Originally Posted by shattered
De-skeletonized uknc.cpp shows signs of life:

[Linked Image from img-fotki.yandex.ru]

This machine was standard equipment in many computer classes in high schools, so there's plenty of educational software and games. There are two existing emulators, one of those is open-source (https://github.com/nzeemin/ukncbtl).

Working on a forward port of this code; one weird trick this hardware does is a byte-wide hookup of a 8255 to 16-bit bus without using byte-wide instructions, not sure how to handle that in MAME.

8255 is mapped at 177100-177103 and the code goes like this (https://raw.githubusercontent.com/shattered/retro-bios/master/ms0511-uknc/ROM5.lst):
136004$:MOV	R5,-(SP)
	MOV	#174,177103$
	MOV	#200,177102$
	JMP	136056$

and so mem_mask in write handler is 0xffff in both cases:

[:subchan] ':subcpu' (136016) W 177102 <- 000174 & 177777
[:subchan] ':subcpu' (136024) W 177102 <- 000200 & 177777