The H316 is basically a re-engineered DDP-516. Most of the logic design is identical, and it is entirely binary compatible with the DDP-516. By using more highly integrated chips, and later generation core memory, it was possible to reduce the size from something the size and weight of a small car to something that fits under a desk and can (just) be lifted by one person.
The H316 has a longer cycle time (1.6 microseconds) than the DDP-516.
Find a home for this The first Series 16 machine I used was a DDP-516, and I now own an H316 (some notes on these machines).