> Warning: BIOS sector numbering starts with sector 1
> Information from DOS bootblock is:
> The data for partition 0 is:
> <UNUSED>
> The data for partition 1 is:
> <UNUSED>
> The data for partition 2 is:
> <UNUSED>
> The data for partition 3 is:
> sysid 165 (NetBSD or 386BSD)
>     start 1, size 1425311 (695 MB), flag 80
>         beg: cylinder    0, head   0, sector  2
>         end: cylinder  706, head  31, sector 63
> ---
> 
> 
> 2) Install the following disklabel (with "disklabel -w -r wd0a mywd")
> 
> ---
> mywd|NetBSD installation generated:\
>         :dt=ST506:ty=winchester:\
>         :nc#707:ns#63:nt#32:\
>         :se#512:\
>         :pa#1171296:oa#0:ta=4.2BSD:ba#8192:fa#1024:\
>         :pb#254016:ob#1171296:tb=swap:\
>         :pc#1425312:oc#0:\
>         :pd#1425312:od#0:
                      ^^^^
Mismatch with 

beg: cylinder    0, head   0, sector  2               

> 6) Now the weird part.  I intsall the bootblocks with
>    "/usr/mdec/installboot /usr/mdec/biosboot.sym /dev/rwd0a" and after it
>    completes, I end up with the following ouput from fdisk:
> 
> ---
> ******* Working on device /dev/rwd0d *******
> parameters extracted from in-core disklabel are:
> cylinders=707 heads=32 sectors/track=63 (2016 sectors/cylinder)
> 
> parameters to be used for BIOS calculations are:
> cylinders=707 heads=32 sectors/track=63 (2016 sectors/cylinder)
> 
> Warning: BIOS sector numbering starts with sector 1
> Information from DOS bootblock is:
> The data for partition 0 is:
> <UNUSED>
> The data for partition 1 is:
> <UNUSED>
> The data for partition 2 is:
> <UNUSED>
> The data for partition 3 is:
> sysid 165 (NetBSD or 386BSD)
>     start 0, size 50000 (24 MB), flag 80
>         beg: cylinder    0, head   0, sector  1
>         end: cylinder 1023, head 255, sector 63

> It looks like it's clobbering the MBR. 

OK, you have given whole disk to NetBSD, it does not need DOS partition
table, bootblock will be in first sector of the disk - at least in 1.2
disklabel does it correctly (I have not tried installboot yet).

> If I don't install the bootblocks,
> fdisk output remains as before, and a reboot off the HD predicably has 
> the result: "Missing operating system".
> 
> If I write the bootblocks, I'm back to "Read error", but it clearly has

This is the only bad thing. I think you have confused installboot
by your sector 2 partition, try to delete all partitions from MBR.


-- 
Zdenek Salvet                                              salvet@ics.muni.cz 
----------------------------------------------------------------------------
           If God had meant for us to be in the Army,
         we would have been born with green, baggy skin.