After borrowing a Seagate ST32550N (masquerading as a `SUN2.1G'), I tweaked
the esp driver a bit to make at least one instance of the infamous
"DMAWAIT panic" go away.

I invite anyone who has seen this before to try out the modifications on
other disks.

The selection failure on some disks remains. These are the probe msgs
on my IPC after hooking up all disks I could find...

...
dma0 at sbus0 slot 0 offset 0x400000: rev 1
esp0 at sbus0 slot 0 offset 0x800000 pri 3: ESP100A 25Mhz, target 7
scsibus0 at esp0
esp0 targ 0 lun 0: <SEAGATE, ST32550N SUN2.1G, 0412> SCSI2 0/direct fixed
sd3 at scsibus0: 2048MB, 3511 cyl, 11 head, 108 sec, 512 bytes/sec
esp0(2,0): MSGIN failed; trying alt selection
esp: resetting SCSI bus
esp0: stray interrupt
esp0 targ 2 lun 0: <FUJITSU, M2622S-512, 0304> SCSI2 0/direct fixed
sd2 at scsibus0: 314MB, 1429 cyl, 7 head, 64 sec, 512 bytes/sec
esp0 targ 3 lun 0: <MAXTOR, LXT-213S SUN0207, 4.17> SCSI1 0/direct fixed
sd0 at scsibus0: 202MB, 1310 cyl, 7 head, 45 sec, 512 bytes/sec
esp0 targ 6 lun 0: <SONY, CD-ROM CDU-8012, 3.1a> SCSI2 5/cdrom removable
cd0 at scsibus0: drive empty
le0 at sbus0 slot 0 offset 0xc00000 pri 5: hardware address 08:00:20:0a:ec:62
cgsix0 at sbus0 slot 1 offset 0x0: SUNW,501-1672, 1152 x 900, rev 8 (console)