NorthStar - Z80 CPU Board
This was NorthStar's core CPU card for their Horizon System. It may have been used in the Advantage as well.

The board had an onboard 2708 EPROM with the Horizon monitor and the ability to auto jump to this location at power on or reset. The auto jump feature could be set for any 1K boundary within the 64K and the PROM could be located at any 1K hex location. Interrupts could be recognized, latched and pritorized by onboard circuitry. One wait state could be added for slow RAM and I/O.

An interesting note is that this board was exactly copied/sub-licensed by a German company Salota which sold S-100 boards (and others) in Europe in the early 1980's.
 
The manual for this board can be obtained here.