ATI Radeon HD 4870 X2 2GB GDDR5 - Two Heads are Better than One

The Sapphire Radeon HD 4870 X2 2GB GDDR5

The Sapphire Radeon HD 4870 X2 2GB GDDR5

As we've mentioned, the new Radeon HD 4870 X2 is, in essence, two Radeon HD 4870 cores (RV770) on a single PCB. What you get then, is close to 2 billion transistors, 1,600 stream processors, all of which adds up to give you over 2.4 teraFLOPs of computing power. And although the GPU core and memory are still clocked at 750MHz and 3.6GHz respectively, you do get up to 2GB worth of fantastically fast GDDR5 memory, making the 4870 X2 the first 2GB consumer graphics card. Add this all up, and what you have is not so much a graphics card, but a miniature super computer.

It's finally in our labs, the ATI Radeon HD 4870 X2. Our reference card looks very understated, with no hint that it is ATI's highest-end offering.

To further ensure that the new Radeon HD 4870 X2 provides top performance, ATI has also improved upon the first generation PCIe PLX bridge chip that was used in the older HD 3870 X2. Previously, the total interconnect bandwidth in the 3870 X2 was limited to 6.8GB/s. In the new 4870 X2, however, the incorporation of a newer PCIe 2.0 PLX bridge chip has increased the total interconnect bandwidth to 21.8GB/s - a three-fold increase. Not that we found the old card had any limitations in real usage, but the Radeon HD 4870 X2 nevertheless improved upon this aspect.

Our reference card from Sapphire looks very understated and as you would expect, the 4870 X2 is hefty, substantially heavier than the standard 4870. However, like the standard 4870, it uses a larger dual slot cooler, which, we are happy to report, runs rather quietly, with nary a hint of fan spin. Where it does disappoint, however, is the operating temperatures. The 4870 X2 is easily one of the hottest cards we've ever tested.

Placing the new 4870 X2 beside the standard 4870, one can see just how much larger the new dual-GPU card is.

The Radeon HD 4870 X2 is a power-hungry beast, and it shows. It requires a 6 and 8-pin power connector and a decent PSU of at least 600W power rating.

The rear I/O ports on the HD 4870 X2 is similar to those found on a standard 4870: a pair of HDCP compliant DVI outputs and a mini-DIN. Like the standard 4870, there's also an exhaust vent for the warm air to escape straight out of the system.

A CrossFire gold finger interface is provided, meaning that two Radeon HD 4870 X2 cards can be linked. Quad-CrossFire anyone?

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