X86 Needs To Die

ThePrimeTime・2 minutes read

Casey Mortor discussed the evolution and relevance of x86 architecture, emphasizing the need for modern processors to supersede legacy x86 models. The text also delves into key concepts like Von Neumann architecture, pipelining, and the growing popularity of ARM and RISC-V instruction sets over x86 due to their simplicity and efficiency.

Insights

  • The evolution of x86 architecture from 8086 to modern processors has impacted multitasking and memory protection, with x86 CPUs maintaining compatibility with 8086 real mode, influencing software performance comparisons like Node.js vs. Deno.
  • The rise of ARM and RISC-V instruction sets poses a challenge to x86 dominance, with their simplicity and efficiency gaining popularity in various markets, emphasizing the need for improved decoding logic in x86 architecture to enhance efficiency and address the strain on CPUs.

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Recent questions

  • What is x86 architecture?

    x86 architecture is a type of computer architecture that has evolved over time, starting with the 8086 processor and progressing to modern processors. It is known for its compatibility with older software and maintaining features like real mode from the 8086 processor.

  • Why is little-endian and big-endian memory order significant?

    Little-endian and big-endian memory order refer to how bytes are stored in memory. In little-endian, the least significant byte is stored first, while in big-endian, the most significant byte is stored first. This distinction is crucial for data interpretation and communication between different systems.

  • What is the difference between CISC and RISC architectures?

    CISC (Complex Instruction Set Computing) and RISC (Reduced Instruction Set Computing) architectures differ in their approach to instruction sets. CISC processors have complex instructions that can perform multiple operations, while RISC processors have simpler instructions that focus on efficiency and speed.

  • How does pipelining work in CPUs?

    Pipelining in CPUs involves breaking down the execution of instructions into smaller stages that can be processed simultaneously. This allows for better utilization of the CPU's resources and increases overall performance by overlapping different stages of instruction execution.

  • Why are ARM and RISC-V gaining popularity over x86?

    ARM and RISC-V instruction sets are gaining popularity over x86 due to their simplicity, efficiency, and flexibility. ARM dominates in smartphones and single-board computers, while RISC-V is widely adopted in microcontrollers. Their royalty-free nature and ease of use make them attractive options in various markets.

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Summary

00:00

Evolution of x86 Architecture: A Deep Dive

  • Casey Mortor, a programming expert since 1995, delved into CPU workings during a talk.
  • The discussion focused on the necessity for x86 architecture to evolve.
  • An M2 exploit and the debate on x86's relevance were key topics.
  • A technical glitch prompted a switch to Discord for smoother communication.
  • Casey Mortor's expertise lies in performance programming, influencing his interest in x86 architecture.
  • "Chips and Cheese" blog offers in-depth microarchitecture analyses, including x86 discussions.
  • The evolution of x86 architecture from 8086 to modern processors was traced.
  • Register naming conventions in x64 architecture stem from historical CPU lineages.
  • The significance of little-endian and big-endian memory order was explained.
  • x86 CPUs maintain compatibility with 8086 real mode, impacting multitasking and memory protection.

12:50

"Legacy vs. Modern: CPU Performance Comparison"

  • Backwards compatibility in software can often lead to slower performance, as seen in the Node.js vs. Deno comparison where Deno's lack of support for legacy features contributed to its speed.
  • A hypothetical scenario is presented where Node.js is re-implemented on top of Deno, allowing for faster execution by utilizing Deno's efficient features and falling back to slower emulation when necessary.
  • The x64 architecture offers both fast and slow modes, catering to older applications that require legacy support while also providing modern, faster capabilities.
  • The argument is made to retire the legacy of x86 processors and allow modern processors to operate freely.
  • Understanding key terms like CISC, super scalar, out of order, Von Neumann architecture, and speculative execution is crucial for comprehending further arguments.
  • Von Neumann's significant contributions to computer science, including the Von Neumann architecture, are highlighted, with references to the book "The Three-Body Problem."
  • The Von Neumann architecture allows both program and data to exist in the same memory space, eliminating the distinction between program and data memory.
  • Super scalar CPU cores can execute multiple instructions per clock cycle, leading to higher performance than the clock speed might suggest.
  • Modern x86 CPUs can execute instructions out of order, optimizing performance by rearranging instructions for efficiency.
  • Pipelining in CPUs involves overlapping stages of instruction execution to maximize clock speed and overall performance, allowing for multiple instructions to be processed simultaneously.

26:10

"Pipelining in CPUs: Efficiency and Speed"

  • Ads move through a pipeline, with one ad put in and one ad out every clock cycle.
  • The process makes it seem like only one cycle is needed to complete an ad, despite multiple cycles being involved.
  • An analogy of a washer and dryer is used to explain the concept of pipelining.
  • Pipelining involves breaking work into smaller chunks to increase efficiency.
  • Out of order execution allows for tasks to be completed in any order if they are independent.
  • Superscalar execution involves executing multiple tasks simultaneously if possible.
  • Speculative execution involves running instructions before confirming their necessity, posing security risks.
  • The M2 bug is distinct from Spectre and Meltdown, involving the memory prefetcher.
  • The Zen 4 CPU supports real mode and 8086 instructions, performing multiple operations per clock cycle.
  • Zen 4 is significantly faster than the 8086 due to its capabilities and support for older instructions.

39:05

Understanding Micro Ops in 16-bit CPUs

  • CPUs operate on 16 bits
  • Micro Ops are crucial for understanding computer operations
  • Micro Ops are used for instructions like "add"
  • Different ports on CPUs handle different operations
  • CPUs can execute up to four ads per cycle
  • Micro Ops wait in a scheduler for execution resources
  • Queue management is complex and dependent on dependencies
  • More ports on an instruction mean more operations, not more bits
  • x86 supports various memory operands for instructions
  • Instructions like "mpsa DBW" have specific functions and costs

52:31

"Evolution of CPU Architectures: x86 vs ARM"

  • CPUs run instructions out of order, like modern x86, to optimize performance.
  • Register renaming allows multiple instructions to run simultaneously without conflicts.
  • Decoding complexity in x86 and x64 architectures poses challenges for efficient execution.
  • ARM and RISC-V instruction sets are gaining popularity over x86 due to simplicity and efficiency.
  • ARM dominates smartphones and single-board computers, while RISC-V is widely adopted in microcontrollers.
  • RISC-V's royalty-free nature makes it popular in computer science classes and various platforms.
  • The evolution of x86 over 46 years has led to complex execution methods like super scalar and speculative execution.
  • Decoding logic complexity in x86 and x64 architectures impacts efficiency and performance.
  • Improving decoding logic in x86 could enhance efficiency and reduce the strain on CPUs.
  • The days of x86 dominance may be numbered as ARM and RISC-V gain traction in various markets.

01:06:06

Simplifying Instructions for Efficient Time Allocation

  • Engineers are spending time decoding instructions, highlighting the need for simpler processes to allocate time efficiently.
  • Despite a serious problem existing, the framing and approach to addressing it often miss the mark, with a low success rate in articles and discussions.
  • The conversation touches on CPUs and potential future collaborations, with a mention of a paid computer-enhanced content platform and the possibility of creating an 8-bit computer tutorial.
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