Date: Fri, 20 Nov 1998 00:52:36 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: dillon@apollo.backplane.com (Matthew Dillon) Cc: Marius.Bendiksen@scancall.no, tlambert@primenet.com, rnordier@nordier.com, freebsd-hackers@FreeBSD.ORG Subject: Re: FreeBSD on i386 memory model Message-ID: <199811200052.RAA21672@usr09.primenet.com> In-Reply-To: <199811181842.KAA06180@apollo.backplane.com> from "Matthew Dillon" at Nov 18, 98 10:42:50 am
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> On the 386 and 486, call gates are faster. On the pentium, pentium-PRO, > and pentium-II, interrupts are faster. > > Argument copying is wasteful and has limited use on systems where the > supervisor has access to the user mode memory map. FreeBSD (and virtually > all other operating systems) uses a two-layer design, not a multi-layer > ring design. About the only thing you might see different between OS's > is that some processors have a separate 'interrupt stack'. On Intel cpu's, > however, the abstraction is useless due to the completely broken ring > design because many supervisor instructions only work in ring 0. ring 1 > and ring 2 are almost completely useless. It is useful for the utilization of Windows VxD's in whatever kernel that whatever kernel support putting the Windows VxD's in a seperate VM space. This is also useful for NetWare NLM's. Not that anyone would want to leverage billions of dollars of commercial developement to save a few decades of driver writing... Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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