For Whom Prefers Details On x86-64


By Nils Dahl

Date: July 27, 2002

Dave Feustel has pointed me in a very useful direction. There are very fine information sites on the fine details of Hammer's software side. http://www.x86-64.org/ is a site sponsored and supported by AMD. Look for Linux implementations and links to AMD's programmer manual set (3 volumes) here.

http://www.cpuid.org/ is the classic site for details on processor details. Nice link to x86-64 on the home page.

http://www.sandpile.org/ is another top site for processor details.

 I do not expect to see anything on the finest details of x86-64  architecture released in any form except under NDA - and those details will change as the line of processors evolve. But it would be nice to see a white paper on the basics, extending the understanding of inner workings well beyond the block diagrams that just provide a functionality overview.

If I confused anyone by comparing the 8086 memory segment design to AMD's Hammer memory, which uses a sort of segmented memory block approach to managing addressing of all available blocks, I apologize. I will attempt to delve into AMD's XMM technology, as described in Volume 3-2 of the Opteron programming guides, if or when I get a copy. Meanwhile, I will stock up on aspirin.

You may also try visiting



http://www.hardwaresite.net/x86-64.html - interesting comments. Including this quoted passage "The long mode is also divided into two sub-modes: the 64-bit mode and the compatible mode. These two sub-modes are controlled by the D and L bits, present at the descriptor pointed by the CS (Code Segment) register. The compatible mode is interesting because it allows, as a program, to run 16- or 32-bit applications inside the 64-bit mode. It is something similar to the virtual mode 86 of the 386 processors."

Use the search arguments "x86-64", "AA-64", "K-8" and append qualifiers. Oddly enough, while freeBSD has a site section dedicated to x86-64 porting, SuSe does not appear to have such a dedicated section. This might be due to everything being managed under the x86-64.org central site - so please start there for current details on os ports.

nils dahl

just an old man


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