M164 6-Bit Parallel Adder

Summary The M164 is a high-speed 6-bit conditional sum adder module designed for the PDP-15 central processor. By calculating two simultaneous sums—one with a carry inserted (CA) and one without (NCA)—and using combinational logic to select the correct output, the module avoids the time-consuming process of propagating a carry from one adder to the next. Three of these modules function in tandem to create an 18-bit adder capable of generating a sum in 82 ns. The document also details the module's unbuffered input requirements, specific pinout configurations for inputs and outputs, TTL loading/driving characteristics, and power consumption (5V at 118 mA maximum).