With the very light workload of idling and video playback, the graphics cards when using the Radeon driver already tended to be warmer than the Catalyst driver, which properly supports PowerPlay and other power management technologies by default. The open-source power management options must be toggled manually and even then the mileage may vary. Some of these graphics cards were easily 8~10+ Celsius warmer when using the open-source driver! The Radeon HD 5830 was more than 20C warmer with the open-source driver. (The temperature in my office during all of this testing was maintained at about 23.3C.