Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!ames!lll-tis!ptsfa!hoptoad!academ!uhnix1!nuchat!steve From: steve@nuchat.UUCP (Steve Nuchia) Newsgroups: comp.sys.ibm.pc,comp.arch,comp.unix.wizards Subject: Re: 386 demand paged virtual memory Message-ID: <306@nuchat.UUCP> Date: Thu, 3-Sep-87 23:21:54 EDT Article-I.D.: nuchat.306 Posted: Thu Sep 3 23:21:54 1987 Date-Received: Sun, 6-Sep-87 01:50:51 EDT References: <125@snark.UUCP> <299@nuchat.UUCP> <358@netxcom.UUCP> Organization: Public Access - Houston, Tx Lines: 39 Summary: what else one would need Xref: mnetor comp.sys.ibm.pc:7496 comp.arch:2096 comp.unix.wizards:4099 In article <358@netxcom.UUCP>, jallen@netxcom.UUCP (John Allen) writes: > In article <299@nuchat.UUCP> steve@nuchat.UUCP (Steve Nuchia) writes: > > meaning for those words? I didn't think the 386 > > had the hardware for real demand paging, am I wrong? > > The 386 processor has: > > 64 terabytes of virtual address space, > A page fault interrupt (14), > and > A restartable instruction set (two avoidable exceptions). > > What else would one need? Several people sent me lots of good info by mail, for which I am grateful. I really should keep up with such things, but there is so much to read and so little time.... In addition to the things you list, one needs a virtual-to-physical address translation mechanism. If this had been required to be off-chip, as I had though it was, we could expect the mass market (affordable) 386 products to leave it off. The answers, for anyone still curious, are that the 386 does include, in addition to the above, a small-ish page table cache which hardware keeps track of using a ram-resident page table/process descriptor type thing. I don't know much of the detail, but I do know that the bare chip has sufficient (specified) capability for real demand paging. I also found out that microport is _still_ not shipping unix for the 386. *sigh* Steve Nuchia -- Steve Nuchia Of course I'm respectable! I'm old! {soma,academ}!uhnix1 Politicians, ugly buildings, and whores !nuchat!steve all get respectable if they last long enough. (713) 334 6720 - John Huston, Chinatown