Since nobody seemed to answer this...

> DECstation 5000 Model 20(-50) Series Hardware Operator's Guide
> may indicate the right monitor. (As for the Model 100 Series
> http://anna.anatomie.uni-freiburg.de/~gamel/pmax/appr_monitor_dat.html)
The official answer will be in the functional specification, on DEC's
FTP server in PostScript format. I don't know.

> Furtheron: Does a PMAGB-BA/BB in the turbo channel interfere with
> the integral framebuffer?
No, it won't. Unlike on i386 where video cards are hard-wired to
particular IO addresses, both the PROM and NetBSD understand multiple
display adapters.

Andy.