True 64 bit CPU

[lifeblood]

One of my coworkers made the claim that the core2duo was not a 64 bit CPU while the Athlon 64 is. I told him he was mistaken, but later I started to wonder. Both processors have 64 bit extensions, but are they native 64 bit? Is one of their architectures more ?64 bit? than the others? For some reason I seem to remember that the Athlon runs but 32 & 64 bit applications natively but I?ve heard no such claim for core2duo. Is their a difference, or is it a matter of semantics?

 

[The-Noid]

Niether is native to 64bit. X86-64 is just an extension of 64 bit onto a 32 bit processor. The only true 64-bit is some Sparc, IBM, and the Itanium. The rest is just more of a generic, see more memory kind of approach. And the technology used in AMd64 processors was licensed to Intel to provide an enviroment for both processors to work under a single 64 bit OS. This provides compatability and less work for Microsoft.

Cheers.

 

[aka1nas]

Edit: nvm

 

[The-Noid]

C2D does take a hit, but it does not really matter until Vista 64 is RTM before we can see by how much.

 

[dexvx]

Originally posted by: Yoxxy
C2D does take a hit, but it does not really matter until Vista 64 is RTM before we can see by how much.

What do you mean by take a hit?

There are applications in which x86-64 performance skyrocket or LOSE performance compared to their 32bit counterparts. The general difference between the A64 and the Core2, 64bit wise is within the spread of error.

 

[zephyrprime]

Originally posted by: Yoxxy
Niether is native to 64bit. X86-64 is just an extension of 64 bit onto a 32 bit processor. The only true 64-bit is some Sparc, IBM, and the Itanium. The rest is just more of a generic, see more memory kind of approach.

The 64bit sparcs and PowerPC parts are also formerly 32bit processors with 64bit "extentions". Of the procs you mentioned, only the itanium was 64bit from the ground up.

Either way, it doesn't matter. I haven't ever seen it written anywhere that an original 64bit is somehow better than an upgrade to 64bits.

 

[dmens]

both are 64-bit, and "x86 nativity" is a nonsense catchphrase used by partisans.

does IA-32 somehow taint the 64-bit extensions? does it drag down the performance of the new operations? not at all. so who cares?

 

[cmrmrc]

Originally posted by: dexvx

Originally posted by: Yoxxy
C2D does take a hit, but it does not really matter until Vista 64 is RTM before we can see by how much.

What do you mean by take a hit?

There are applications in which x86-64 performance skyrocket or LOSE performance compared to their 32bit counterparts. The general difference between the A64 and the Core2, 64bit wise is within the spread of error.

the C2D would take maybe an average of <5% hit when running in 64bit environment.......

 

[The-Noid]

X86-64 is completely different from Itanium or Sparc architectures. Sparc was built from the ground up as well. C2D takes more than a 5% hit in 64 bit in some situations in other it increases. Just depends. C2D or Athlon 64 are not going to be the chip that makes 64 bit mainstream anyway. It will still be years for migration to 64-bit oses.

 

[Acanthus]

Its not "true" 64 bit because it cant execute IA64 code.

By the same token though, its "true" X86-64 code.

So its a horse a piece really.

Itanium is going to die off eventually.

 

[ScythedBlade]

The hits still make Core 2 Duo faster than Athlon 64 at IPC ... the thing why it takes a hit is cause it can't macrofusion with 64 bit

 

[SunnyD]

Originally posted by: Acanthus
Its not "true" 64 bit because it cant execute IA64 code.

By the same token though, its "true" X86-64 code.

So its a horse a piece really.

Itanium is going to die off eventually.

WTF? Not true 64-bit because it doesn't execute IA-64?

IA-64 has nothing to do with whether it's 64-bit or not. IA-64 is just a 64-bit instruction set (which is used on Itaniums), X86-64 is a 64-bit instruction set (derived from IA-32), the 64-bit Sparc instruction set is used on (duh) Sparcs, DEC Alpha had a 64-bit instruction set, etc., etc. They are ALL true 64-bit processors. They all have full 64-bit registers. IA-64 has nothing to do with X86-64 and viceversa. In fact, IA-64 has nothing to do with IA-32, never has, never will.

 

[dexvx]

Originally posted by: cmrmrc

Originally posted by: dexvx

Originally posted by: Yoxxy
C2D does take a hit, but it does not really matter until Vista 64 is RTM before we can see by how much.

