Review: Two RV670 vs. 8800 Ultra
The new dual-chip R680 card is finally here, and it is known as Radeon HD 3870 X2. This card managed to bring ATI back to the top, where Nvidia has been lonely for a long time. A Radeon card can finally once again compete with Nvidia's high-end cards such as Geforce 8800 Ultra and 8800 GTX.
With this twin-chip on one board card running in Crossfire mode, ATI’s future finally looks bright. Priced at €400+, even its price points are an instant success; especially knowing that Nvidia’s Ultra cards aren’t this affordable.
At first glance, this card appears quite large, but Radeon HD 3870 X2 isn’t any larger than Ultra, and although it packs two RV670 graphics chips the power consumption stays at acceptable levels. Although there is talk of 200W consumption, our actual testing resulted in our complete system using 377W under workload. The same Core 2 Duo 6800 Extreme setup, but with Nvidia’s Ultra card, resulted in consumption of 359W. Thanks to PowerPlay technology, our Radeon HD 3870 X2 system used only 195W in idle mode, while the Geforce Ultra card in idle mode needed 227W.
One 8-pin and one 6-pin power connectors are powering the card, just like 2900 XT. The cooler even resembles the cooler seen on 2900 XT, but this time it has no heatpipe and is slightly longer because it cools two graphics chips. The fan has undergone some serious improvement and it stays quiet until the card is put through its paces at highest workloads, whereas visually it still resembles the cooler seen on 2900 XT.
Our system recognized it as just another piece of hardware so the card will run at any PCI Express x16 slot. This means that we finally have some type of CrossFire that will run on Nvidia’s chipsets. Radeon HD 3870 X2 has all the characteristics of an HD 3870 card – DirectX 10.1, Shader Model 4.1, OpenGL 2.0, PCIe 1.1 and as for other features, it’s the same times two: 2x320 Stream processors, 2x16 ROP’s, 2X512MB of memory, 2x55nm RV670, etc. The chip features PCIe 2.0 interface, but the onboard bridge chip PEX 8547 only supports PCIe 1.1, so you will lose all the benefits of PCIe 2.0.
The back of the card houses a passive block that goes the whole length of the card, and since it packs the cooler screw-holders, its primary use is to keep the cooler in place. Its job is also to cool the memory blocks on the back of the card, and it makes sense since the modules are in direct contact with the tin block. Looking at the card from the front will not shed light on where exactly the two RV670 cores are, but a quick glance at the back certainly will.
The cores are each surrounded by 4 Samsung memory modules, because ATI couldn’t fit everything on the front.
HD 3870 X2 packs 1GB of memory, 512MB per core. Memory interface is 256-bit, but the internal ring bus memory controller is 512-bit.
Our sample we reviewed runs at reference 825MHz core and 900MHz for Samsung GDDR3 memory. ATI managed to push this card over 800MHz, but we’ve already seen that partners will overclock these cards to 850MHz+.
Although we knew that both coolers aren’t made of copper, we still took them apart and checked. A card with two copper blocks would simply be too heavy for a PCIe slot, so ATI didn’t want to risk cracking the motherboard.
Using an aluminum block rids the card of excess weight, while still managing to efficiently cool the card. Next to the fan you’ll find an aluminum block that cools faster than copper, but it also heats up more slowly, meaning that transferring heat between the core and aluminum takes longer. The decision to do this was probably made after testing in the air-tunnel, or maybe because the I/O part of the card, next to the heavy copper block, is screwed to the case, whereas the back part of the card leaning on the PCIe slot is only carrying the weight of aluminum.
Between RV670 cores, you’ll find a PCIe Bridge Chip (PLX) whose job is internal chip communication on the R680.
Bridge chip is also cooled but it only touches the cooler base, without having a separate copper or aluminum block.
You can hook your Radeon HD 3870 X2 in CrossFire, but another CrossFire connector on the card means at least another card. CrossFire drivers aren’t ready yet, but they will make connecting another HD 3870 X2 possible, which will result in 4 RV670 chips in quad CrossFire. The same goes for 4 single HD 3870 or HD 3850 cards.
Due to the spacing in the case, those who want quad CrossFire will probably opt for two dual-chip cards, unless they want more monitors. We’re not yet sure whether tri CrossFire will work with HD 3870 + HD 3870 X2.
HD 3870 X2 has two DVI outs, but two more are possible because as we’ve said before – HD 3870 X2 packs, as its name suggestively states, everything that HD 3870 offers, times two. Asus already has a card with four DVI outs and dual-fan cooling, and that is an indicator that partners will definitely go wild with these. MSI didn’t alter the reference design, but they did overclock the core to 850+MHz.