![[H]ardOCP](/images/blank.gif){kind=small}
- Date:
- Monday , January 28, 2008
- Author:
- Brent Justice
- Editor:
- Kyle Bennett
- Google +1
AMD's ATI Radeon HD 3870 X2
One of the more anticipated video cards of this year is finally here, AMD is launching the ATI Radeon HD 3870 X2. What will two 3870 GPUs on one board do for you in gaming? We are going to find out exactly that in Crysis, UT3, COD 4 and HL2.
Introduction
This video card is exciting for AMD and it is exciting for gamers. We are talking about the new ATI Radeon HD 3870 X2 video card that puts two R670 GPUs onto one PCB and runs them transparently in a CrossFire configuration.
Before we dive into specifications let’s go back and summarize what the Radeon HD 3870 is. The Radeon HD 3800 series was launched on November 15th, 2007, a short two months ago. In the HD 3000 series AMD launched the ATI Radeon HD 3850 and 3870. In our evaluation back in November we found both video cards to offer exceptional gaming performance for their price points. The Radeon HD 3850 was a heck of a surprise, offering the best performance under $200 we have seen yet. The Radeon HD 3870 was a huge power efficiency upgrade from the Radeon HD 2900 XT and offered solid performance in its price range.
The Radeon HD 3870 uses a 55nm manufacturing process, which allows it to achieve high clock speeds and low power utilization. It is a huge improvement over the Radeon HD 2900 XT. The Radeon HD 3870 has 320 stream processors, 16 ROPs and is clocked at 775 MHz. It has 512MB of 256-bit 2.25 GHz GDDR4 alongside with PCIe Gen2 support and DirectX 10.1 support. Go ahead and look over the specifications on this page and you can compare them with the 3870 X2 below.
ATI Radeon HD 3870 X2
What you will notice from the model name is that “3870” remains; indicating the use of the 3870 GPU but what has been added is “X2.” X2 indicates the use of two 3870 GPUs on board one PCB. So what we have are essentially two 3870 GPUs on a single board with a hardware bridge chip that allows CrossFire to be enabled at all times with both GPUs out-of-the-box. In fact, CrossFire works without any user input, just simply install the video card and benefit from CrossFire, you do not have to enable it. CrossFire is 100% transparent to the end-user, in fact there isn’t even a CrossFire tab in Catalyst Control Center. So, if you had no knowledge of this card utilizing two GPUs, you would likely never know it by using it. You would just assume it was a very powerful single GPU.
The first thing you will notice in the slide above is that the bridge chip on board is using the PCIe 1.1 protocol and not the new 2.0 (Gen2) protocol. This was done for several reasons; one being that AMD is very familiar with this particular bridge chip, so they can mass produce it in fairly short order. If they had gone with the PCIe Gen2 chip they would have had to wait for production and this card would be pushed back a few months.
Secondly there isn’t any performance advantage right now in using the PCIe Gen2 bridge chip in current games. In fact, some add-in-board partners may actually use the PCIe Gen2 bridge chip anyway in some of their SKUs. We may actually see a mix of video cards out there on the street, some with PCIe Gen2 bridge chips, and others with the PCIe 1.1 bridge chip as ATI has no plans to re-launch their own brand with the PCIe Gen2 chips. At any rate, we don’t really see this making any kind of real world performance differences yet with games.
As you can guess putting two GPUs on one PCB will require a lot of power and generate a lot of heat with possibly a lot of noise. AMD has been hard at work to reduce all of these factors with the ATI Radeon HD 3870 X2.
The total board power at full load is rated at less than 225W, which is very good considering we are dealing with two GPUs. Idle power is rated at a low 47W. AMD is using their PowerPlay technology which dynamically adjusts the clock speed and voltages of the GPUs depending on GPU activity. Only two 2x3 (6-pin) auxiliary power connectors are required, you do not need an 8-pin (2x4) connector for normal operation of this video card. If you wish to overclock though, you must connect an 8-pin connector in order to get Overdrive to show up in Catalyst Control Center.
AMD has also used aluminum and copper heatsink materials in an effort to better manage weight. Thirdly they claim this video card utilizes better airflow and is as quiet as they could make it, pulling air in from the case and exhausting it outside the back, which is the way most enthusiasts like it.
Here are the specifications in a nutshell. What you need to take note of when you look at this table is that AMD likes to double their numbers since we are dealing with two GPUs on one PCB. As we all know not everything really works out as double with a video card like this. Take for example the actual framebuffer space available to each GPU. In the case of the ATI Radeon HD 3870 X2 there is only 512MB of RAM available to each GPU, but AMD here likes to double that and say it is 1GB. There may be 1GB of RAM physically on the video card, but each GPU can only utilize 512MB of it. The memory bus is 256-bits per GPU. We may actually see some partner built cards however that do actually have 1GB framebuffer per GPU (2GB on the board total) down the road.
AMD DID however clock the GPU frequency higher over a standard 3870 video card. The GPU frequency runs at 825 MHz versus 775 MHz on a Radeon HD 3870. The memory frequency however has been reduced, and on our card as tested it was running at 1.8 GHz. Memory frequency may vary depending on which add-in-board partner you buy from. We will have to keep an eye on what memory frequencies are actually offered from partners.
One very cool feature of this video card is that CrossFireX is supported. This means that you can “CrossFire” two of these video cards for essentially Quad-GPU performance! This is something we will definitely look at when a driver is available to allow this. It should also be noted that dual-displays are supported with this single video card, so you can run with dual-displays enabled and still run all your games with CrossFire! We tested it, and it completely works as advertised.
ATI Radeon HD 3870 X2 Pictured
Here is the Radeon HD 3870 X2 in all its glory. You can see that the heatsink shroud covers the entire video card. Underneath the shroud lie copper heatsinks over each GPU and then another heatsink right atop the bridge chip. The fan pulls in air from inside the case and exhausts it completely out the back. One thing you cannot feel from these pictures is how heavy the video card is, it is not light.
Here it is in comparison to a GeForce 8800 GTX (its closest competition.) As you can see it is exactly the same length as the GeForce 8800 GTX. This is a pretty amazing feat considering there are two GPUs and a bridge chip on this one board.
On one edge lies some painted aluminum heatsinks over the RAM, as well as a CrossFire connector. On the other side you can see into the shroud and the three heatsinks sitting underneath. The first heatsink in the airstream is aluminum and the second is copper. You will also notice that the airstream is completely sealed. All the air used for cooling the 3870 X2 is going to exhausted out of the case.
On the back you can clearly see where the GPUs sit, and the bridge chip sits between them. The entire black plate you see on the back here also acts as a heatsink. The shroud makes contact with the backplane bracket; so again, there is no place for the card to exhaust into your case. Remember, only two 2x3 (6-pin) power connectors are required; you do not need the 2x4 (8-pin) connection unless you are overclocking.