Talk:X86-64

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Contents 1 Error Corrected 2 Merging AMD64, EM64T, and x64 3 Move from AMD64 4 Paging hierarchy size 5 x86-64 or AMD64 ?? 6 History of AMD64 7 Date or year of initial linux support.

[edit] Error Corrected

Please note: This information was incorrect: "traditionally, operating systems take one half of the address space for themselves (usually the higher half, named kernel space) and leave the other to applications (user space)". It's highly unusual to put the kernel at the top. Usually it's at the bottom, below the program code and data segments, and the stack is usually at the top.

[edit] Merging AMD64, EM64T, and x64

After weeks of discussion on the Talk:X64 page, there was little opposition to merging the three articles. The biggest debate was about what the name should be: AMD64, EM64T, and x64 or something else, namely x86-64. --Charles Gaudette 21:47, 18 September 2006 (UTC)

[edit] Move from AMD64

Woah. Was there a consensus to rename this page? I for one oppose this. AMD64 is the name of the architecture, like IA-32 is the name of an architecture. AMD64 is in wide use by many linux distributions, BSD systems, Microsoft, etc, to refer to this architecture. We need a vote or a consensus on such a drastic change that seems to take neutrality overboard to the point of changing the meanings of words. samrolken 07:25, 22 September 2006 (UTC)

Are you saying you have read the comment above and the Talk:x64 discussions? And are still unhappy? --Charles Gaudette 18:56, 22 September 2006 (UTC)

[edit] Paging hierarchy size

I've just replaced a some text that misleadingly stated that a full 64-bit PML4 would be 256 MiB long. In fact, the size is right for the PML4, but I think a better impression would be given if the size of the whole page mapping hierarchy is shown. These are my results for the current 48-bit hierarchy:

• One PT: 512 entries x 8 bytes = 4096 bytes
• One PD: 512 entries x (8 bytes + size of the associated PT) = 2101248 bytes = 2052 KiB
• One PDPT: 512 entries x (8 bytes + size of the associated PD) = 1075843072 bytes = 1026 MiB
• The PML4: 512 entries x (8 bytes + size of the associated PDPT) = 550831656960 = 513 GiB

Which yields about 0.2% of the 256 TiB space. Phew! Anyone wants to try calculating this for a possible 64-bit scheme? Habbit 09:22, 9 October 2006 (UTC)

Not really. The size of the PML4 was enough to scare me. :)

By the way, do you have a source for this change:

"In implementations supporting larger virtual addresses, this latter table would either grow to accomodate sufficient entries to describe the entire address range, up to a theoretical maximum of 33,554,432 entries for a 64-bit implementation, or be overranked by a new mapping level, such as a PML5"

The AMD docs suggest PML4 will be extended, specifically this one, on page 133:

"Note: The sizes of the sign extension and the PML4 fields depend on the number of virtual address bits supported by the implementation."

Now obviously as there is no implementation with more than 48 bits available yet this is still subject to change, but I think that's a pretty clear statement that the PML4 will be expanded in such cases. Unless another source contradicts it, in which case we'll just have to wait and see... JulesH 15:07, 14 October 2006 (UTC)

I don't think that means the PML4 is to be expanded on >48b implementations. It sounds like "don't take the 48 bits for granted, could be less in some sadistic but still amd64-compliant platforms". Think about an expanded PML4 and you'll see an unmanageable 32 million entry behemoth. Habbit 18:45, 14 October 2006 (UTC)

[edit] x86-64 or AMD64 ??

Why the name has been changed to x86-64 ??

AMD stated and offically declared the rename of technology from x86-64 to AMD64...

the title for this Article must be AMD64, and any one enters x86-64 must be redirected to AMD64

The name of the page was changed to x86-64 because the page covers both AMD's implementation of the instruction set, which they now call AMD64, and Intel's implementation, which they've called, at various times, IA-32e, EM64T, and Intel64. The name x86-64 is a vendor-neutral way of referring to the instruction set, and not one specific to particular OSes, as x64 is. See Talk:x64 for the full discussion on the name change.

Given that AMD aren't the only company implementing the instruction set, the fact that they now call it AMD64 to promote their invention of it does not in any way impose any sort of requirement that the article be called AMD64, so, no, the title of this article is not required to be AMD64. Guy Harris 11:55, 14 November 2006 (UTC)

The name of the architecture is AMD64 in the same way that the name of the architecture it expands upon is i386 (i for Intel). When a company develops something, they get to name it - the fact that Intel calls their implementation of the instruction set something else is amusing, but it doesn't change the fact that the proper name to use for the architecture / instruction set in an encyclopedic work is AMD64. Chandon 02:05, 16 November 2006 (UTC)

In fact, it referred to in most literature as x86_64, not x86-64, but maybe Wikipedia conventions do not allow such a name ? If they do, a redirect from x86_64 to x86-64 could be of help for some people. 81.65.26.7 00:47, 14 December 2006 (UTC)

Did you try it? It's there (since 2004, apparently). Because of the way Wikipedia names are mapped, it's called "x86 64", but if you type in x86_64, it does the expected thing. --NapoliRoma 01:59, 14 December 2006 (UTC)

[edit] History of AMD64

It would be nice to have a history subsection of the AMD64 section. When was the technology announced for the first time? When was the first emulator available? when was the first piece of hardware available? --Jarl Friis 07:45, 26 January 2007 (UTC)

[edit] Date or year of initial linux support.

Since Linux was the first OS to run x86-64 in long mode, it would be very relevant to know when that happend, can someone tell. When and which was the first linux distribution to officially release a version with x86-64 support? I think it was SuSE, but I am not sure. --Jarl Friis 07:50, 26 January 2007 (UTC)

x86-64 support was merged into the development kernel at 2.5.5 (released 20th Feb 2002, see Changelog-2.5.5). A beta version of x86-64 SuSE was made available a few months before the actual release of AMD's first x86-64 Opterons ("Hammer") in April 2003 as per [1]. Debian merged x86-64 to Sid in mid-2004 and there was an "unofficial" x86-64 Sarge release in 2005, but as of yet, no official version (pending the release of Etch). Redhat made an x86_64 release sometime after SuSE. Andrew Rodland 23:40, 28 February 2007 (UTC)