What do you mean by take a hit?

There are applications in which x86-64 performance skyrocket or LOSE performance compared to their 32bit counterparts. The general difference between the A64 and the Core2, 64bit wise is within the spread of error.

the C2D would take maybe an average of <5% hit when running in 64bit environment.......

http://www.xbitlabs.com/articles/cpu/display/core2duo-64bit_7.html

Please, its mostly within the spread of error on non-synthetic benchmarks.

 

[myocardia]

Originally posted by: dexvx
http://www.xbitlabs.com/articles/cpu/display/core2duo-64bit_7.html

Please, its mostly within the spread of error on non-synthetic benchmarks.

Who cares? Unless you're running Linux, 64-bit is still something from the future, as far as the desktop is concerned. So, maybe a C2D takes a slight performance hit in 64-bit apps, compared to an A64/Opteron. Who cares, it will still be faster clock for clock, whether it's running 32 or 64 bit instructions.

 

[sandorski]

They are both 64bit cpus and they are both "true" 64bit. Itanium has absolutely nothing to do with defining 64bitness.

 

[Viditor]

Originally posted by: Yoxxy
Niether is native to 64bit. X86-64 is just an extension of 64 bit onto a 32 bit processor. The only true 64-bit is some Sparc, IBM, and the Itanium. The rest is just more of a generic, see more memory kind of approach. And the technology used in AMd64 processors was licensed to Intel to provide an enviroment for both processors to work under a single 64 bit OS. This provides compatability and less work for Microsoft.

Cheers.

1. They are all "true" 64-bit processors...you may be speaking of addressability, in which case none of them addresses the full 64 bits (though this is only a problem if you have system Ram measured in petabytes on each processor)

2. The pointers that some people call extensions are merely pointers that tell the processor which mode it's working in (64 bit or 32 bit or both). There is no advantage inherent to a CPU that makes being 64bit only an advantage...

3. The AMD64 systems have a very slight advantage over EM64T with large amounts of memory (greater than 4GB) because Intel's chipsets do not contain a hardware IOMMU.

 

[Acanthus]

Originally posted by: SunnyD

Originally posted by: Acanthus
Its not "true" 64 bit because it cant execute IA64 code.

By the same token though, its "true" X86-64 code.

So its a horse a piece really.

Itanium is going to die off eventually.

WTF? Not true 64-bit because it doesn't execute IA-64?

IA-64 has nothing to do with whether it's 64-bit or not. IA-64 is just a 64-bit instruction set (which is used on Itaniums), X86-64 is a 64-bit instruction set (derived from IA-32), the 64-bit Sparc instruction set is used on (duh) Sparcs, DEC Alpha had a 64-bit instruction set, etc., etc. They are ALL true 64-bit processors. They all have full 64-bit registers. IA-64 has nothing to do with X86-64 and viceversa. In fact, IA-64 has nothing to do with IA-32, never has, never will.

Thank you for the education, but i was just restating why people say the BS, i dont agree with their assertion.

 

[dexvx]

Originally posted by: myocardia

Originally posted by: dexvx
http://www.xbitlabs.com/articles/cpu/display/core2duo-64bit_7.html

Please, its mostly within the spread of error on non-synthetic benchmarks.

Who cares? Unless you're running Linux, 64-bit is still something from the future, as far as the desktop is concerned. So, maybe a C2D takes a slight performance hit in 64-bit apps, compared to an A64/Opteron. Who cares, it will still be faster clock for clock, whether it's running 32 or 64 bit instructions.

Oh you again? What part of:

"EM64T technology of Core 2 Duo processors has a positive effect on the performance in the majority of applications."

and

"Of course, there are a few applications, when Core 2 Duo work slower in their 64-bit versions than it would in their 32-bit ones. Among them are Windows Media Encoder 9 or 7-zip archiving tool, for instance. However, since the other testing participants have also lost some of their performance in these tasks, the problem is most likely to be not in the microarchitecture."

Do you not understand? A64's and Core2's lose performance in some apps, but in the majority of apps they gain a little.

 

[nyker96]

As I understand it 64bit just means size of instruction/data are 64bit width correct? I don't think A64//C2D are internally 64bit, I have heard they are 48bit address space internally, but instruction-wise takes 64bit ins. So these machines are externally 64 but uses some internal trick to process 64bit instruction/address. As to "true" 64bit, that's just a label you can define it whatever you like.