Originally posted by: RedComet87
I?ve been researching computer parts for the past couple of days and I had to make a very tough decision. A 32-bit Intel 3.4ghz or a AMD 64-bit CPU. After reading tons of articles and forums all over google I came to the conclusion that nobody seems to know what?s going to happen with this tech. It seems to me that all the reviews and critiques of the 64bit CPU say, "It could revolutionize." I read one review that simply stated that 64-bits are wasted on desktop computers. They said servers are the only ones that need the number crunching power and bandwidth that 64bits offer.
When I get on forums, everyone is always suggesting the AMD CPU, saying, "Its the next generation," and "computers everywhere will have it soon."
I can see the uses for computers that run advanced modeling and artwork apps, like a mac, but is it needed for regular apps and games?
Right now I am sided with Intel, it makes sense to me that 64bits are only good for servers. Tell me if I?m wrong, but I think that 32bits are enough to accomplish any desktop computer's objective. That, with the new PCI-Express tech, and I built myself a pretty good looking computer.
http://secure.newegg.com/app/WishR.asp?ID=1057241 (feel free to critique via pm please, I can always use suggestions )
So I must ask, are the AMD 64-bit cpus over hyped? Do desktop computers really need to have a built in calculator to rival their video cards? It seems to me that using a 64bit processor would be like sending data down the Mississippi on a surfboard. It has so much potential to do work that no desktop computer can satisfy it.
Well, we really need a 64-bit OS and 64-bit apps to make use of 64-bit. But it's forthcoming.
64-bit is primarily about linear virtual address space, secondly about virtual address space, thirdly about addressable ram.
We are approaching the limits of what can be done with our current, linear 32-bit memorymodel, software.
Some applications have a hard time even today (for some users) and future applications cannot exist on current 32-bit. They have to migrate to some other software format. One option is the one Oracle have taken, segmented 32-bit memory model. Words are not enough to express how ugly this is. basically it's a return to old Windows 16 technology. Noone wants that. Intel may briefly have wanted it, just to harvest all those customers fleeing from it, with their Itanium, but I don't think they do anymore.
In my estimate, 64-bit software compatibility might be more useful than PCI-E. I don't quite see any great need for that.
I'll repost my 64-bit FAQ. See if you're helped by that.
****************
Q: Why would we need a 64-bit processor?
A:
In order to be able to run 64-bit software.
Q: Why would we need to run 64-bit software?
A:
Because 32-bit applications and OSes are at the end of the line. They basically can't evolve much farther, from where they are today.
Q: Do you need a 64-bit OS to run 64-bit applications?
A:
Yes. Due to the way hardware is handled in our modern days, there won't be the option of launching a 64-bit app in DOS mode, as were the case with 32-bit DOS games. It has to run under an OS.
Neither is it possible to even imagine some kind of 'emulator' running 64-bit apps under a 32-bit OS, because of much the same reasons you can't ever transport a 747 jumbojet in the trunk of a car.
Q: Are there many 64-bit apps around?
A:
No, not yet, but there can't really be, until there's 64-bit PCs out there on the market, ready to run them. Intel introduced 32-bit mode with the '386 long time ago. But it really wasn't used as 32-bit much, until Win95 and Linux came along much later. But there wouldn't have been any Win95 or Linux, without 32-bit cpus out there, ready to run them.
Q: Is there any 64-bit OS available?
A:
Yes, there's a beta version of WindowsXP64, that works pretty ok. And there's Linux of course.
Q: Why should anyone buy a 64-bit processor now then?
A:
For right now, primarily as a fast 32-bit cpu, with a 32-bit OS. Same as '386 and '486, in the old days, which were mostly used as fast 16-bit cpus.
But this time, migration could be much faster. Reason is need. The number of developers for the iAMD'86-64 ISA passed 1000, on the 11 of February '04.
Games, Tech/Engineering, 3D modeling and various Cinematic applications will lead the way. And there's currently a growth of demand in x86-64 servers and workstations.
