what 64bit?

What exactly does 64bit mean?

I've been told that Windows won't be able to get a true 64bit system for years, because of compilation issues etc. Is this true? What does it all mean? How many people are asking the same question? Does anyone care?

i think 64 bit refers to the size of words that a computer works with, and the size of the registers as well. do you remember in CS class when they said the size of an integer is usually 4 bytes, but it varies by system? Well most systems are 32 bit, so with 8 bytes a bit that makes sense, yes? I believe that Sun Workstations are one of the few that are 64 bit right now, so i would assume that the size of integers on them is 8 bytes. but i tihnk your best answer would come from google...

Here is a decent article from MS that explains technically what
it means to be 64-bit
http://www.microsoft.com/windowsxp/...luation/faq.asp

From the above MS link:

Q.
Will Windows XP 64-Bit Edition be available in retail stores?
A.
No, Windows XP 64-Bit Edition will be available only through OEMs that offer Itanium-based hardware and available via the Microsoft Developers Network (MSDN).

Does this mean that regular Windows machines won't get 64-Bit? Will this put Apple at a speed advantage?

64-Bit software/OS requires a 64-bit processor. That is what the Itanium is. All other Intel processors are 32-Bit.

A current windows machine will not get 64-Bit, but newer workstations will, depending on what kind of processor it has in it.

According to Apple, they are already at a speed advantage. But that is just according to Apple, I couldn't prove this either way.

This means that you can't but the 64-bit version through retail.
you can only get it bundled with a PC. This won't last though...

64 bit does offer some great speed enhancements, the only problem is applications will have to be rewritten.

The Itanium is only 64bit, which means everything that runs on it must be written for a 64bit processor. The new AMD chip is compatible with both 32 and 64 bit.

The fact that applications need to be rewritten will be the biggest obstacle to getting 64 bit.

Honestly, most applications don't need 64-Bit. It is overkill. It is like getting a 3GHz machine just to read email. Most applications that we currently have do not have a need for this yet. This may change in the future, but as of yet it is still overkill.

I'd like to point out that different 64-bit chips are incompatible with each other. The AMD Opteron and the Intel Itanium are both 64-bit chips, but can't run each other's software. The same goes for Sun's Sparc, DEC's Alpha, and Motorolla's PowerPC.

And 64-bit isn't necessarily faster. If the application can utilize the extra memory, it will be. If the application can take advantage of the extra native percision, it will be. But that's about it. Yes, newer processors will have newer and faster implimentations, and 64 bit chips have often had shorter pipelines meaning more useful work done per clock cycle.

However, with the 64-bit memory addressing, lots of lookups will require twice the memory bandwidth of current 32-bit lookups. Same goes for doing integer calculations. If doing math to small data types (where 32-bits is most often more than enough), there's a huge excess of wasted register space (unless you've programmed it to perform in parallel ala SIMD instructions).

So don't let the numbers fool you, 64-bit is a major step, but one that will take some time to realize even a fraction of its potential.

All that said, I'm going to look up a big technical article on Itanium. Its architecture is very interresting.

I have the architecture books for it.

All the effort in other systems put into predicting branches, trying to decide how much of the current code can be executing in concurrent pipelines, all gone. The chip has several execution units (not to mention the possibility of multiple CPUs) and all parallel operations are predetermined at compile time, not run time. There's several orders of magnitude more time to make that decision when compiling than when executing. Makes writing a compiler a trip and half, but the execution time benefits could be remarkable. And when it comes time for branch prediction, screw it, execution both of them, discard the one not taken. No penalty.

Forget the article, that's about all I wanted to say. Of all the platforms I've studied, that's by far the most interresting. Well, that and why in god's name are we still using x86.

When Microsoft launched Windows95(32Bit) after Windows3.1(16Bit) there weren't any real complication about rewritting applications, so why would 32->64 bit be different?

64 bit processers are mainly a memory upgrade from the 32-bit. 64 will also allow larger bus upgrades which will also sadly cause more clutter and margin for error ..between windows crashing and the new arch. something new has to be worked out to maintain a stable system.

Not being much of a hardware guy, I have to wonder (this probably ties in with what Onslaught said about sandblasting soupcrackers when reading email)... with the current x86 setup, the processor is by far the most underutilized peice of the system. For example, jumping from my current 866MHz P3 to the top of the heap: a 1.2 GHz P3 chip, would do almost nothing for the performance of my system, and certainly not enough to justify the 120.00 expense. The bottleneck on the memory (which is in turn limited by the dated chipset on the mobo) and the hard disk simply makes my CPU upgrade a feel good change.

That said, would moving from a 32 bit to a 64 bit arch be worthwhile, or would the whole system as we know it need to be redesigned? Obviously buses would need to be widened, but what about other bottlenecks like the previously mentioned RAM limits and other components - disk access is still slow as all get out.... would it be worth it?

In response to cubo's question: I believe that at the time that move took place, most systems were running 80486 and Pentium chips which are both 32 bit archs. I imagine that you probably can't run Win95 (even poorly) on an 80386 or 80286 because they are 16 bit.

I think it's not so much that apps., will have to be re-written, rather, I think apps., will have to be modified slightly, re-linked/compiled to run on 64-bit chips. Someone out there is going to make a lot of money porting software and writing IA64 compilers!

I think the Itanium, Opteron etc., will go the way of SMP - utilized almost exclusively on server platforms. Oh, that and renderfarms!


nao