FP11-E Floating Point Processor

The FP11-E Floating Point Processor is the optional hardware floating point unit for the KD11-K CPU of the PDP-11/60. The KD11-K provided the full FP11 floating point using microcode; the FP11-E was an option which provided considerably improved floating point performance.

It was a 4 hex board co-processor:

• Next Micro-Address (M7878)
• Exponent (M7879)
• Multiplier Network (M7880)
• Floating ALU (M7881)

which mounted in slots 8-11 of the CPU backplane. The main CPU can detect the presence of the FP11-E, and, if present, uses it to perform any floating point instructions found in the program.

Electrically, it connected directly to the CPU and is controlled bu it; unidirectional data buses are provided to move information (including instructions) from the CPU to the FPP, and vice versa.

The FP11-E has its own microcode, 88 bits wide, to control its operation, and interaction with the main CPU.