 is immune.

   1. clacke (clacke@social.heldscal.la)'s status on Sunday, 19-Nov-2017 19:49:23 EST clacke

      in reply to
      @vertigo That is interesting. When creating an ISA from scratch, what are the argument for not making e.g. RV32 simply a subset of RV128?
      
      That x86 can't be compatible with itself is a given. ;-)