Sapphire Radeon HD4850 512MB Graphics Card Review

Under the Heatsink

Please remember that removing the heatsink on this card will void your warranty.


Even though removing the heatsink will make short work of any warranty, the process of taking it off is extremely easy. There are a few screws securing it to the PCB and once these are loosened, it is just a matter of gently wiggling the heatsink free.


The R770 core is surrounded by a metal shim to keep it in place underneath the heatsink and unlike some recent Nvidia cards, there is no IHS to disperse the heat. Rather, the core makes direct contact to the underside of the heatsink which should help speed up heat transfer.

Surrounding the core are the eight GDDR3 modules which are used on this card. On the HD4850 ATI is using Qimonda HYB18H512321BF-10 modules which are laid out in an 8x64MB pattern and are rated to run at 1Ghz (2Ghz DDR) at 2.0V. Considering they are running at 1.986Ghz we don’t expect much in the way of overclocking on stock volts but there have already been some outstanding overclocks achieved on these cards in the short time they have been out.


Where the HD4870 used extremely robust Pulse and Vitec inductors for voltage regulation, the HD4850 needs a bit more mundane components considering the core and memory run at much lower speeds. To this end it is equipped with a quartet of larger inductors each of which is paired up with a set of smaller VRMs. Due to their small size in relation to the heat they produce, it is strongly recommended that you cover all of these components with heatsinks if you are going the aftermarket cooling route.


The underside of the HD4850 heatsink looks much like any other heatsink we have come across other than the fact that it is completely made out of copper. There are thermal pads for the eight ram modules as well as the VRMs closer to the back of the card but there is one thing that really sticks out for us: it looks like there is a mini vapor chamber where the heatsink makes contact with the R770 core.

Regular readers among you may remember our Sapphire HD3870 512MB TOXIC Edition Review where we went into the details of what a vapor chamber is and how it performs when cooling off a graphics card. While their Toxic version had a vapor chamber which ran nearly the entire length of the heatsink, the HD4850 places a 2” x 2” chamber directly above the core. In theory, this will negatively impact the cooling potential of this technology since it really shines when the heat is spread over a wider area and can be distributed to a large number of fins placed near the fan. To be honest with you though, the only way to check if this is an actual vapor chamber is to cut the cooler in half…which we are unwilling to do.


Interestingly, the entire base of the heatsink (except directly over the core contact plate) is covered in a clear plastic that looks to be shrink-wrapped in place. The reason for this is a bit of a mystery to us.