AMD's Radeon HD 4000 series graphics cards are impressive on most fronts, but, they're a touch hotter than most users would like - particularly the single-slot Radeon HD 4850.
The heat-factor isn't helped by AMD's lacklustre automatic fan control. Up until now, users have been unable to manually control the speed of their fans.
That, however, is no longer the case as a forum user going by the name of bretware over at Guru3D has provided a useful workaround that'll let users manually control their card's fan speed, and consequently lower temperatures.
According to bretware, a user needs to follow these simple steps:
1. In Catalyst Control Centre, make sure clock and memory settings are correct and turn on Overdrive
2. Create a Catalyst Control Centre profile called "fanspeed"
3. Navigate to C:\Users\UserName\AppData\Local\ATI\ACE\ and you'll find an XML file titled "fanspeed", open the file in Notepad or your preferred editor. The file should resemble the following:
<Property name="FanSpeedAlgorithm" value="Manual" />
<Property name="Want" value="0" />
<Property name="Want" value="65" />
4. As shown above, change the "FanSpeedAlgorithm" value to Manual and the "FanSpeedPercentTarget" value to 65 (or your preferred fan speed in percentage)
5. Save the file and reload the "fanspeed" profile in Catalyst Control Centre.
If you're unable to locate the XML file, you may be required to set your operating system to show hidden/system files.
Bretware adds that "you may have to select the profile everytime you start the computer, but it will work until there is a fix or better info so i can figure how to change the auto target temp".
Long story short is that it works and it works very well.
I started out with the card on automatic fan speed (the factory default setting) and found it to peak at 85C... The fan is only spinning at 41% and doesn't go any faster than this.
With the fan speed manually set to 100% the temperature dropped from 85C to 61C, which is a 24C temperature drop by just making a custom profile. The fan is way too loud at 100% though, so I grabbed the decibel meter and found it to be at 77dB at 100% rotation (the fan is spinning at 8,000 RPM, which is hella fast)... Just figured I'd post this up as other Radeon HD 4850 and Radeon HD 4870 owners might be looking for a way to lower their temperatures or increase the fan speed on these Radeon cards. Having the fan set to 60-70% seems to be the sweet spot, if you are wanting a nice mix of cooling and noise.