Path: utzoo!mnetor!uunet!husc6!tut.cis.ohio-state.edu!rutgers!iuvax!bsu-cs!dhesi From: dhesi@bsu-cs.UUCP (Rahul Dhesi) Newsgroups: comp.unix.wizards Subject: Re: Re: Help us defend against VMS! Message-ID: <2424@bsu-cs.UUCP> Date: 20 Mar 88 17:17:50 GMT References: <695@unm-la.UUCP> <4583@garfield.UUCP> <2134@ukecc.engr.uky.edu> <3201@phri.UUCP> Reply-To: dhesi@bsu-cs.UUCP (Rahul Dhesi) Organization: CS Dept, Ball St U, Muncie, Indiana Lines: 35 In article <3201@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: > If I understand Henry correctly, he's saying that you can't port >VMS to a RISC machine. Why not? Other than it's proprietary nature, what >is there to prevent a VMS port hardware other than a vax? The VAX/VMS kernel seems to be written in some combination of assembly language and the high-level language BLISS. But BLISS is a machine- dependent language. The basic design of VMS is heavily dependent on the VAX architecture. The four VAX CPU modes (kernel, executive, supervisor, user) are everywhere assumed to exist and the security of the system relies on having these modes available. System calls assume the existence of a VAX-specific trap mechanism. Even specific address bits are assumed (I believe the high bit in the address distinguishes between user address space and system address space). Take a look at the VAX/VMS Internals handbook, and compare it with the UNIX design book by Bach. The VMS book is chock-full of information about how specific VAX registers are used and how things are pushed and popped on the stack by instructions to change mode to kernel etc., how address bits are used, how hardware-dependent tricks are used to achieve this or that. The UNIX book, on the other hand, says nothing about the hardware. The difference in philosophy is clear. The concept of separating a small machine-dependent part and a large machine-dependent part and rewriting only the small machine-dependent is foreign to VAX/VMS. Making VMS work on a non-VAX architecture would not be a port. It would be a rewrite from the ground up. VMS is an efficient, specialized dinosaur that will become extinct when the climate changes, and the climate is changing. -- Rahul Dhesi UUCP: !{iuvax,pur-ee,uunet}!bsu-cs!dhesi