CompuPro - CPU 8085/80
This was CompuPro's first 16 bit CPU board. By combining the 8085 with an 8088 on the one board it provided a convenient way for users to migrate from 8 bit/CP/M software to 16 bit systems even though the absence of a Z80 with its efficient special op-codes was a frustration.

The 8085 provided both hardware and software compatibility with the current crop of S-100 peripherals. The 8088 provided for greatly enhanced software capability while maintaining an 8 bit external  bus  for hardware compatibility. The user could switch back and forth between the two processors with a simple software command. For example, this allowed the user to let the 8085 run his currently available (and familiar) disk operating system while letting the 8088 run the more advanced applications software. One processor would then "call" the  other   to  handle  the   task most   suited  to  it. This environment is also extremely effective when trying to develop new software for the 8088. One could use tools available that run under the 8085 (such as CP/M and Sorcim's 8086/88 Macro Cross-Assembler that ran under CP/M) to write the new code and then simply switch over to the 8088 to try it out. PROM's did not need to be burned and erased and systems pulled apart to transfer the code to the 8088 system. The 8088 ran at 8 MHz and the 8085 at 6 MHz to maximize through­put. A switch was provided to slow the 8085 down to 2 MHz for software dependent timing  loops that want to run at  that  speed and  are not easily changed. The 8085 could of course directly address 64K bytes of memory, but the board had a  built-in Memory Manager scheme that  allowed access to the full 16 megabytes available per the IEEE 5-100 standard. The 8088 could directly address 1 megabyte, but their Memory Manager hardware was smart enough to know which processor is in control. Thus the 8088 used only the upper four bits of the Memory Manager so it too can access the 16 megabyte address space.  The CPU 8085/88 rigidly adhered to the IEEE S-100 standard, but seemed to work quite well with most well designed pre-IEEE hardware. For example, provision is made to use the IMSAI front panel even   though  it  doesn't   exactly fit into  the new standard.
 
The manual for this board can be obtained here.

 

Other CompuPro S-100 Boards
CPU8085-88  CPU86-87  CPU-Z  Disk1  Disk1A  Disk1B  Disk2  Disk3   EconoROM2708  
RAM Boards   Interfacer 3  Interfacer 4  Interfacer II  M-Drive  MPX-Board  PC-Video  
System-Support1  System-Support2   SPIO  Spectrum  SP186   CPU-286   68000   SPUZ