64-bit x86 architectures from AMD and Intel are almost, but not quite, identical according to Microprocessor Report, a sister publication to Electronics News. According to the publication, this indicates that Intel has developed its own devices after reading AMD documentation and testing the smaller company’s processors.
Microprocessor Report compared memory-addressing schemes and many other architectural features, such as data-addressing modes, context-switching behaviour, interrupt handling and support for existing 16- and 32-bit x86 execution modes were also compared. In every case, Intel had patterned its 64-bit x86 architecture after AMD64 in almost every detail.
However, Microprocessor Report discovered a few differences that even AMD and Intel were unaware of. According to the publication, some of these differences may be resolved in future 64-bit x86 processors, or even in future steppings of x86 processors already announced or on the market. In other cases, software can easily adapt to the differences by executing slightly different code, after first probing the processor to learn which 64-bit extensions it supports.
“Intel’s reluctance to make a blanket guarantee about mutual 64-bit software compatibility is justified by the minor differences we discovered,” says Tom Halfhill a senior editor with the publication. “Of course, that’s always the case when Intel or AMD introduces new x86 extensions-such as Intel’s SSE3 media extensions, which aren’t yet supported by AMD.”
Despite the differences, Microprocessor Report claims “Intel clearly derived its 64-bit architecture by reading AMD’s pre-release documentation for AMD64 and by testing [processors]”.
“Intel’s reverse-engineering of [AMD’s 64-bit processors] marks a major turning point in the historical relationship between the companies,” says Halfhill. “Although AMD has in the past introduced some innovations to the x86 architecture … this is the first time AMD has truly steered the direction of the world’s most important microprocessor architecture, which Intel invented in 1978 and has closely guarded for 26 years.”
Microprocessor Report’s article, “AMD and Intel Harmonize on 64” can be found in the 29 March issue.
Further information - www.mdronline.com.