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LowLevelProgramming Post #6677 · source on Telegram

The Alarming Efficiency of Modern CPU Instructions

Description

A text-based meme presented as white text on a black background. The text humorously contrasts the simple, foundational instructions of the x86 architecture from 25 years ago (like 'mov', 'add', 'sub') with a fictional, absurdly complex modern instruction. The made-up instruction, 'xtrsprfstcmd', is described hyperbolically as performing multiple arithmetic operations and then escalating to a crude, impossible social interaction, all within a single clock cycle. This meme is a satirical take on the evolution of Complex Instruction Set Computer (CISC) architectures, where individual instructions have become increasingly powerful and abstract. It resonates with low-level programmers, compiler engineers, and hardware enthusiasts who appreciate the joke about the relentless drive for single-cycle performance leading to comically specific and overpowered machine code

Comments

21
Anonymous ★ Top Pick Modern CISC instructions are getting so complex, the next one will probably just be a single 'DO_MY_JOB' instruction, and it will still require three microcode updates to fix the floating-point bug
  1. Anonymous ★ Top Pick

    Modern CISC instructions are getting so complex, the next one will probably just be a single 'DO_MY_JOB' instruction, and it will still require three microcode updates to fix the floating-point bug

  2. Anonymous

    Amazing throughput - until you realize the decoder silently expands xtrsprfstcmd into 47 micro-ops and the reorder buffer hits thermal throttling before your unit tests finish

  3. Anonymous

    The real tragedy is that xtrsprfstcmd still has better documentation than half the AWS services we're using in production

  4. Anonymous

    The real tragedy isn't that modern x86 instructions do everything in one cycle - it's that after 25 years of ISA extensions, we still can't agree on whether it's pronounced 'mnemonic' or 'mnemonic', and Intel's documentation is somehow both 5000 pages long and missing the exact edge case you're debugging at 3 AM

  5. Anonymous

    Every new x86 opcode promises “one cycle” magic - until perf counters whisper 12‑cycle latency, four uops, and a surprise microcode assist

  6. Anonymous

    x86: Instruction complexity so high, it makes enterprise monorepos look like a well-refactored microservice

  7. Anonymous

    That do-everything-in-one-instruction vibe is great - right up until AVX‑512 downclocks the core, the decoder splits it into three uops, and a uop-cache miss makes mov+add look like a RISC superpower

  8. @DerKnerd 1y

    At least it takes your mom to diner like a nice command does

  9. @decide_later 1y

    ARM can easily get intimate with a vector of moms at once in a more efficient and battery-saving way, but you have to better specify how or port it from x86

    1. @yogovelychnystkishka 1y

      Port fails, now ARM dating your dad 😌

      1. @decide_later 1y

        At least it managed to find my dad efficiently as well

      2. @Pancake2x2 1y

        That was arms goal all along

    2. @TheresnoKNOWLEDGEthatISnotPOWER 1y

      Advanced Reciprocal Movement Alternating Reciprocal Motion Lol

    3. @SamsonovAnton 1y

      Doesn't x86 do the same with AVX instructions, as well as RISC-V with Vector instructions, etc.? What is so special about ARM in this regard?

      1. @decide_later 1y

        > What is so special about ARM in this regard? Marketing budget mostly

      2. @purplesyringa 1y

        I mean, realistically, yes, ARM is still worse than x86 for HPC

        1. @tema3210 1y

          Why?

    4. @ZgGPuo8dZef58K6hxxGVj3Z2 1y

      Wait until you realize x86 is a softie under its instructionset too

  10. @VanuxaKR 1y

    What does etc instruction do?)

  11. @purplesyringa 1y

    okay, this is actually funny

    1. @TERASKULL 1y

      found the source https://youtube.com/watch?v=egG5Kraswhc&lc=UgwD9EcHuwoMXoLItKF4AaABAg

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