On 7/11/07, Ramagudi Naziir <naziirr@xxxxxxxxx> wrote:
hi all, can someone pls fix the mess for me ? what is the difference between IA64 and x86-64 ?
x86_64 is an ISA (Instruction Set Architecture) which extended the normal x86 ISA to support 64 bit extensions and is backwards compatible with it (This is also called AMD64 (by AMD) or EM64T (by Intel)). The differences between AMD64 & EM64T's ISA are very minor, existing only in the graphics extensions like SSE2, SSE3 in Intel & 3DNow & 3DEnchanced etc. Examples include Intel's Xeon and the entire AMD 64 bit lineup etc. In the kernel land, x86_64 means systems with processors which support this ISA, **AND** which are running in the 64bit mode. (For example you can have an AMD Athlon64 running an i386 kernel, since the processor mode would not be switched from 32bit protected mode to the 64 bit long/compatibility modes). IA64 is a completely new ISA, which is in no way related to the i386 ABI. It has a fundamentally different ISA, which is not at all backwards compatible. (Although emulations exist) It uses some VLIW (Very Long Instruction Word) techniques... I am not very sure about this. I also think this is RISC arch, unlike the IA32 & EM64T which are CISC - but the lines between both are now somewhat blurring.... Example: Itanium
and between x86, IA32, and i386,i486,i586,i686 ?
Those are just various ISAs from Intel all of which are backwards compatible with the i386 ISA. Intel wanted to trademark these names, but could not trademark a number, so after i686, Intel's Processors went with the name of "Pentium". IA32 is just a catch all for the i386 and Above ABIs.
thank you naziir
Bhanu.
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