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Introduction to 64-bit Computing and x86-64

James writes "Ars Technica has an article up explaining 64-bit computing from the x86 angle, specifically from the angle of AMD's Hammer. The article explains the details in that usual Ars style, and I found it very useful for thinking about what kinds of applications I may want to put to the test on one of these when we get a box in the office. Even non-x86 freaks may appreciate this, since it breaks down some of the basic advantages of 64-bit computing, and just who can expect to see gains in the near future."

9 of 259 comments (clear)

  1. Re:Mix code in long mode? by CoolVibe · · Score: 4, Insightful

    Well, the industry can always revert to what Apple did if it isn't possible. Make "Fat" executables. ia-64, ia-32 and x86-64 in one executable. Sure, the binaries will be bigger, but with harddisk prices nowadays I don't believe disk space is really an issue :)

  2. intel hack by avandesande · · Score: 3, Insightful

    Furthermore, Intel supposedly has a fairly simple hack that they could implement to allow their 32-bit systems to address up to 512GB of memory. Still, the cleanest and most future-proof way to address the 4GB ceiling is a larger pointer
    They forget to mention that even if you can have more than 4gb on xeon machine you cannot address any single block of more than 4gb. Forget about putting your oracle db into memory.

    --
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  3. Why NOT? by gspr · · Score: 3, Insightful

    "Why not do it?" is usually a bad question, but in this particular case, I think it's a good one. If there is no performance penalty when running in Legacy Mode, and if the Hammer is going to be cheap (read: reasonably priced compared to the P4), why NOT buy it?
    It doesn't hurt, and it prepares you for the future, a future that will come, now or later. This way there'll at least be a chicken... then we can just wait for the eggs to appear. It's foolish to think that any eggs will appear before the chickens do. Afterall, the only place you can get a chicken from before there are eggs, is from AMD's chicken replication facility.

  4. Will Microsoft survive the 64-Bit transition? by RoLi · · Score: 5, Insightful
    The 64-Bit transition comes with a lot things, all bad for Microsoft:

    • For the first time in computing history AMD and Intel no longer see Microsoft as the sole software provider. Both Intel and AMD support Linux from day 1 on their 64-chips. I repeat: That did not happen before. So far, Linux was never available on a chip's introduction.
    • On Operon and Itanium, Linux is available before Windows.
    • In the first 1 or 2 years, 64-chips will be mainly used on servers, where Linux is already strong.
    • To use the additional features/registers, a recompile is neccessary - OSS will use those features right away, while CSS vendors will take quite some time to release a 64-Bit version and will probably want some money for the upgrade.
    • The traditional Windows-on-servers customer is a very conservative market segment not likely to jump on the 64-Bit bandwagon very early.

    To summarize, Microsoft might run into a chicken-and-egg problem on 64-Bits: Nobody runs Windows on 64-Bits because it's not faster -> Nobody makes Win64 software -> Nobody runs Windows on 64-Bits.

    Add into that the fact that Microsoft is traditionally very incompetent and slow when it comes to adopting new architectures and you get the idea.

    I think that Microsoft will lose the majority of their server marketshare and a large chunk of their desktop marketshare during that transition. Simple market inertia will prevent Microsoft to be thrown out of the desktop market, but because of the 64-Bit transition, the Linux desktop market might finally gain critical mass and endanger the Windows domination in the long term.

    1. Re:Will Microsoft survive the 64-Bit transition? by RoLi · · Score: 4, Insightful
      After all, Microsoft HAS developed a version of Windows XP Professional that works on the Itanium CPU in IA-64 mode, for gosh sakes!

      Well, although I have never seen a review about that, never seen a Wintel64 system on sale and don't know what dirty hacks and workarounds are in the package, let's assume that's true.

      Now look at my post again: All the points I made are still valid, the most important one being that Linux is being supported right from the start for the first time.

      I'm sure that Microsoft is right now working a version of Windows XP Home/Professional that works on the AMD Athlon64/Opteron CPU's in x86-64 native mode

      While I'm also sure that they are working on it, I'm not about their ability to ship a working product on time. On the other side, SuSE has already successfully ported Linux to mainframes for IBM (something I don't think MS could do with Windows in a timely manner) and they are now porting Linux to Opteron - or better have already ported it as Beta-systems are already out there. - Where is the Windows-Operon Beta? I don's see it.

