HD3870, HD3850 review - Is RV670 the new mid-class DX 10?

Page 2 - HD3800 Technical specifications

First thing we notice in the new Radeon HD3800 series is the change in naming policy for the different models. In the past adding suffix in the model name was exception, reserved only for the top model, but with time the different "GT, GTS, XT, PRO, GS, SE" and so on, became mandatory in any class of every family of cards in both leading companies. Yet now AMD, after taking surveys amongst ordinary gamers (major clients for this class of product), decided to take a different approach, by using only digits. It's easier to distinguish the faster model between HD3870 and HD3850, than for example to arrange by performance 2900PRO, 2900GT and 2900XT if you are not at least a bit skilled in the hardware sphere, now is it...

So it's time for the technical part of the review. The core, base of the HD3800 series cards is codenamed RV670. It's the natural successor of R600, so let's look at the differences. For starters the RV670 is manufactured by the 55nm process. This naturally allows fitting more transistors on smaller surface, higher working frequencies, more technologies fitted in the chip, lower voltage, which means lower power consumption. Its dimensions are 192mm2, compared to R600, which is 80nm and measures at 420mm2, thus making RV670 the "slimmest" video chip so far (G92, the base for the new 8800 cards is 65nm measuring at 330mm2). And those are all the differences. Unlike NVIDIA, which made major changes on G92, compared to his predecessor G80, AMD decided to leave the architecture almost untouched...

We are talking for the same quantity of Stream processors – 64 five-way superscalar Shader processors or 320 if you fancy naming the sum of all executing units. On the other side the internal RingBus is lowered from 1024bit to 512bit and the memory bus is 256bit or to put it simply the amount of connections is lowered in half, saving AMD of using about 100 000 transistors, which i s substantial number when we look at the big picture. The ROPS and the memory channels retain their numbers, we're just using 8 x 32bit, instead of 8 x 64bit. Of course RV670 supports CrossFireX technology. Meaning CrossFire modes with 2, 3 or 4 video cards, as long as you motherboard has enough slots. Contrary to AMD's move, NVIDIA decided to keep the new 3-way SLI only for the older G80 cards, so the new GeForce G92 8800's have only one connector for SLI bridge, allowing a maximum of 2 cards in SLI mode.

New is the support of DirectX 10.1 and Shader Model 4.1, compared to DirectX 10 and SM4 in R600, yet even though AMD claims that this could produce better picture, it is highly unlikely that you will notice it. Still those "improvements" give a marketing bonus to HD3800, in spite that only with the release of Service Pack 1 for Vista (expected at some point of the first half of the year), Vista will acquire support for Shader Model 4.1 and DirectX 10.1, which at least on paper gives more potential for better lighting effects and details in the games that have the engine capable of representing them.

AMD' marketing experts also accentuate on the new “PowerPlay” power saving technology of the new RV670 core. PowerPlay is the graphics representation of “Cool'n'Quiet”. Meaning that when the chip is used in 2D mode or in low intensity 3D, much of its 3D processing parts are shut down, thus not only lowering the temperature but also lowering few times the power consumption.

On the next page we'll be viewing the differences between the models on the HD3800 series.