New unified amd64-install.img does not work with some older hardware

Hi all,

I recently found that the amd64 installer image provided for 9.1_STABLE
doesn't work with some older machines I have. I see there was a pull-up
submitted to provide a single UEFI and BIOS installer to the netbsd-9
branch some time ago.[1] Of the three machines I tested, results were:

Lenovo T420: installer image apparently not recognized, it simply gets
skipped after being selected to boot from.
HP DL360 G6: the first stage bootloader string flashes on the screen,
then it gets skipped.
Lenovo x131e: works without issue.

(The older BIOS-only image from 9.0 works without issue on all three
machines.)

The simplest solution seems to me to bring back two distinct installers.
Perhaps the present one could be left as-is, and the older BIOS-only
version brought back as "amd64-install-legacy" or such. If someone has
other suggestions on how to get the unified image to work more
universally, I can help test.

Please CC me on responses, as I'm not subscribed to this list.

Regards,

Dave

1. http://releng.netbsd.org/cgi-bin/req-9.cgi?show=933