Intel Extended Memory 64 Technology

[Rakdos]

Does Intel Extended Memory 64 Technology (EM64T) make a processor 64-bit, because i was looking at the Pentium 840 (3.0 Ghz Dual-core) and noticed that was on the list of features.

 

thanks

[5614]

http://www.intel.com/technology/64bitextensions/faq.htm

 

It seems to be an enhancement allowing processors to run 64-bit code.

 

I'm uncertain whether computers will generally fun faster with this extension or not. They will be able to run 64-bit applications though.

[bascule]

EM64T is Intel's implementation of AMD64, which is a set of 64-bit extensions for IA32.

 

Since AMD64 has 8 general purpose registers instead of the 4 of IA32, in general code compiled for AMD64 runs approximately 30% faster than IA32.

[5614]

So does the EM64T which is an extension to a 32-bit processor make the processor actually run faster? Or does it just allow it to run 64-bit code if required? Or does it make all code 64-bit?

[1veedo]

It's just an emulator. The Linux kernel I know has had the ability to emulate 64bit, and a number of other things, for quite a while. I remember having to set some special thing on my old computer that emulated a pentium from a celoron (the special math functiosn that the celeron doesn't have). This doesn't make it faster, at all. Actually it'll slow it down some. For example of the math functions, instead of the processor being able to auto-run the special functions, there is an extra software level that uses the CPU to spit back the pentium specific responses.

 

You might as well use 64bit though, because it's a lot easier to "emulate" 32 bit from 64. For instance, flash / shockwave will not run on 64 bit. But you can install 32 bit Firefox on 64 along side the 64 bit version. You just ./configure with the --libdir=/usr/lib32 option -- assuming you've installed all the 32 bit libs along side the 64. I've also heard of people chrootting an entire 32 bit install inside their normal install.

 

http://gentoo-wiki.com/HOWTO_AMD_64#Macromedia_Flash_and_Java_Under_AMD64_with_firefox

[bascule]

So does the EM64T which is an extension to a 32-bit processor make the processor actually run faster?

 

No, but with 8 general purpose registers, your CPU wastes a lot less time shuffling values around when it runs out of register space. That's where the 30% speed boost comes from, but again, that's only for AMD64 code designed to make use of the extra 4 registers.