Page 2 - Specifications, Technology & Bundled items

Behold and be taught about R680

RV670 is the codename for the chip embedded on the Radeon HD 3850 & 3870 graphics cards. The 3870 X2 utilizes two of these chips, which were relabeled as the R680. To gain some understanding, we first need to explain the architecture a little.

On to the dirty tech talk; the RV670 graphics core by all means is not just a die-shrink of R600 (Radeon 2900 XT). It does fix a lot of inefficiency issues that ATI faced with R600 (Radeon HD 2900 XT). The processor is now manufactured at a much smaller 55nm process and entails a significant number of improvements. Let's walk through the more important ones.

For me personally, there where two very big improvements on the 38xx series of GPU. You'll get near same performance as a HD 2900 XT at half the price and secondly, half the power consumption (thus lower wattage). Do you guys remember that the 2900 cards had two power connectors (one 75W 6-pin & one 150W 8-pin) ? That's completely obsolete. Just a 6-pin connector will be sufficient as the fastest model announced today (HD 3870) uses merely half the Wattage of that 2900 XT at roughly 105 Watt (peak).

There are a number of reasons for the decrease in power consumption. Obviously the 55nm fabrication process is showing it's advantages there as the smaller a die size is the less voltage it requires.

Let me try to explain this in a very laymen explanation:

Think of soccer/football. Flood a football field with water. And instead of kicking the ball we use the water flow to get the ball from point A to B. Now we cut that football field in half yet have the same amount of players playing soccer, this would mean we'd use less water. And the soccer players would get their football quicker from point A to B as the distance is shorter. In the case of this silicon, the soccer field is the RV670, water would be the current flowing through the silicon. The soccer players the transistors and the football the data transmitted.

Next to that smaller die-size, AMD also incorporated ATI Powerplay (known from their mobile products) into the GPU which seems to do wonders in power consumption as it can regulate voltage levels and clock speeds on the fly. Pretty brilliant, we'll show you some results later on.

Next to shrinking that die-size, ATI did make another clever move; the move back to the 256-bit memory bus (still using the 512-bit ring-bus). It's much cheaper to work with memory and less expensive to integrate. So combining these factors can make the overall products less expensive. RV670 and thus R680 as well also makes the move towards PCI-Express 2.0 compatibility which doubles the bus (PCIe) data rate towards 16GB/s. Not that we need it at this time though ... although with CrossfireX it might make a difference.

	ATI Radeon HD 2900 ATI Radeon HD 3850 PowerColor Radeon 3870 X2 ATI Radeon HD 3870 # of transitors 700 million 666 million 1332 million 666 million Stream Processing Units 320 320 640 320 Clock speed 742 MHz 670 MHz 825 MHz 775 MHz Memory Clock 1.6 GHz (effective) 1.66 GHz (effective) 1.8 GHz (effective) 2.25 GHz (effective) Texture Units 16 16 32 16 Render back-ends 16 16 21 16 Memory 512MB GDDR3 512MB GDDR3 2x 512MB GDDR3 512MB GDDR3/4 Memory interface 512-bit 256-bit 256-bit 256-bit Fabrication process 80nm 55nm 55nm 55nm Power Consumption (peak) ~215W ~90W ~200W ~105W

PowerColor Radeon HD 3870 X2 with 1 GB memory

The product as tested today comes from our acquaintances at TUL, which is the company behind PowerColor, the product as tested today is 100% reference; keep that in mind.

For the record again; RV670 and R680 what is the difference. See if you take two RV670 graphics processor units, stick them on the same PCB and bridge them .. then you have a product under codename R680. R680 is simply a codename that ATI used to develop this multi-core based graphics card. So if you'd take two 512 MB HD 3870 cards and run them in Crossfire ... you'd have nearly identical performance. And I do say nearly as there certainly are a couple of differences.

There's more to the Radeon HD 3870 X2 rather than merging two GPUs on one board, bridging them (see that as an internal x16 PCIe bus connection for data communication); no they changed another thing or two.

See, not only is the effect of two GPU's rather surprising, so is the clock speed; while gaming the card will clock itself upwards towards an amazing 825 MHz (which is 775 MHz on a reference Radeon HD 3870). The memory however is clocked at 1.8GHz, which is frivolously slower compared to the fastest 2.25 GHz reference 3870, yet still plenty of bandwidth and more cost effective. And then the really special feature; you can combine two Radeon HD 3870 X2 cards and activate them in CorssfireX mode.

What's Crossfire ? Some of you might ask. A valid question as we take verbs like Crossfire & SLI for granted these days.

Just like NVIDIA's SLI, Crossfire is a situation where you add a second similar generation graphics card (or in today's case GPU) to the one you already have in your PC and effectively try to double your raw rendering / gaming performance. The idea is not new at all though .. if you are familiar with the hardware developments over the past couple of 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 Radeon 3870 X2 is utilizing this technology to produce it's rendering performance. A more interesting fact is that AMD-ATI is working on a CrossFireX driver (1st official version to be released in March) where you can physically combine two Radeon HD 3870 X2 cards and thus have a 4-GPU rendering platform. That's a lot of shader power guys !

Right, let's have a peek at what PowerColor offers with in the packaging. PowerColor bundled the card with the following:

Thou shall find:

• PowerColor Radeon 3870 X2 1GB (x1)
• DVI to VGA Dongle (x1)
• DVI to HDMI Dongle (x1)
• S-Video to Composite adapter (x1)
• Crossfire bridge (x1)
• 6-pin to Molex power adapter cable (x1)
• Manual
• Driver CD

Yes indeed a Crossfire bridge connector is included as well, very much needed as will be possible to combine two HD 3870 X2 cards in CrossfireX. Four graphics processors crunching games for you. A pretty interesting concept which we'll look deeply into in March.

Anyway, the bundle is a little average. No additional software in the form of full games though it's sufficient to get is hooked up and started.