latest current fails to mount root

[Greg Troxel <gdt%ir.bbn.com@localhost>]

I just rebuilt current for i386 and updated two notebooks.  One is fine,
and the other won't boot, failing to find the root partition.  (current
from a week ok worked fine.)  It printed something about mbr partition
extending beyond physical disk size after the kernel had probed devices,
and was then in 'choose root device' mode.  I couldn't find the msg in
the source so will boot it again and get the exact message.

On this machine, I think the mbr is ok:

foobar gdt 11 /usr/home/gdt > dmesg|egrep wd0
wd0 at atabus1 drive 0: <HTS541010G9SA00>
wd0: drive supports 16-sector PIO transfers, LBA48 addressing
wd0: 95396 MB, 193821 cyl, 16 head, 63 sec, 512 bytes/sect x 195371568 sectors
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100)
wd0(ahcisata0:0:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100) 
(using DMA)

Disk: /dev/rwd0d
NetBSD disklabel disk geometry:
cylinders: 193821, heads: 16, sectors/track: 63 (1008 sectors/cylinder)
total sectors: 195371568

BIOS disk geometry:
cylinders: 1023, heads: 240, sectors/track: 63 (15120 sectors/cylinder)
total sectors: 195371568

Partition table:
0: NetBSD (sysid 169)
    bootmenu: foobar
    start 63, size 195371505 (95396 MB, Cyls 0-12921/95/63), Active
1: <UNUSED>
2: <UNUSED>
3: <UNUSED>
Bootselector enabled, timeout 10 seconds.

so that fits exactly.

foobar gdt 13 /usr/home/gdt > disklabel wd0d
# /dev/rwd0d:
type: unknown
disk: HTS541010G9SA00
label: 
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 16
sectors/cylinder: 1008
cylinders: 193821
total sectors: 195371568
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # microseconds
track-to-track seek: 0  # microseconds
drivedata: 0 

16 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:   1572801        63     4.2BSD   1024  8192 43768  # (Cyl.      0*-   1560*)
 b:   4718592   1572864       swap                     # (Cyl.   1560*-   6241*)
 c: 195371505        63     unused      0     0        # (Cyl.      0*- 193820)
 d: 195371568         0     unused      0     0        # (Cyl.      0 - 193820)
 e: 189080112   6291456     4.2BSD   2048 16384 28952  # (Cyl.   6241*- 193820)

It's a thinkpad T60, but I don't think that matters.