- Joined
- May 7, 2004
- Location
- naples, fl
looking through the latest edition of maximum pc i found an article about an intel 64bit processor. Tom Halfhill stated in the article "intel finaly admitted that its long rumored 64bit extentions for the x86 are real and coming soon. but intelss disclosure raises new questions: How do intels extentions compare with amds? are the two 64bit architectures fully compatible with eachother?
to find answers, I spent a week slogging though the 64bit programming manuals from each company and interviewing their engineers. among other things, i compared their 64bit instruction sets, register files memory addressing schemes, context swithcing behavior, interupt handling, and support for 16-and 32-bit execution modes.two conclusions emerged: its apprent intel patterned its 64 bit architecture after amd64; and, with a few exceptions the architectures are virtually compatible.
intels 64 bit x86 architecture is called extended memory 64 technology (EM64T). although prescott has em64t its not activated in current versions of the processor. instead, em64twill officially debut in the Nocona xeon chip for dual processor servers, due to ship before june 30. amd64 processors have been shipping since early 2003.
because 32 bit x86 processors already have extended memory addressing beyond 32 bits. em64t and amd64 define even more adress bits but the mmost significant extensions are new 64 bit instructions and registers, plus some additonal 128 bit registers for media insturctions. (registers are temporary internal memry slots used by programmers.my analysis revealed that em64t and amd 64 have identical register files and nealy identical insturction sets. the differences come down to seven instructions. one instruction is unique to intel, and the other six are supported by both companies, but not always in the same execution modes.
Hence intles reluctance to gurantee that 64 bit software will always be compatible with 64 bit architectures although intel does promise to run the smae 64 bit operating systems as amd64. indeed future versions of em64t and amd64 will probably resolve their minor differnces and become 100percent compatible"
to find answers, I spent a week slogging though the 64bit programming manuals from each company and interviewing their engineers. among other things, i compared their 64bit instruction sets, register files memory addressing schemes, context swithcing behavior, interupt handling, and support for 16-and 32-bit execution modes.two conclusions emerged: its apprent intel patterned its 64 bit architecture after amd64; and, with a few exceptions the architectures are virtually compatible.
intels 64 bit x86 architecture is called extended memory 64 technology (EM64T). although prescott has em64t its not activated in current versions of the processor. instead, em64twill officially debut in the Nocona xeon chip for dual processor servers, due to ship before june 30. amd64 processors have been shipping since early 2003.
because 32 bit x86 processors already have extended memory addressing beyond 32 bits. em64t and amd64 define even more adress bits but the mmost significant extensions are new 64 bit instructions and registers, plus some additonal 128 bit registers for media insturctions. (registers are temporary internal memry slots used by programmers.my analysis revealed that em64t and amd 64 have identical register files and nealy identical insturction sets. the differences come down to seven instructions. one instruction is unique to intel, and the other six are supported by both companies, but not always in the same execution modes.
Hence intles reluctance to gurantee that 64 bit software will always be compatible with 64 bit architectures although intel does promise to run the smae 64 bit operating systems as amd64. indeed future versions of em64t and amd64 will probably resolve their minor differnces and become 100percent compatible"
