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Despite Aging Design, x86 Still in Charge
An anonymous reader writes "The x86 chip architecture is still kicking, almost 30 years after it was first introduced. A News.com article looks into the reasons why we're not likely to see it phased out any time soon, and the history of a well-known instruction set architecture. 'Every time [there is a dramatic new requirement or change in the marketplace], whether it's the invention of the browser or low-cost network computers that were supposed to make PCs go away, the engineers behind x86 find a way to make it adapt to the situation. Is that a problem? Critics say x86 is saddled with the burden of supporting outdated features and software, and that improvements in energy efficiency and software development have been sacrificed to its legacy. And a comedian would say it all depends on what you think about disco.'"
It should be replaced with Esperanto when we all upgrade to Vista.
technical writing / development
I'm going to go with:
Did I miss anything?
If you disagree, post your argument. (-1, Overrated) isn't your personal censorship tool for views you don't like.
The x86 instruction set will be retired in the same year as the QWERTY keyboard layout.
Just like the four stroke engine. It's not the best one, it can be largely enhanced and made better, but it's still here.
And just like the four stroke engine, modern engines just burn gasoline and push car forward. This is where the similarity with the original engines end.
Maybe Computers will never be as intelligent as Humans.
For sure they won't ever become so stupid. [VR-1988]
At this point, does it matter as much? As we move on the future is clearly x86-64 which is MASSIVELY cleaned up compared to x86 and is really rather clean compared to that. Sure at this point we still boot into 8086 mode and have to switch up to x86-64 but that's not that important, it only lasts a short while.
As we move off of x86 onto -64, are things really still that bad? Memory isn't segmented, you have like 32 different registers, you don't have operands tied to registers (all add instructions must use AX or something like that) as some 16/32 bit instructions were.
Of course, we should have used a nice clean architecture like 68k from the start, but that wasn't what was in the first IBM.... and we all know how things went from there.
Comment forecast: Bits of genius surrounded by a sea of mediocrity.
Yes, the instruction set is old, but, it does still work. As a consumer, why should I have to re-invest in software that I purchased and does the job, just becuase my hardware failed, or faster hardware becomes available and I upgrade. Apple bit that one some time ago. Last year, I had an investment of $4000.00 in software when Intel came out with a significantly faster part that was dropping in price. Just by upgrading my hardware (cost $800) my invenstment improved significantly. $4800.00 did not justify the upgrade but the low cost of hardware only, did. Also, there was not learning curve involved.
You don't buy a new car just becuase the tires need replaceing (well some people do, but that is rarely the fiscally responsible thing).
If it ain't broke, it doesn't need fixing.
Athiesm is a religion like not collecting stamps is a hobby.
Things would be a lot easier if the darned thing wasn't so bloody complex to emulate. I mean if we were "stuck" with (say) an ARM or even a 68K we'd be able to use virtual machines to dig ourselves out of a similar architectural hole (though with an ARM we'd be unlikely to want to).
:-)
The x86 has so many modes of operation (SMM, real/protected, lots of choices for vectorizing instructions, 16/32/64 bit modes) and special cases that it's a pretty big project to get emulation working correctly (much less fast). You're pretty much stuck with a 10x reduction clock-for-clock on a host. Making an emulated environment secure is hard, too; you don't necessarily need specialized hardware here (e.g., specialized MMU mapping modes), but it helps.
And now, with transistor speeds bottoming-out, they want to go multicore and make *more* of the things, which is exactly the opposite direction that I want to go in...
Any sufficiently advanced technology is insufficiently documented.
Who is this guy and what is he smoking? Over half of a modern processor is cache. The instruction decoding and address decoding are a small fraction of the remainder. Where does he get the 60% from?
Sometimes I doubt your committment to SparkleMotion!
I know we all bitch about old designs, legacy support for outdated features, but, one of the things that keep people from moving from one OS to another is "existing base of installed software" and "knowledge of exisiting software". Like it or not, the major player is Microsoft. No matter how much a geek says, MS UI's suck, people are comfy with them. If alternative OS's had the same software offerings with the same UI, people would be able to move to them. The same holds true for processors.
No matter how well a processor performs, if there is no application base for it, no one is going to buy a machine with that processor. In this case, perception is reality. You walk into a software store, you see 16 rows of Windows applications, half a row of Linux, and 5 rows of Apple.
What processor family runs each of these? Guess who has moved to the dominant processor?
The only way to build a software base is to build in legacy support. Then start weening users away from the legacy features, get programmers to stop using those features (mainly those building the compilers that developers use), and move towards the more advanced features.
x86 rules for a reason. Microsoft rules for a reason. The customer is comfortable with them, and their perception is reinforced everytime they go to the store.
Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong fix.
4. Price / performance. A segment the x86 have done well in.
:D
5. Security. Will my x86 progs be supported in 20 years? The answer: yes.
6. Availability. Hmm... Intel, I'd like to 1 000 000 CPUs. Intel: Sure thing.
7. Good will. What should we buy, Intel or PPC. PPC? What's that? Go Intel! Yes boss. (Just look how far Itanium got on Intel's name, alone.)
Already been done, didn't catch on (see Itanium).
Because there is such a massive amount of installed x86 software base that you'd be throwing away silicon. To be sure that software ran on the most systems possible, software would still be written for x86 and not the 'desired' architecture.
That being said, OSS tends to have good inroads in that you get all the source so can recompile to whatever architecture you want. However, since x86 is still the huge marketshare, other architectures get less attention. Also, all of the JIT languages (Java, C#, etc.) make transitioning easier IF you can get the frameworks ported to a stable environment on the 'desired' architecture.
The main problem is that there is *so* much legacy code in binary (EXE) format only (the source code for many of those has been literally lost) that can be directly tracked to money. There are systems that companies continue to use and have so much momentum that changing platforms would require extreme amounts of money to reverse engineer the current system - complete with quirks and oddities, rewrite, and (here is a big part that many people fail to add in) retest and revalidate, that many companies don't want to spend that kind of money to replace something that 'works'.
There's so much work/time/effort invested in x86 now that it's hard to jump off that train. AMD's x86-64 is a good approach in that you can run all the old stuff and develop on the new at the same time with few performance penalties. However, I don't know if we'll ever be able to shrug off the burden of x86.... at least not for a long time to come. It'd take something truly disruptive to divert from it (and what people are currently invisioning as quantum computing is not that disruption).
Boot loaders tend to be 16bit segment model code 8086, at least they contain enough code to get into 32bit mode. The BIOS will be 16bit legacy code, at least some anyway as a x86 PC chip still boots in Real Mode (there is a 386 embedded variant that doesn't). Windows 9x series is _RIDDLED_ with 16 bit code esp the display drivers, although many of these switch to 32bit mode ASAP the entry points are 16 bit code. Any attempt at killing off 16bit code would stop any 9X system running.
For WinNT and variants (2K, XP) I don't know how much 16bit code is in there. I've written drivers for 2K/XP and could not find a single 16bit style instruction however even NT series for x86 uses segments. FS is used for process & thread info. IIRC even AMD64 long mode implements FS & GS to make OS porting easier.
Lastly. 16bit code (instruction operating on 16bits of a 32bit register) are trivial in 32bit mode - all you have to do is preceed an instruction with 0x66 and/or 0x67 to switch a 32bit instruction to a 16bit instruction.
The problem transcends MSDOS and goes to the BIOS and boot sequence itself. Intel tried to address the with EFI but that seems to be slow gaining traction - probably because of backwards compatibility.
Time flies like an arrow. Fruit flies like a banana.
Computer manufacturers have tried making non-compatible machines. Commodore 64, VIC 20, Coleco Adam, Atari ST. They all had their place in time and their niche in the market before fading out.
Something they all had in common, though, is that they sold better than IBM's mostly-compatible PCjr. I attribute that difference to software and compatibility problems. Because of BIOS differences, a number of programs written for the PC couldn't run on the PCjr. That led to a fragmentation of shelf space at software retailers and confusion among retail customers, and led to customers avoiding the platform in favor of easier-to-understand options.
I would expect something similar to happen if Intel, AMD, or anyone else started making mostly-compatible x86 processors. It wouldn't sell unless all of the software people are used to running still worked. Sure, someone could take Transmeta's approach and emulate little-used functionality in firmware rather than continuing to implement everything in silicon, but it all pretty much needs to keep working, so why bother?
Seriously, why would anyone undertake the effort and expense needed to slim-down x86 processors when the potential gains are small and the market risk is pretty huge? No chip manufacturer wants to replace the math-challenged Pentium as the most recent mass-market processor to demonstrably not work right.
Pundits and nerds can talk all they want about why the x86 architecture should be put out to pasture, but it won't happen until a successor is available that can run Windows, OSX, and virtually all current software titles at acceptable speeds. At that seems pretty unlikely to happen on anything other than yet another generation of x86 chips.
You know, there is a difference between trolling and pointing out the flaws in your reasoning. Just saying.
