Rokinon 85mm f/1.4 focus confirm chip?

I'm looking to purchase a Rokinon 85mm f/1.4 aspherical lens for use on my D300. The lens is offered with or without a focus confirm chip. My question is, does anyone know specifically what this chip does? I know even with my ancient 50mm f/1.8 E Series Nikon lens my D300 can confirm focus. Does this chip for the Rokinon allow for that on the D300? Or does it only help to aid the camera's auto-exposure function (shutter/aperture priority modes)? I'm hoping my D300 is advanced enough to confirm focus without the chip, which I would assume is geared towards entry level cameras. Still, I'm not sure.

Any help?

Added (1). Thanks ace. Actually, the difference is about $40- I probably will end up going with the chip-inclusive version. But do you think the D300 will be able to confirm focus (green dot in bottom corner of viewfinder) without the chip? If so, I'd just as soon get it without the chip…

The focus "confirm chip" is probably important when you use the electronic rangefinder in your camera.

What is the difference in cost? $50

As I read the information on the website, the automatic chip is for controlling the lens aperture from the camera. My guess is that the other lens would require you to use the "stop-down" method to meter with the lens.

I would spend the extra $50 and be done with it.