port-vax/59344: MicroVAX 3100-40 fails to boot vax install iso

[rumi%rtfm.hu@localhost]

>Number:         59344
>Category:       port-vax
>Synopsis:       MicroVAX 3100-40 fails to boot vax install iso
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-vax-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Apr 23 09:20:00 +0000 2025
>Originator:     Szabolcs Rumi
>Release:        10.1
>Organization:
>Environment:
KA45-A V1.2-343-V4.0
32MB
>Description:
NetBSD/vax 10.1 ISO:

>>> boot dka400

-DKA400
>> NetBSD/vax boot [1.12 (Mon Dec 16 13:08:11 UTC 2024)] <<
>> Press any key to abort autoboot 0
getdisklabel: no disk label
nfs_open: must mount first.
open netbsd.vax: No such file or directory
> boot netbsd
getdisklabel: no disk label
nfs_open: must mount first.
3562328+185800 [249840+236211]=0x409fd4
é
?04 ISP ERR
  PC= 800002BC PSL= 041F0000

>>>

NetBSD/vax 8.3 ISO:

>>> boot dka400

-DKA400
>> NetBSD/vax boot [1.12 (Sat May 4 18:57:00 UTC 2024)] <<
>> Press any key to abort autoboot 0
getdisklabel: no disk label
nfs_open: must mount first.
open netbsd.vax: No such file or directory
> boot netbsd
getdisklabel: no disk label
nfs_open: must mount first.
3470932+210940 [245872+228624]=0x3f6fa8
é
?04 ISP ERR
  PC= 80287918 PSL= 041F0000

>>>

OpenBSD/vax 5.8 install ISO on the exact same hardware setup burned to the same CD-RW disc boots and works just fine.
>How-To-Repeat:
* Burn NetBSD/vax 10.1 / 9.4 / 8.3 release iso to a disc.
* Boot it on a 3100 m40 using an external SCSI CD-ROM.

>Fix: