this post was submitted on 19 Jun 2024
714 points (98.6% liked)

Technology

59106 readers
3944 users here now

This is a most excellent place for technology news and articles.


Our Rules


  1. Follow the lemmy.world rules.
  2. Only tech related content.
  3. Be excellent to each another!
  4. Mod approved content bots can post up to 10 articles per day.
  5. Threads asking for personal tech support may be deleted.
  6. Politics threads may be removed.
  7. No memes allowed as posts, OK to post as comments.
  8. Only approved bots from the list below, to ask if your bot can be added please contact us.
  9. Check for duplicates before posting, duplicates may be removed

Approved Bots


founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
[–] Spedwell@lemmy.world 6 points 4 months ago (1 children)

Right concept, except you're off in scale. A MULT instruction would exist in both RISC and CISC processors.

The big difference is that CISC tries to provide instructions to perform much more sophisticated subroutines. This video is a fun look at some of the most absurd ones, to give you an idea.

[–] barsoap@lemm.ee 2 points 4 months ago* (last edited 4 months ago)

ARM prominently has an instruction to deal with Javascript. And RISC-V will have those kinds of instructions, too, they're too useful, saving a massive amount of instructions and cycles and the CPU itself doesn't really need any logic added, the insn decoder just has to be taught a bit pattern and which microops to emit, the APUs already can do it.

What that instruction will never do in a RISC CPU though is read from memory.

On the flipside, some RISC-V macroops are CISC, fusing memory access and arithmetic. That's an architecture detail, though, only affecting code to the degree of "if you want to do this stuff, and want it to run faster on some cores, put those instructions in this exact sequence so the core can spot and fuse them).