SoylentNews

Ask SN: When Is Assembly Worth It?

posted by Cactus on Saturday March 08 2014, @07:30AM   
from the don't-tell-me-upgrade-PCs dept.

Subsentient writes:

"I'm a C programmer and Linux enthusiast. For some time, I've had it on my agenda to build the new version of my i586/Pentium 1 compatible distro, since I have a lot of machines that aren't i686 that are still pretty useful.

Let me tell you, since I started working on this, I've been in hell these last few days! The Pentium Pro was the first chip to support CMOV (Conditional move), and although that was many years ago, lots of chips were still manufactured that didn't support this (or had it broken), including many semi-modern VIA chips, and the old AMD K6.

Just about every package that has to deal with multimedia has lots of inline assembler, and most of it contains CMOV. Most packages let you disable it, either with a switch like ./configure --disable-asm or by tricking it into thinking your chip doesn't support it, but some of them (like MPlayer, libvpx/vp9) do NOT. This means, that although my machines are otherwise full blown, good, honest x86-32 chips, I cannot use that software at all, because it always builds in bad instructions, thanks to these huge amounts of inline assembly!

Of course, then there's the fact that these packages, that could otherwise possibly build and work on all types of chips, are now limited to what's usually the ARM/PPC/x86 triumvirate (sorry, no SPARC Linux!), and the small issue that inline assembly is not actually supported by the C standard.

Is assembly worth it for the handicaps and trouble that it brings? Personally I am a language lawyer/standard Nazi, so inline ASM doesn't sit well with me for additional reasons."

• Re:you're a precious one, aren't you Re:you're a precious one, aren't you (Score: 5, Funny) by M. Baranczak on Saturday March 08 2014, @03:37PM

  by M. Baranczak (1673) on Saturday March 08 2014, @03:37PM (#13212)

  Seriously, how many people feel the burning desire to run multi-media apps under Linux on a Pentium 1? Three, four? Why don't you just call these people on the phone and summarize the plot of the movie for them?

  Parent

  Starting Score:	1		point
  Moderation		+4
  Funny=4, Total=4
  Extra 'Funny' Modifier		0
  Total Score:		5

• Re:you're a precious one, aren't you (Score: 2) by maxwell demon on Saturday March 08 2014, @06:22PM

  by maxwell demon (1608) on Saturday March 08 2014, @06:22PM (#13255) Journal

  Because the movie industry would sue him for copyright infringment. Duh.

  --
  The Tao of math: The numbers you can count are not the real numbers.

  Parent

• Re:you're a precious one, aren't you Re:you're a precious one, aren't you (Score: 0) by Anonymous Coward on Sunday March 09 2014, @07:18AM

  by Anonymous Coward on Sunday March 09 2014, @07:18AM (#13478)

  Regard the Pentium 1 / Pentium Pro dividing line, even if folks dodge the CMOV issue, there is another gotcha: Distros are starting to require support for PAE [wikipedia.org].

  I can't even count the number of times I've seen folks in forums say "I have a Pentium M" without specifying Banias or Dothan [wikipedia.org]. (Banias does not support PAE.)

  -- gewg_

  Parent

  • Re:you're a precious one, aren't you (Score: 0) by Anonymous Coward on Monday March 10 2014, @09:14AM

    by Anonymous Coward on Monday March 10 2014, @09:14AM (#13797)

    Banias or Dothan

    And my axe!

    Parent