Q: Is 64-bit about processing larger/wider chunks of data at time, thus increasing performance?
A:
- Oh NO! - Not much anyway. No matter how many times this is repeated by PC-rags, journalists, analysts or whatever authorities people tend to trust. - This is just something that is commonly assumed.
The AMD K8's internals are universally generalized to at least 64bit width.
But data widths will generally be pretty much the same as in 32-bit cpus today.
Character is 8bit or 16bit (unicode).
Integer still defaults to 32 bit, even if integer registers are now 64bit wide and can handle 64 bits..
Fp is still 32bit and 64bit (double precision).
Vectors also remain, for now, 64 and 128bit.
Now, on the other hand: The instructions' address fields, used to refer to location of data, is 64bit instead of 32bit. This is the difference!
Software pointers are 64 bit long, instead of 32 bit. To handle pointer arithmetic efficiently, integer registers are 64 bit wide.Of course, if you need to handle very long integer fields, like in encryption, the 64-bit integer registers and operations are going to enhance performance. But really, they are there mostly to handle pointers.
Q: But 64-bit will be faster, right?
A:
Yes, somewhat faster.
Q: But why then?
A:
Because new addressing needs a new ISA, new binaries. Since we have to define a new instruction set anyway, might as well make it a little bit more modern, clever and rational than Intel's old '86 ISA. So we've got more flexible registers, more of them, and instructions making use of them. In 64-bit mode that is. That's one reason why it will be faster. Another reason is that memory mapping is simpler and more streamlined.
Some early ports hint at 30-50% improvements, but this is really up to the compiler's ability to optimize for the additional registers.
Q: Is that why 64-bit cpus run 32-bit code faster?
A:
No. 32-bit applications run on AMD'86-64 processors just like on 32-bit processors, with all the same limitations. The reason AMD's 64-bit cpus are so fast, even on 32-bit mode, is that they're a new generation of processor technology, K8 core, that is more efficient and higher performing. Again it's analogous to the old '386 and '486, that were faster than '286 in 16-bit mode, for exactly the same reason.
Q: Will we need 64-bit applications then, if it's only "somewhat" faster?
A:
- Oh, big YES. Definitly!
32 bits can only address 4GB. (without a terrible segmented memory model noone wants)
There's a 2GB memory limit imposed on 32-bit Windows apps! This is not just a limit on ram, it's the absolute limit of the virtual memory model available to an app. So it's quite serious. Remember, that a virtual memory map is highly fragmented.
For all the bullshit from Intel and the likes of tomshardware, pretending 32-64 bits is no issue, the harsh truth is that PC computing will go nowhere on 32 bits. We absolutely need 64-bit to move on.
Consider the old 640KB limit of 8086. This is where we are again today.
And it's not just the application. The hardware, OS and it's various objects, also need to be mapped into other sections of the 32 bit's 4GB space. An increasingly advanced OS also needs more mapping space to the app.
Q: But the PC managed to get by with Windows16 for many years, while Mac and others were 32-bit. Won't it be the same this time?
A:
No. The 16-32 bit migration and 32-64 bit migration are two completely different aspects of addressing technology. 16-32 bits were about moving from a segmented addressing model to a flat linear 32-bit memory model. While 16-bit computing was contorted, slow and buggy, it could well perform the type of tasks that were feasible on the amounts of RAM that were affordable in those days. We're talking about 2 - 16MB.
This is not the case now. Both 32 and 64 bit are linear addressing. This time it's about the size of the memory model. And while you could have a 16-bit Photoshop on Windows3.11, even while a 32-bit version performed better on a Mac, that won't be the case with 32/64 bit. There is no chance of a 32-bit app being able to perform the kinds of tasks that 64-bit computing will bring. A segmented 32-bit might, but you're not going to see that, because noone wants to code them. And why should they? When 64-bit is an option?
Q: When are we ready to migrate to 64-bits?
