INTEL GPU driver in HEAD - what is the state of Intel RC6 support

[user10508 at gmail.com]

I've posted about battery life and thermal problems on an asus k53e
sandybridge laptop running pcbsd-9-20120505 with intel kms.

I recently installed linux mint 13, mate desktop, on another partition,
because the release notes for this Ubuntu derivative distribution
mentioned that this release supported intel-RC6 at the "deepest" level.
This was for Linux kernel 3.2 and Intel X driver 2.17.x. 

Enabling Intel-RC6 at this level makes an enormous difference in
extending battery life and restoring nominal thermal characteristics.

Without this, on the PCBSD9-20120505 snapshot, battery life is cut in
half - at best - and the thermal envelope is so far removed from nominal
that I would expect reduced CPU life as a result; fans always on,
system is hot to the touch.

With RC-6 enabled on lnux mint 13, battery life is about the same as
when using win7, also installed on this laptop; about 5 hours+. 

CPU temperature varies between 39 C and 43 C; the system is cool to the
touch and the fans never run; all nominal.

In a previous post by Konstantin Belousov@, prior to the commit of
Intel GPU driver to HEAD, it was noted that enabling RC6 produced
artifacts. 

What is the state of Intel-RC6 support in the driver committed to HEAD?