A while ago I sent out this message (a bit edited....)

According to blymn:
>
>Folks,
>        Some of you may remember I complained about my machine
>crashing before on this list.  The advice was to get a later version
>of NetBSD.  I took this advice and have NetBSD 1.0 on my machine.  The
>bummer was that my machine still crashed when I thrashed the SCSI
>disks.  These were the errors I was getting:
>
>vmfault(f86bea00, 0, 1, 0) -> 1
>fatal page fault in supervisor mode
>trap type 6 code 0 eip f8123aff cs 8 eflags 10292 cr2 12 cpl 0
>panic: trap
>syncing disks ...
>sddump()   -- not implemented
>vmfault(f86bea00, 7ffff000, 1, 0) -> 1
>fatal page fault in supervisor mode
>trap type 6 code 7fff0000 eip f8129adb cs f8120008 eflags 10246 cr2 7fffffff cpl f8129a5c
>panic: trap
>
.... snip snip snip ....
>
>Machine details:
>
>486DX/25Mhz Micronics motherboard with 16Meg (now 12Meg) of RAM
>Adaptec AHA1542B SCSI controller with Wren VII and Maxtor LXT213 disks
>DTC ESDI controller with Wren V disk
>Wangtek QIC02 QIC tape drive
>a couple of generic serial cards
>ET4000 chipset VGA card
>
>OS: NetBSD 1.0 - no patches.
>


The general consensus was that I needed to stop my motherboard
remapping the memory between 640K and 1Meg into upper memory.

This sounded logical to me so I whipped out my trusty motherboard
documentation and found there was a switch called "15M+640K - 15M+896K
Not Mapping to 640K - 896K" which sounded like just the thing.  I
flicked the switch and when I booted the BIOS memory check complained
about memory not being there which I thought was logical.  It did
mutter about mapping stuff but I chose to ignore it....  The machine
booted fine up until the message about checking for core dump and it
hung.  I reset the machine and booted single user which was fine, did
some fsck's then tried to build a new kernel (to put ddb in) and I got
a panic - ufs_ishash or something, this was on my ESDI disk that did
not give me these problems previously.  So I flicked the switch back
to where it was and things boot fine.  I have put the machine back to
16Meg coz X was making the beast swap (well, not really X but the 1/2
dozen xterm windows, xearth, remote display of wordperfect and emacs
and other such things I use when I work from home probably did it...)
so I am planning just to be gentle with the box.

In conclusion, it seems YMMV with turning the mapping off - for me it
stuffs up other things.... sigh.  Right now a P90 with on board NCR
SCSI and a PCI bus is sounding pretty good but will have to wait for a
while.

BTW the BIOS I have is a Phoenix 80486 ROM BIOS Plus Version 0.10 F9
which does not let you do much in terms of controlling the memory
mapping etc (in fact it does none of this)

-- 
Brett Lymn, Computer Systems Administrator, AWA Defence Industries
===============================================================================
"Aha!  Pronoun problems.  It's not `shoot you, shoot you', it's `shoot me,
 shoot me'.  So, go ahead, shoot ME, shoot ME <BLAM>... You're Despicable"
                        -- Daffy Duck