BTW, I've updated my Venix github thing with (a) a copy of all the VENIX manuals from bitkeeper's (thanks for the pointer). They cover both PRO and Rainbow version of VENIX! And they cover the missing system calls I'd worried about. and (b) I've started a write up for how to install on MAME.... It's still super incomplete. I need to rebuild MAME with the fixes to the boot roms, at the very least since it's not (yet) working...