A/UX 2.0: Display Card 8/24 in a Macintosh IIfx

I thought that the Display Card 8/24 supported the Two-Page Monochrome Monitor
under A/UX 2.0, provided you use 1-bit mode. But I have an installation where
this did not work. The system was a Macintosh IIfx (upgraded from a Macintosh
II). A/UX was supplied as an official released seed version of 2.0. Knowing
that there were some early beta cards that would not work, I checked the card.
It was clearly labeled "trident" and was ordered through regular channels (no
indication of being beta).

After a clean installation, the machine would freeze with a blank screen during
the startup process. It appeared to go through A/UX loading, but froze when it
was building the Macintosh side. After swapping the card and monitor with a
regular color monitor and card, things started up fine.

Can you explain?

It is not always true that the Display Card 8/24 and a Two-Page Monochrome Monitor work under A/UX 2.0 on a Macintosh IIfx set to 1-bit mode. We tested a Macintosh IIfx, running A/UX 2.0, with a Display Card 8/24 and a Two-Page Monochrome Monitor: We did a cold start (power-off, then power-on) in 1-bit mode. A/UX 2.0 didn't start up and froze during the startup process. However, if the interrupt button (on the right side of Macintosh IIfx) was pressed, A/UX continued the startup with no problems. If the Autolaunch command within the #startup shell was modified to have only the "launch" command (without the -s option, load symbol table in the kernel), A/UX 2.0 started up successfully in 1-bit mode. The Display Card 8/24 and Two-Page Monochrome Monitor seem to start up A/UX 2.0 fine on other Macintosh II machines, including the Macintosh IIx.