Messages in this thread | | | From | (H. Peter Anvin) | Subject | Re: using more than 2 GB as a ram disk | Date | 3 Feb 1999 23:22:47 GMT |
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Followup to: <199902031830.NAA09100@saturn.cs.uml.edu> By author: "Albert D. Cahalan" <acahalan@cs.uml.edu> In newsgroup: linux.dev.kernel > > The compiler must be hacked to use a 64-bit model, with pointers > normallized. The low 32 bits of a pointer would only hold 23 bits > of the address space; the other 13 bits are the segment. This hack > was fairly common for DOS software, not something I dreamed up. > > Yeah, this is slow. Every memory access needs a segment override. > The job gets done though: true flat-memory 64-bit software on ia32. >
Hardly "true flat-memory 64-bit"; it is a hacked 36-bit model where you either store pointers in a non-flat format or normalize them every time; once (or if) Intel adds more adds more address bits than 36 you're hosed again.
Not to mention the cost to load segments for every reference.
-hpa -- "Linux is a very complete and sophisticated operating system. There are, and will be, large numbers of applications available for it." -- Paul Maritz, Group Vice President for Platforms And Applications, Microsoft Corporation [Reference at: http://www.kernel.org/~hpa/ms.html]
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