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- Newsgroups: comp.os.mach
- Path: sparky!uunet!mcsun!ieunet!tcdcs!unix1.tcd.ie!mcrosbie
- From: mcrosbie@unix1.tcd.ie (Mark J. Crosbie)
- Subject: Re: multi processor 386 and mach
- Message-ID: <mcrosbie.714068043@unix1.tcd.ie>
- Sender: usenet@cs.tcd.ie (NN required at ashe.cs.tcd.ie)
- Nntp-Posting-Host: unix1.tcd.ie
- Organization: Computer Science, Trinity College Dublin
- Date: Mon, 17 Aug 1992 16:14:03 GMT
- Lines: 62
-
- In <1992Aug13.231230.15155@cbnewsd.cb.att.com> bgbg@cbnewsd.cb.att.com (brian.g.beuning) writes:
-
- >Like many people, I have been considering getting
- >a 386 box just to be able to use mach (and UNIX and DOS).
- >So I keep checking the prices on the latest fast 486
- >machines.
-
- >But wait a minute, isn't the point of mach supposed
- >to be that it is meant for a multiple processor
- >machine? So instead of getting a fast 486, shouldn't
- >I get a cheap 386 that has more than one CPU in it
- >and get more than the performance of a fast 486?
-
- >So my questions are:
- >1. Does Mach support more than one processor on a 386?
-
- >2. Are there any cheap (or reasonable) machines for
- > sale that can be configured with more than
- > one CPU?
-
- > Thanks for an info,
- > Brian Beuning
-
- Hi Brian,
-
- Mach does indeed support more than one processor in a system,
- it was one of the design goals of Mach that it could run in parallel
- systems with multi-processors. The kernel contains a lot of locking
- structures for ensuring that the data structures in the kernel are
- updated cleanly etc.
-
- However, to actually run Mach on a multi-processor system, you have to
- buy a multi-processor machine which Mach supports.
- I'm working on a Mitac 4280G/MP which implements the Corollary Bus
- architecture in it's own wonderful way. The Corollary Bus is a
- proprietary multi-processor bus which allows multiple processors to run
- and ensures cache-coherency between them all.
- Mach recognises this by havign the pre-processor symbol CBUS defined
- in the kernel code.
-
- It also recognises Sequent Symmetry, Intel Hypercube, Compaq Systempro,
- Vax, mips and plain uni-processor 386 machines.
-
- Simply put, to buy a machine with more than 1 386 would be very
- expensive as you would be paying for the multi-processor bus which would
- have to be quite complex if caches were used on each board.
- It would also have to be recognised by Mach, as each bus implementation
- is different. If Mach didn't support it, you could forget it!
-
- In my humble opinion, it's a lot simpler to buy a FAST (50Mhz) 486
- machine with a fast
- SCSI disk and lots of memory to run Mach (>8 MB) than it is to buy
- a multi-processor system.
-
- Hope this helps,
-
- Mark Crosbie mcrosbie@ashe.cs.tcd.ie
- Computer Architecture Group
- Trinity College, Dublin
- Dublin 2
- Ireland.
-
-