We've been reporting on a power bug of sorts with Nvidia graphics cards for quite some time now. The issue rears its ugly head whenever high-refresh-rate monitors are connected to GeForce cards in certain configurations. At first, the problem showed up with a single high-refresh-rate display connected. Nvidia fixed that clock speed surging with version 361.43 of its drivers, but the behavior didn't go away for folks with multiple high-refresh-rate monitors. A reader tipped us off to that problem in March, and we confirmed it independently on one of our test rigs. We later verified that Pascal cards still exhibited the issue, as well.
With the release of GeForce driver version 372.54, however, us folks with multiple high-resolution displays can enjoy the same relief as our single-monitor brethren. One of the new-feature bullet points for this driver release says that Nvidia "enabled mclk switches on 144 Hz G-SYNC monitors in multi-monitor use cases in order to lower power consumption." While that description is a bit cryptic, the net effect is that GeForce cards now run at the low idle speeds we'd expect with multiple high-refresh-rate displays connected. I've tested this new driver on my multiple-monitor main system, and I can confirm it works as expected. Kudos to Nvidia for getting to the bottom of this issue.