3 ms·

If you go further down, at least on x86 you'll find a lot of duct tape. I guess most people who have written serious code in x86 assembly wonder how those machi

by phaer 13y ago

If you go further down, at least on x86 you'll find a lot of duct tape. I guess most people who have written serious code in x86 assembly wonder how those machines can actually work so reliable in practice. Probably because kernel developers do a good job. // my perspective: I started with low level c and assembly, mainly on x86 and do web programming nowadays.

Scramblejams 13y ago
I don't doubt it, I've avoided x86 because it has that reputation. My time was spent on 8051 and MIPS.
pbsd 13y ago
What do you mean by duct tape on x86? I'm quite familiar with the architecture, and this can be interpreted in more than one way.
- na85 13y ago
  Well for one thing, the machines need to maintain 8086 compatibility even though it is horribly outdated. IIRC the actual processor just runs microcode that emulates an x86-compatible system or something to that effect. It's sort of like gcc where layers keep getting put on top of layers and only like 5 wizards from MIT know how it actually works.
  - tptacek 13y ago
    The word "emulation" is uncharitable. Breaking a high-level instruction into micro-operations allows the architecture to present a consistent ISA to programmers while optimizing execution for the micro-architecture. Yes, x86 originally did this out of necessity. But it's a little unfair to call it "duct tape". Case in point: ARM sometimes does the same thing, despite being a RISC. In other words: design your clean, orthogonal RISC ISA however you want: at some point in the future, some processor designer is going to end up translating those instructions into something else. As for layers upon layers of abstractions: welcome to computer science. ;)
- VLM 13y ago
  "this can be interpreted in more than one way." One flavor can be seen in the A20 gate http://en.wikipedia.org/wiki/A20_line http://en.wikipedia.org/wiki/A20_line 30 years after it was inserted into the architecture to work around some software issues/bugs, bootloaders still have to fool around with it every time a x86 machine is booted. Lovely.

by phaer 13y ago

Scramblejams 13y ago

I don't doubt it, I've avoided x86 because it has that reputation. My time was spent on 8051 and MIPS.

pbsd 13y ago

What do you mean by duct tape on x86? I'm quite familiar with the architecture, and this can be interpreted in more than one way.

na85 13y ago
Well for one thing, the machines need to maintain 8086 compatibility even though it is horribly outdated. IIRC the actual processor just runs microcode that emulates an x86-compatible system or something to that effect. It's sort of like gcc where layers keep getting put on top of layers and only like 5 wizards from MIT know how it actually works.
- tptacek 13y ago
  The word "emulation" is uncharitable. Breaking a high-level instruction into micro-operations allows the architecture to present a consistent ISA to programmers while optimizing execution for the micro-architecture. Yes, x86 originally did this out of necessity. But it's a little unfair to call it "duct tape". Case in point: ARM sometimes does the same thing, despite being a RISC. In other words: design your clean, orthogonal RISC ISA however you want: at some point in the future, some processor designer is going to end up translating those instructions into something else. As for layers upon layers of abstractions: welcome to computer science. ;)
VLM 13y ago
"this can be interpreted in more than one way." One flavor can be seen in the A20 gate http://en.wikipedia.org/wiki/A20_line http://en.wikipedia.org/wiki/A20_line 30 years after it was inserted into the architecture to work around some software issues/bugs, bootloaders still have to fool around with it every time a x86 machine is booted. Lovely.