The Chase Research PS4+, PS8 and PS16 were terminal concentrators that allowed the connection of 4, 8 or 16 RS232 terminals to an IBM computer using the MCA bus.
The MCA (micro-channel architecture) bus came about through IBM’s realisation that they had effectively lost control of the “standard” PC architecture. In many ways it was the heart of the PS/2 system and hence the hardware analogue of OS/2, its attempt to regain leadership (and ownership) of PC software. Arguably, it encountered just as much success (or lack thereof) as OS/2 itself.
This of course is all with the benefit of hindsight and at the time it would be a brave organisation who would bet against the might of IBM so the decision was made to create MCA versions of the Chase Research AT family, hence the PS4+/PS8/PS16.
At the moment the only documentation I have is the promotional flyer: