Slide show


In the early 1980s Alpha Omega developed several industrial process control and security and alarm control applications using PDP 11-23 computers. The PDP 11s were very expensive and not reliable in some industrial situations. In 1981 we set out to build a faster, more reliable and less expensive computer for our applications.


The AO Z80 Computer was designed for the popular STD-Z80 bus. It was a dual-processor system designed for 10 MHz Z-80 CPUs. Each CPU had a memory page map to access 256 Kbytes of shared dynamic RAM. One CPU was paired with a 32-bit trigonometric or 64-bit floating point Arithmetic Processor Unit IC. The other CPU was paired with a floppy disk controller IC to create an "intelligent" disk controller that automatically configured itself to work with 8", 5¼" or 3½" floppy drives and automatically worked with single- or dual-sided and single- or double-density diskettes. Larger installations used a 5 Mbyte removable cartridge hard drive.

AO designed a variety of STD-Z80 Bus cards to operate in the computer. A 10 MHz 256 Kbyte Dynamic RAM Card supported the dual-processor configuration. A High Speed Math Coprocessor card executed 16 bit multiply and divide operations in the time between the last data write from the CPU and the first result read operation, with no wait states.


The AO STD-Z80 Bus Computer was perhaps the most avanced microprocessor system of its day. Production cost was about ¼ the PDP 11-23 price and it was a more powerful computer for computation of PID control cycles when our High Speed Math Co-processor card was installed. It was used successfully in many applications through the 1980s and early 1990s. A hardened version was used in our plywood lathe control systems, and generated most of the plywood veneer produced in North America through the mid 1990s.

STD Bus Cards