Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!uunet!mcsun!hp4nl!phigate!philica!adrie
From: adrie@philica.ica.philips.nl (Adrie Koolen)
Newsgroups: comp.os.minix
Subject: Re: minix on 486 PCs
Message-ID: <823@philica.ica.philips.nl>
Date: 13 Jun 91 07:52:39 GMT
References: <56063@nigel.ee.udel.edu>
Reply-To: adrie@beitel.ica.philips.nl (Adrie Koolen)
Organization: Philips TDS, Innovation Centre Aachen
Lines: 67

In article <56063@nigel.ee.udel.edu> EOAHMAD%NTUVAX.BITNET@cunyvm.cuny.edu writes:
>Softwarewise 486 is similar to 386 so PC minix would have no problem with
>486 but 486 is not just a 386 with better cache. It is a much improved 386.
>486 has managed to implement most of the commonly used instructions in just
>one cycle, so that it is slightly faster than SPARC RISC microprocessors ath
>the same frequency of 25MHz.

I must by saying that I'm no 486 expert, but if I've understood it well,
the `one cycle' is execution time. Of course, the instruction first has to be
fetched from cache or external memory (which can also be externally cached).
Only when fetched from the internal cache, the pipeline is not stalled.
I don't know how fast a burst mode memory access is. Maybe someone can clarify.

>In the IEEE MICRO FEB 1990
>The geometric mean of the standard SPEC benchmark suite consisting of
>gcc, espresso,eqnitott, the 486 has 13.0 versus 12.2 for SPARC and 19.6 for
>MIPS.

Are you sure that both processors mentioned run at 25MHz? I doubt that!
Not that I want to praise my SparcStation IPC into heaven, but in general
tests, my 25MHz SparcStation IPC is as fast as a 33MHz 486, of course
depending on the speed of the disk subsystem, etc. On some tests, the 486
is faster, in other tests the Sparc. Anyway, I've yet to meet the PC expert,
who can sit behind an unknown PC, work for an hour with MS windows,
Borland C++ and WordPerfect and tell exactly what processor on what speed
is in it and what the seek and data transfer numbers of the disk are :-)

>Surprisingly, I find that the Sun Sparc Station 1, even without windows,
>at 25 Mhz is so slow at screen updates compared to Minix on my 386/25 without
>cache with  super VGA display.

I think you're comparing apples with oranges. The SparcStations have a frame
buffer with only one display mode, which is bit-mapped. They're not designed
for fast text scrolling. I've recently compared the speed of the graphical
display systems of my color SparcStation and 33MHz 386 PC with super VGA in
1024*768*256 mode under MS Windows. I looked at display operations like
refreshing the screen and copying rectangular areas on the screen. The
SparcStation managed to copy some 4MB per second (scrolling in an xterm
window), the PC stopped at 500KB per second. If you've used MS Windows at
this resolution, you'll know that it's terribly slow on display operations.
That's not the fault of the 33MHz 386 nor the ET4000 VGA chip, but from the
AT-bus.

BTW. Framebuffer access on the SparcStation IPC takes some 7 cycles, so you
can access 4 pixels (32 bits) more than 3 times per us.

>Minix is even faster than DOS.

I won't argue on that, but such a generalized statement doesn't say much.
If the systems running dos and running Minix were compareble, then you've
got a point, but so many programs only run under dos and not under Minix
that it's useless to say that "my Informix SQL database query under dos
runs more slowly that under Minix, if it would exist". Don't get me wrong,
you might be right, but don't underestimate the importance of the availability
of applications under certain operating systems!

>The Berkeley Unix Sys 4.1.1 is such a burden
>to the system that it slows down everything. Minix is not only for learning
>but also for serious users who wants work done quickly.

What work??? Professional work? Database work? CAD work? Minix is a nice OS,
but don't lose your head please.
(BTW, I don't know version 4.1.1 of BSD. I guess that you mean SunOS 4.1.1.
While it is not perfect (it's BIG), it certainly is not slow in everything!)

Adrie Koolen (adrie@ica.philips.nl)
Philips Innovation Centre Aachen