Date: Thu, 28 Oct 1999 23:41:28 -0400 (EDT) From: John Baldwin <jobaldwi@vt.edu> To: Chuck Youse <cyouse@paradox.nexuslabs.com> Cc: hackers@FreeBSD.ORG, Julian Elischer <julian@whistle.com>, Matthew Dillon <dillon@apollo.backplane.com>, Michael Beckmann <petzi@apfel.de>, Mike Smith <mike@smith.net.au> Subject: Re: Limitations in FreeBSD Message-ID: <199910290341.XAA00750@server.baldwin.cx> In-Reply-To: <Pine.BSF.4.10.9910282319290.4247-100000@paradox.nexuslabs.com>
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On 29-Oct-99 Chuck Youse wrote: > >> > That´s why I´m looking for a way of having large mmap´able >> > files. Are you saying that ALL Intel CPUs, including PIII, can >> > only >> > address 4 GB? >> >> That's correct; it's why the ia32 architecture has a '32' in its >> name. > > I don't believe that's true. I don't have any hard evidence within > easy > reach, but with the introduction of the Pentium, the address space > was > increased. A user process, of course, can only have 4G of > addressible > space (32-bit addresses) but the OS can map pages of the 4G space > into a > larger area. It was the PPro, not the Pentium, and it is called Page Address Extensions.. it does some funky stuff with the page tables to gain an extra 4 bits for a total of 64 gig of addressable space. It ends up using 4k and 2mb pages. > Something to do with 4MB pages instead of 4K pages. This is a seperate issue known as Page Size Extensions and actually was present in some i486dx4/100's. Basically, it allows you to directly map 4mb with a single page entry by leaving out the bottommost layer of the page tables. > Again, I could be wrong on this one. > > Chuck Youse --- John Baldwin <jobaldwi@vt.edu> -- http://www.cslab.vt.edu/~jobaldwi/ PGP Key: http://www.cslab.vt.edu/~jobaldwi/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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