      In case you forgot, Microsoft was YEARS late in finally adequately supporting 32-Bit (actually, Intel was already quite angry at MS that their chips were still used in 16-Bit mode almost exclusively for so long). Of course by that time, there was no alternative, so Microsoft got away with their incompetence, but now there is not only an alternative, it is also supported officially by AMD and Intel.

  5. 64-Bit: The "Torque" of a Processor? by Spencerian · · Score: 4, Insightful

    I'm not an engineer.

    What I got from this article (well written, BTW) is that 64-bit processors provide more processing power--a concept different from speed. For instance, a Porsche can fly down the highway, but its engine has insufficent power to tow a 5th wheel RV. A Mack truck isn't speedy, but has a strong engine that can tow the heaviest loads up the same speed--more work is performed.

    That would be why Apple's PowerPCs are still in the running, despite their clock slowness. They are falling behind fast as, after a point, speed does matter, in combination with improved processor power in the latest 32-bit Pentiums, and certainly the Xeon. Vector processing, such as Altivec, helps keep Apple competitive with their current chips--just barely. Many in the PC community await AMD's offering while IBM works on blending its POWER chip technology into a 64-bit PowerPC, with Altivec.

    Imagine making the Porsche's engine more powerful but maintaining its speed advantage so it can haul ass as well as tow. Add nitro for extra ooompf (vector processing) and you have a dream machine. That's why it seems that 64-bit apps and processors seem to be such a holy grail.

    That's my take on it. Clarification is always appreciated.

    --
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  6. PPC by Duncan3 · · Score: 5, Insightful

    "Should Apple move from 32-bit PPC to 64-bit PPC, Mac users should not expect the same kinds of performance gains that x86 software sees from the jump to x86-64. 64-bit PPC gives you larger integers and more memory, and that's about it. There are no extra registers, no cleaned up addressing scheme, etc."

    Well yea, they already have more then 0 general purpose registers, and a flat memory space, like every other chip besides x86 has had for the last 20 years now. The embedded chips I've used on projects that cost $7 a piece even have more registers then x86 does.

    64bit is about the memory, and using that memory, plain and simple. x86 just happens to be using this as a chance to catch up with the cutting edge concepts of the 1980s.

    As for x86 needs to die once and for all, it's hacked, hacked again, and hacked yet again. x86 was and is a 16bit system. And now AMD wants to hack it yet again. Can anyone doubt that 80% of the silicon is for supporting legacy apps at this point? Are people that damn lazy they can't type 'make' on a new system? It's not like anyone uses "int" anymore and assumes it's N bits long.

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    1. Re:PPC by pjl5602 · · Score: 3, Insightful
      As for x86 needs to die once and for all, it's hacked, hacked again, and hacked yet again. x86 was and is a 16bit system. And now AMD wants to hack it yet again. Can anyone doubt that 80% of the silicon is for supporting legacy apps at this point? Are people that damn lazy they can't type 'make' on a new system? It's not like anyone uses "int" anymore and assumes it's N bits long.

      Legacy X86 is dying. But really, how much die space does the 386 real mode take up? A few hundred thousand transistors? That's nothing these days so it's worth keeping it around even if only 0.001% of your customers make use of it simply from a marketing perspective.

      Then, from the article:
      When AMD's engineers started looking for legacy x86 features to jettison, the first thing to go was the segmented memory model. Programs written to the x86-64 ISA will use a flat, 64-bit virtual address space. Furthermore, legacy x86 applications running in long mode's compatibility sub-mode must run in protected mode. Support for real mode and virtual-8086 mode are absent in long mode and available only in legacy mode. This isn't too much of a hassle, though, since, except for a few fairly old legacy applications, modern x86 apps use protected mode.

      So the X86-64 mode will be fairly cruft free.

      Pat

  7. TCPA (was Re:64 bit chips R cool . . . by ultrabot · · Score: 3, Insightful

    but I'll be buying them if and only if they don't include TCPA/Palladium/Trusted PC Platform/Name of lockdown scheme of the week.

    I dunno, TCPA seems kinda cool & useful. It doesn't lock down anything, it is basically just a way to encrypt/decrypt data without having the keys on a local file system (i.e. keys are stored on a black-box hardware). Spreading popularity of TCPA might also render Palladium and other DRM methods worthless. TCPA != DRM. Some IBM articles reported on /. a while ago clarified this point quite a bit.

    With TCPA, *you* would hold all the keys (since you can access your own hardware, hopefully), and no centralized entity (*cough* ms *cough*) would have anything to say about it.

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