Path: utzoo!attcan!uunet!snorkelwacker!spdcc!merk!alliant!cantrell
From: cantrell@Alliant.COM (Paul Cantrell)
Newsgroups: comp.sys.mac.system
Subject: Re: Protected-mode snake oil
Message-ID: <4066@alliant.Alliant.COM>
Date: 15 Aug 90 17:31:29 GMT
References: <1204.26c2fb48@waikato.ac.nz>
Reply-To: cantrell@alliant.Alliant.COM (Paul Cantrell)
Organization: Alliant Computer Systems, Littleton, MA
Lines: 30

In article <1204.26c2fb48@waikato.ac.nz> ccc_ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University) writes:
>Frankly, I'm a little skeptical. As a regular user of both a Mac and
>a VAX/VMS cluster, I'd have to say that the relative frequency of
>crashes of the two systems, leaving aside the times I crash either
>one while debugging my own software, is something in the region of
>10:1. That is, it's not as much as 100:1.

1) A VAX cluster has *lots* more hardware to go wrong than a MAC, so some of
   those VMS crashes might be due to hardware trashing the system. Protected
   operation will only catch a few of those, the rest may well result in
   crashes.

2) A VAX cluster has *lots* more software to go wrong than a MAC. The kernel
   itself is much larger and more complex. The kernel is very asynchronous
   while the MAC OS is not.

3) A VAX cluster typically has *lots* more users than a MAC. This depends on
   how it gets used, but hundreds of users isn't uncommon for a cluster.

Add all that up, and you would expect the VAX to be crashing a hundred or
a thousand times as much as the MAC. There really isn't *that* much to go
wrong with a MAC. They're pretty simple beasts. What's causing the VMS
system to be so reliable? Partly the fact that a lot of the code gets run
in non-kernel mode where errors don't take out the system in strange and
mysterious ways (or worse, simply change some kernel data).

Either that, or DEC builds software and hardware much more reliably than
Apple. I don't really think that accounts for the difference...

					Paul Cantrell