PiB macOS X 64-bit Update in beta
If you're on macOS and want to test if the 64-bit version of PiB works on your system, then please try out the beta version. Here's Valve telling you how to do that:
"Right-click on the game in the Steam client and select Properties. From the Properties window, click the Betas tab."
Then select "testmac64bit" from there.
"Right-click on the game in the Steam client and select Properties. From the Properties window, click the Betas tab."
Then select "testmac64bit" from there.