A:
- Well, we still need the apps to make use of it, ok? But in general terms, like yesterday. We're late. For all their market bullshit again, protecting their P4s and Itanium, Intel originally intended the desktop to migrate in like 2002-03. But they didn't get their cpu stuff together. Got caught up in a GHz cpu war with AMD and figured the P4 was the right answer for that. Now we will migrate while banging our heads into the 2GB barrier, rather than before, in good time and comfort.
Q: But why would we need all that memory. Isn't it just for bloatware?
A:
No. Explained in detail it goes like this:
The software and forms of use of the PC, that are available at any given time, are defined by memory needed for models/objects being handled.
Thus, simple writing, editing, calculating could be done on a 16-64KB CP/M text only display 8-bit PC.
There were lots of people around at the time who figured 128KB and 8 bits were enough for all PC use forever. But that is just because they couldn't fit into their mind to use computers as WYSIWYG publishing tools. Or editing pictures. (-"Photographs in a computer? - Ho, it would need like a MEGABYTE ram for graphics!")
Creating/editing music and sound. Rendering realistic images. Editing video. Solid modeling. Physics simulations. Voxel handling/displaying (Adam & Eve, CAT-scan etc).
All these new uses for the computer came about as the necessary amounts of memory became available.
So it's ultimately the price of RAM and harddrives that dictates what we will use a computer for.
So, take a good look at that limit of about 1.5-1.8GB (practical, remember fragmentation) and compare to prices on RAM and capacity of harddrives. And compare it to how much memory (Including swap. It's important to understand that it's about the size of the virtual map. Not just ram!) you yourself tend to use today. And by all means, how much recent games require. Then, looking backwards for historical guidance, try figure where we will be in 12-18 months.
Q: So what's the memory limit for 64-bit code then?
A:
Well, for x86-64, the virtual space to rumble around in, is fully 16 ExaBytes.
But "only" 4 PetaBytes in that space can be mapped, so that's the limit.
However, that is for AMD'86-64 as such, not for the current K8's.
Current K8's have 256 Terabytes space to rumble around in, but "only"
a total of 1 TeraByte can be mapped, so that's the limit of virtual memory. But again, the space is much bigger, which should be a help for many things, including fragmentation.
Even further limiting is WindowsXP64´addressing scheme, which I understand will give you 'only' 16 Terabyte virtual space, and initially map to only 16GB.
One ExaByte is 1024 PetaBytes.
One PetaByte is 1024 TeraBytes.
One TeraByte is of course 1024 GigaBytes, which you might already be familiar with.
More immediately, current implementations of iAMD'86-64 processors, both AMD and Intel, are of course more limited in physical address space. In case of AMD, the most constrictive component is the integrated memory controller (currently 16GB). Opterons can use other Opterons memory controllers over HT links to access 128GB. Intel implementations too, might have some issues beyond 4GB (sofar). But the important thing is that the software memory model is not limited. It will have enough addresses.
Q: So we're not likely to see 128-bit or 96-bit addressing soon then?
A:
No, if it happens at all in our lifetime, we're probably going to be in a state where we don't care much anymore anyway.
We are most certainly though, going to see increased widths of paths and vector processing though. This is the width that is intuitively mostly mistaken for being the "bit -issue". Take for instance the case of marketing game consoles. Currently, on the PC, on our "32-bit" cpus, that width is 128-bits. But this might increase to 256, 512, 1024... on "64-bit" cpus.
Q: When should I get a 64-bit system?
A:
Well, it's up to you. Depending on your uses, you'll probably get by on 32-bit, two years more. Beyond that, I can't say. I think it depends a lot on when MS rolls out XP-64ed.
One advantage of a 64-bit system is that it will eventually be useful for running 64-bit apps. Like getting a '386 instead of a '286, if you remember those days.
Still, maybe one should consider this as a question of what level of 32-bit performance you'd like to pay for. Just like any other ordinary PC purchase.
It's not like you're really paying anything extra or premium prices for unused 64-bitness. Today, you basically only gives up hyperthreading, by going 64-bit (AMD).