My friend had issues with the Ati 4850 locking up on guildwars (running at max settings)
Turned out to be heat related. His card was hitting 84C..... (no over clocking of the card either)
He replaced the heatsink with 3rd party cooler and now it works perfect, and about 41C (highest).
With the newer drivers, it will tell you the gpu temp, so if it's locking up, you may want to take a look at that.
Ati 4850 Issue - One possible fix.
EternalTempest
moriz
the HD4800 series temperature issue is well documented, and there are a number of easy fixes that doesn't require 3rd party coolers.
one is to edit an overclocking profile to manually set the fanspeed to 40%+ (no actual overclocking required).
the other is to flash the bios so the fan spins up. i took this approach, and the card rarely goes above 65C.
one is to edit an overclocking profile to manually set the fanspeed to 40%+ (no actual overclocking required).
the other is to flash the bios so the fan spins up. i took this approach, and the card rarely goes above 65C.
Elder III
I have that card on my new pc and I have noticed that it runs a little hot, but I have 2 extra coolers in there to take care of it. 
As Moriz said, it is effective to flash the bios also - it worked on my end anyways.
As Moriz said, it is effective to flash the bios also - it worked on my end anyways.
Raku Clayman
I installed a Sapphire Radeon HD 4850, yesterday. It's a great card. The first thing I did was to try it out in GW with all the settings maxed. It ran effortlessly, although I noticed the temp was around 75-80 deg C. I checked around and found the fix to increase fan speed. Here is the link to that easy fix: http://techreport.com/forums/viewtopic.php?f=3&t=60232
I increased the fan speed to 50% from 24%. It now records a temperature of 49 deg. I chose 50% because I read that it remained relatively noiseless if the fan speed stayed under 50%, which I prefer.
I have a Zalman VF900 cooler that I was about to put on it, but, I will run it this way for a while. I have used Zalman coolers for a number of years and I really like them. I mention this because the Sapphire HD 4850 Toxic comes with a Zalman cooler already on the card. I paid $154(price after $15 rebate), with free shipping. The Toxic currently is $199 with a $20 rebate, so, $179. The Zalman cooler is around $38, so, if you are thinking of buying the card and a cooler, the Toxic is a really good deal and you don't have to install the cooler yourself.
I increased the fan speed to 50% from 24%. It now records a temperature of 49 deg. I chose 50% because I read that it remained relatively noiseless if the fan speed stayed under 50%, which I prefer.
I have a Zalman VF900 cooler that I was about to put on it, but, I will run it this way for a while. I have used Zalman coolers for a number of years and I really like them. I mention this because the Sapphire HD 4850 Toxic comes with a Zalman cooler already on the card. I paid $154(price after $15 rebate), with free shipping. The Toxic currently is $199 with a $20 rebate, so, $179. The Zalman cooler is around $38, so, if you are thinking of buying the card and a cooler, the Toxic is a really good deal and you don't have to install the cooler yourself.