Thanks to Colin Wood and Allen Briggs who responded to my pleas for help
yesterday. Apparently, as I was troubleshooting the Ethernet card
yesterday, I installed System 6.0.8 thus disabling 32 bit memory mode.

After getting the messages from Colin and Allen, I simply reenabled the
Mode 32 memory addressing in the Memory control panel and I now have a
bootable NetBSD 1,1 system running on a IIsi (5/80) with a Daystar
PowerCache (50Mhz).

As for min memory requirements, Allen wrote :

Currently, I think 4MB or maybe 5 is the minimum.  I'd like to reduce
that, but that's a low priority.  ~8MB should be quite usable, although
if you're running compiles/emacs/X, you'll probably want more like 16.

Thanks one and all for all your help.

Regards,
Frank.