ATI's Digital Audio driver reduces Radeon's 3D performance?

UPDATE June 22, 2009 15:35 GMT - We spoke with key personel at AMD over this situation and the answer we got from AMD was the following: The probability for this to happen is around 2.3%. Long story short, if there is a "performance shortfall" detected on the system, that is caused by the presence of eventual 3rd party audio driver such as ones made by RealTek. The solution is simple:

• Uninstall Audio driver for the on-board sound chip
• Reinstall Catalyst drivers
• Reinstall Audio diver for the on-board sound chip

That's it.

ORIGINAL STORY

We all know that ATI was the first company to implement HDMI support with a digital HD sound hardware built-in inside the GPUs ever since X1300 and its agreement with Creative Labs [but X1K was found not to support HDCP, hence the recent class action settlement].

Radeon HD 2000 series fixed the HDCP issue and things went back to normal, but now Hardware-Infos claim that you actually lose a little bit of 3D performance if you drive the audio through the graphics card. While in theory this should not happen - as HD audio is just passing through the PCI express bus and being synced with the picture, independent testing is now showing that Radeon 4800 series suffers from a small performance drop regardless of HDMI being an active connection or not.

Benjamin discovered that disabling the "ATI Function Driver for High Definition Audio" in Device Manager brings a small performance boost.

In games such as Crysis Warhead, Far Cry 2, GRAW 2, GTA IV, Tom Clancy HAWX and Stalker: Clear Sky in 1920x1200, with 4x AntiAliasing and 16x Anisotropic Filtering, disabling the "ATI Function Driver for High Definition Audio" brought anywhere between two and five percent. Most of applications saw a difference between 2-3 percent [inside the margin of error], but five percent is a tangible difference.