Larrys test where done on a 2012 iMac which I believe uses the
NVIDIA GeForce GTX 660M graphics processor with 512MB of GDDR5 memory
or
NVIDIA GeForce GTX 675MX graphics processor with 1GB of GDDR5 memory
Configurable to NVIDIA GeForce GTX 680MX with 2GB of GDDR5 memory.
It would be interesting to try this on a computer with an ATI graphics card.
Dajen Productions, Santa Barbara, CA
Mac Pro 3.5MHz 6-Core Late 2013
FCP X