Pressure cookers will almost halve the time necessary to make a good broth/stock. Also, the smaller you can break the bones (or any added vegetables), the greater the surface area will be and so the stock will form more quickly.
And as usual with stocks, you never want it to reach a boil (the bubbling clouds the stock), so let your pressure cooker cool down before you vent/open it.
Depending on whether you want a white stock or a brown stock, you can roast the meat/bones first (for a brown stock).
"Thanks to the combination of meat, calcium-rich leaf foods, and a vigorous life, the early hunter-gatherers were robust, with strong skeletons, jaws, and teeth." - Harold McGee, On Food And Cooking: The Science and Lore of the Kitchen