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From: jds@cs.umd.edu (James da Silva)
Newsgroups: comp.os.minix
Subject: Re: MINIX on a 486?
Message-ID: <35441@mimsy.umd.edu>
Date: 11 Jun 91 02:01:50 GMT
References: <13393@mentor.cc.purdue.edu>
Sender: news@mimsy.umd.edu
Organization: University of Maryland, Department of Computer Science
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In article <13393@mentor.cc.purdue.edu> asg@sage.cc.purdue.edu
(The Grand Master) writes:
>-Will the extensions to MINIX for a 386 work equally well on a 486?

Yes, I run Minix on my AMI Voyager 486-25.  Works quite well.

>-Is a 15-20MB Ramdisk feasable?

Well, what do you mean by feasable?  There isn't any fundamental reason 
that it can't be done, but a filesystem cache would be better: 20 meg is a
lot to lose in a power outage.

>-Is anyone out there working on (or planning on) extensions to MINIX
> for a 486, or will any 486 extensions be applicable to a 386 as well.

I don't know that Minix needs to explicitly deal with 486isms.  There are a
number of differences listed between the 486 FPU and the 387 that look at
first glance that they might be significant to the operating system, so if
someone does do FP exception support in the kernel, 486 specific code might
be needed or desired.

>-Is anyone out there working on Job control, swapping&paging, and/or
> sockets for MINIX?

Why turn Minix into BSD: BSD will be free "soon".

>-Is there a higher power UNIX(tm)-like OS out there with complete source
> that would have Job Control, swapping/paging, sockets, etc?

If you can wait, BSD 4.4 should fit the bill for you.

>-I have heard that there is a 32M limit on MINIX partitions. If so, 
> 4*32=128 which would leave 72MB/drive unoccupied. Any suggestions
> on how to work around this?

The limit on Minix 1.5 partitions is 64 Meg, not 32, so with 200M disks you
are safe.  Minix 1.6 should handle larger partitions; I don't recall what
the limits are.  Ideally, the whole disk should be one partition; there's
no good reason to pigeon-hole the disk.

>-Would I be better off getting a more high-power (and more high-priced :-( )
> UNIX(tm)-like OS (propbably without the source)?

Well, what do you really want??  Minix isn't really designed for machines
with 40 megabytes of memory; after all, you can't run X on it. :-)  If you
want to run X and big lisp jobs, or support 16 users, then you will want
VM.  Thus you probably don't want Minix.  If you just want all that memory
to make up for slow disks, perhaps you should run Sprite.

>- Is there a way to split my HD into > 4 partitions? If so, what files would
>  I need to modify?

You need to modify at_wini.c.  There's nothing really sacred about the
partition table, except compatibility with current tools and OSes.  You
could probably hack at_wini.c to use a different scheme, but then you'd
need your own fdisk equivalent.  Something simple would be to ignore the
partition table and use fixed size partitions: /dev/hd1 is the first 64M of
disk, hd2 the second 64M, etc.  until you run out of disk space.  The
second hard disk could start at /dev/hd32 or whatever.

I'm not recommending this as a general solution, but it's the kind of
simple hack that can get you by on a rainy day when you are contemplating
the unused chunks of your 340 Meg SCSI disk. :-)

Jaime
...........................................................................
: domain: jds@cs.umd.edu				     James da Silva
: path:   uunet!mimsy!jds		    Systems Design & Analysis Group