Actually the encoding is VERY efficient where it matters most, cache density and limiting the number of calls to main memory. Having complex instructions helps in the areas where real world performance is most hurt and that is why we have a CISC frontend to an efficient RISC backend. This balance was reached even in the "RISC" camp, look at the PPC970 with the more complex instructions that get broken down in uops and dispatched to execution units, very similar in many ways to how modern x86 processors work. The translation layer is less than one percent of die space and probably a much lower percent of power usage on modern x86 chips.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
The irony of being a grammar Nazi by pointing out that the statement "People like you make Nazi's look good." is incorrect. It should be "People like you make Nazis look good." - unless there is some unseen object that the Nazis posses, the apostrophe before the "s" is unnecessary and incorrect. Simply adding a "s" to the end is sufficient to make it plural.
"But this one goes to 11!"
...rather than intelligent design.
"How to Do Nothing," kids activities, back in print!
> Now, this is the important part: He's used to XP. He's used to an OS, that while sucky, worked well enough for him, was relatively speedy, so why can't he just have that? Why does he have to have something replaced that worked just to put up with this shit?
If instead of giving up after a day, he had tried it for a week or a month, he would have found out how great everything is. Then in a few months he would be used to it and if you try to make him downgrade to XP he will cry.
There are many great features in Vista, but you have to try it for yourself.
I'll probably be modded down for this...
Any processor has to do the exact same work, whether the user-visible encoding is done this way or as an "SP indexed" addressing mode. At the micro-op level, it all gets renamed, reordered, etc. so that the same things are happening. Moreover, that particular sequence is so common, in all probability most X86 CPUs have special logic just to optimally execute that entire sequence faster that the naive RISC equivalent.
What's with all this dissing of the X86?
Like you, I'm an old fart; I wrote assembler code for the PDP-8, PDP/LSI-11 and the 68k. They were ok: easy to learn and use, but I always preferred the X86.
Sure, it was harder to learn and I never got past having the blue book on my desk when I was coding but, in the end, it produced smaller, faster code. There were a number of apps I wrote for multiple platforms, so I got to compare. Also, (the same reason I love perl) you could do astounding things with side-effects.
Commercially, X86 has staying power because it was architected to scale. Variable-length instructions with lots of space in the operator range lets Intel adapt the design to any new demands. Most, if not all, of the complaints about X86 (e.g. too few registers) are just version features—yesterday's news if there's a market demand for an improvement.
Bottom line—it ain't neat, but that doesn't matter; it's programmed once and used millions of times. Programmer convenience is irrelevant.
I'm a Programmer. That's one level above Software Engineer and one level below Engineer.
I tried looking into my heart but it asked me to "allow" or "deny". When I hit "allow" I got a BSOD. I'll have to get back to you on that one.
The x86 instruction set is a surprisingly good way to build a computer. The reasons aren't obvious.
First, the original x86 was a huge pain, with that stupid segmented memory arrangement. But IA-32 was better and cleaner; at last there was a flat 32-bit address space. (Yes, there's a segmented 48-bit mode, and Linux even supports it, but at least apps see a flat address space.) AMD-64 is even more regular; the segmented memory stuff is completely gone in 64 bit mode. So there is progress.
RISC architectures could yield simple machines that could execute one simple fixed-width instruction per clock cycle. The early DEC Alphas, the MIPS machines, and early IBM Power chips are examples of straightforward RISC machines. This looked like a big win. The ALU was simple, design teams were small (one midrange MIPS CPU was designed by about six people), and debugging wasn't hard. RISC looked like the future around 1990.
What really changed everything was advanced superscalar architecture. The Pentium Pro, which could execute significantly more than one instruction per clock, changed everything. The complexity was appallingly high, far beyond that of supercomputers. The design teams required were huge; Intel peaked somewhere around 3000 people on that project. But it worked. All the clever stuff, like the "retirement unit" actually worked. Even the horrible cases, like code that stored into instructions just ahead of execution, worked. It was possible to beat the RISC machines without changing the software.
The Pentium Pro was a bit ahead of the available fab technology. It required a multi-chip module, and was expensive to make. But soon fab caught up with architecture, and the result was the Pentium II and III, which delivered this technology to the masses. Then AMD figured out how to do superscalar x86, too, using different approaches than Intel had taken.
The RISC CPUs went superscalar too. But they lost simplicity when they did. One of the big RISC ideas was to have many, many programmer-visible registers and do as much as possible register-to-register. But superscalar technology used register renaming, where the CPU has more internal registers than the programmer sees. The effect is that references to locations near the top of the stack are as efficient as register references. Once the CPU has that capability, all those programmer-visible registers don't help performance.
Making all the instructions the same size, as in most RISC machines, leads to code bloat. Look at RISC code in hex, and you'll see that the middle third of most instructions is zero. Not only does this eat up RAM, it eats up memory and cache bandwidth, which is today's scarce resource. Fixed size instructions simplify instruction decode, but that doesn't really affect performance all that much. So x86, which is a rather compact code representation, actually turns out to be useful.