ATI Radeon HD 3870 X2 Video Card ReviewMon, Jan 28, 2008 - 8:00 AM
A Closer Look At The Radeon HD 3870 X2
With the cooler removed from the Radeon HD 3870 X2, we noticed something seemed a bit off. Can you tell what caught our attention? The heat sinks that are used to cool the two cores are different. One is copper and the other is made of aluminum. Legit Reviews contacted ATI about this discrepancy and was told that both weight and cost was the reason behind the two different heat sinks. It’s obvious that a move like this will leave the door wide open to improvements in cooling, so don’t be surprised when new cooling solutions come out for this massive card.
The ATI Radeon HD 3870 X2 is not a PCI Express 2.0 graphics card because ATI used a PCI Express 1.1 bridge chip by PLX, which is located at the center of the board. Since both cores are routed to the ExpressLane PEX 8547 before the motherboard the card is limited to just PCI Express 1.1, which isn’t a big deal and actually made the card come to market faster and cheaper. The higher core and memory clock frequencies should more than make up for the ‘downgrade’ to PCI Express 1.1.
The above slide from ATI has a graphic of how data flows between the two GPUs for those that are visual learners.
The ExpressLane PEX 8547 device offers 48 PCI Express lanes and is capable of configuring up to 3 flexible ports. Since it was hard to make out in the previous picture a close-up is provided above. In case you are wondering PLX Technology does make PCI Express 2.0 PCI Express Switches and ExpressLane PEX 8648 offers 48 PCI Express 2.0 lanes, but has a different package size. This means that ATI can’t switch to this new switch easily as the printed circuit board would need to be re-done.
The ATI Radeon HD 3870 X2 is designed to use either GDDR3 or GDDR4 memory IC’s. Our test sample was equipped with Samsung K4J52324QE-BJ1A0 GDDR3 memory IC’s. The Samsung IC’s have a density of 512M bit and are rated at 1.0ns (1000MHz). Since ATI is running these IC’s at 1000MHz, don’t expect too much from them when overclocking as they are already operating at their rated speeds. Each core has eight of these GDDR3 IC’s for a total of 512MB of memory, which adds up to the entire card having 1GB.
The back of the ATI Radeon HD 3870 X2 is pretty boring, but shows the other half of the memory IC’s that are not located on the front of the card.