Radeon HD 4870 X2 preview

Both the 4850 and 4870 products utilize the same chip, make no mistake. What you'll notice is that the 4850 will run at a 625 clock frequency and comes with 512MB GDDR3 memory (framebuffer) clocked at 1986 MHz. These two factors are pretty much the biggest difference compared to the big brother 4870. Power requirements aren't bad either. You can expect a 110 Watt peak watt power consumption per GPU in this configuration.

That second configuration is obviously that sweet Radeon HD 4870. We see exactly the same GPU mounted on this board, yet there are some distinct differences to be found. The performance of this product is tweaked and maximized. You will notice that AMD's board partners will have higher clock frequencies on this product boosting out some more performance. Yet more importantly, this is the product you guys hear so many rumors about .. the product with GDDR5 memory. GDDR5 is a first for sure.

There are some distinct advantages to be found for GDDR5 memory. It's has much higher frequency based memory versus tight timings. In the end this gives the Radeon HD 4870 a performance boost as GDDR5 memory will leverage overall peak bandwidth to a theoretical (roughly) 3.6 Gbps. And that's just crazy fast (GDDR3 on 4850 = 2.0 Gbps).

This is the biggest difference between the two (4850/4870) models. Next to the memory, and I already mentioned this, you can expect higher clock frequency for the core/shader domain, 750 MHz will be the default clock frequency and memory wise ... the frequency sees 3600 MHz.

Hover with your mouse over this photo to magnify.

The product we preview today is based on the 4870, yet two GPUs merged together with a bridge chip utilizing crossfire technology to render your games faster. "What's Crossfire?" some of you might ask. A valid question as we take verbs like Crossfire & SLI for granted these days.

Well, just like NVIDIA's SLI, Crossfire is a situation where you add a second, third or even fouth similar generation graphics card (or in today's case GPU) to the one you already have in your PC and effectively try to double, triple, quadruple your raw rendering / gaming performance.

The idea is not new at all though .. if you are familiar with the hardware developments over the past years you'll remember that 3dfx had a very familiar concept with the Voodoo 2 graphics cards series. There are multiple ways to manage two cards rendering one frame, think of Supertiling, it's a popular form of rendering. Alternate frame Rendering, each card will render a frame (even/uneven) or Split Frame rendering, simply one GPU renders the upper or the lower part of the frame. So you see there are many methods where two or more GPUs can be utilized to bring you a gain in performance.

The R700 as tested today is based on a 4870 configuration. You'll spot several models on the actual launch based on multiple configurations.

Yet the engineering sample that we received is based on the 4870 as it has a core frequency of 750 MHz and the product has it's gDDR5 memory clocked at 900 MHz which quadruples itself to an effective frequency of 3600 MHz. Doubling up, also means doubling up the memory amount, which is now set at 2 GB on this card. See, each GPU will clone that memory. Example, each texture is sitting in both the framebuffers as the GPUs can not share that buffer -- cloning.

Let's compile a chart and look at the differenced:

And that R700 product we'll look at as AMD want to reveal a bit of what they are working on. Anyway, let's have a look at the product and talk some more.