x86 extensions and their compatibility?

Hi all,

I have been seeing items in articles that have prompted
several questions about the differences between AMD's
x86 extensions and Intel's x86 extensions.

Will AMD Opterons and Intel EM64T enabled chips
run the EXACT same op code set?

If there is a difference between the two then software
suppliers will have three choices under which to release
their products: common, amd variation and the intel
variation.

Is anyone familiar with this scenario? and what op codes
each one runs?

thanks,
charles....

***** charles wrote:
Hi all,

I have been seeing items in articles that have prompted
several questions about the differences between AMD's
x86 extensions and Intel's x86 extensions.

Will AMD Opterons and Intel EM64T enabled chips
run the EXACT same op code set?

Yes, the opcodes are exactly the same.

If there is a difference between the two then software
suppliers will have three choices under which to release
their products: common, amd variation and the intel
variation.

Most applications software will not need special versions at all -- they
aren't affected by any of the minor differences. The only type of
software that might be affected are operating systems.

And operating systems kernels can usually deal with the differences by
simply having a few inline "if ... then ..." conditions which take care
of it on the spot. The differences exist not because of opcode
differences but because of hardware implementation differences. For
example, there is talk that certain Intel chipsets won't allow DMA
access beyond the 32-bit boundary, even though the processor itself can
address more than that, while AMD chipsets have no such restrictions.
The OS would then have to detect what chipset it is running on, and
allocate a DMA buffer appropriately.

These implementation differences existed even on 32-bit x86, but they
are getting fewer as time went on.


Yousuf Khan

"Yousuf Khan" wrote in message
...
***** charles wrote:
Hi all,

I have been seeing items in articles that have prompted
several questions about the differences between AMD's
x86 extensions and Intel's x86 extensions.

Will AMD Opterons and Intel EM64T enabled chips
run the EXACT same op code set?

Yes, the opcodes are exactly the same.

If there is a difference between the two then software
suppliers will have three choices under which to release
their products: common, amd variation and the intel
variation.

Most applications software will not need special versions at all -- they
aren't affected by any of the minor differences. The only type of
software that might be affected are operating systems.

And operating systems kernels can usually deal with the differences by
simply having a few inline "if ... then ..." conditions which take care
of it on the spot. The differences exist not because of opcode
differences but because of hardware implementation differences. For
example, there is talk that certain Intel chipsets won't allow DMA
access beyond the 32-bit boundary, even though the processor itself can
address more than that, while AMD chipsets have no such restrictions.
The OS would then have to detect what chipset it is running on, and
allocate a DMA buffer appropriately.

These implementation differences existed even on 32-bit x86, but they
are getting fewer as time went on.

Would an implementation/recompile with Gentoo be different between a
dual opteron motherboard and a dual xeon em64t motherboard?

charles.....

***** charles wrote:
These implementation differences existed even on 32-bit x86, but they
are getting fewer as time went on.


Would an implementation/recompile with Gentoo be different between a
dual opteron motherboard and a dual xeon em64t motherboard?

Well, Gentoo is an extremely configurable Linux, the whole idea behind
it is to customize it to the level of silliness. So yes, Gentoo could be
made so customized that it won't work on any other x86 except the one it
was meant for. They customize Gentoo to even remove hardware conditionals.

Yousuf Khan