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HD 3870 X2 puts up a fight

by on28 January 2008

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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.

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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.

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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.

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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.

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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.

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The cores are each surrounded by 4 Samsung memory modules, because ATI couldn’t fit everything on the front.

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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+.

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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.

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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.

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Between RV670 cores, you’ll find a PCIe Bridge Chip (PLX) whose job is internal chip communication on the R680.

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Bridge chip is also cooled but it only touches the cooler base, without having a separate copper or aluminum block.

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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.

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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.

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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.



 

Benchmarking

 

Testbed:

Motherboard:
EVGA 680i SLI (Supplied by EVGA)

Processor:
Intel Core 2 Duo 6800 Extreme edition (Supplied by Intel)

Memory:

OCZ FlexXLC PC2 9200 5-5-5-18  (Supplied by OCZ)
        during testing CL5-5-5-15-CR2T 1066MHz at 2.2V

PSU:
OCZ Silencer 750 Quad Black (Supplied by OCZ)

Hard disk:
Seagate Barracuda 7200.9 80GB SATA (Supplied by Seagate)

 

CPU-Cooler:
Freezer 7 Pro (Supplied by Artic Cooling)
 

Case Fans:
Artic Cooling - Artic Fan 12 PWM
Artic Cooling - Artic Fan 8 PWM

ATI Driver:

Sample-R680_xp_vista_8-451-2-080108a
8-1_xp32_dd_ccc_wdm_enu_57717

Nvidia Driver:

169.21_forceware_winxp_32bit_english_whql
169.28_forceware_winxp_32bit_english_beta

 


Futuremarks

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All 3DMarks report ATI HD 3870 X3 to be the fastest. If it only worked that way in the real world, owning this card would be like winning the lottery.


Gaming

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HD 3870 X2 did well in comparison to Geforce 8800 Ultra, and the cards were quite even. Compared to a single HD 3870 card, the new dual chip card succeeds where HD 3870 fails, and it’s antialiasing. With antialialiasing on, a single HD 3870 is about 50% slower than its twin brother, whereas when you turn antialiasing on, it’s slower by 32%.

 

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ATI’s R680 does a great job and it outperforms Geforce 8800 GTC, but Ultra still takes the cake at higher resolutions and antialiasing on. We again see that antialiasing is ATI’s weak-spot. HD 3870 X@ outperforms a single-chip card by 54% at 1600x1200 AA, and by 66% at 1920x1440 AA. With antialiasing off, this difference drops to only 9%.

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In F.E.A.R., ATI runs over Nvidia. Even a single HD 3870 card almost reaches 8800 GTS territory. We won’t experience such a high Radeon 3870 X2 performance in every game, but the result shows that ATI still has much to offer. Maybe the new drivers push Radeon harder in the rest of the games. In this test, HD 3870 X2 outperforms Ultra by up to 23%.

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Something went wrong in Crysis, as HD 3870 X2 won’t run with Antialiasing on. It looks as if the two RV670 chips don’t communicate well. It seems as if it’s just a single chip that actually works because the result is identical to the one that a single HD 3870 got. With antialiasing off the card ran better, and at 1600x1200 the result is identical to the one scored by Geforce 8800 Ultra.

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In the famous ATI game (Half Life Episode Two), the new Radeon HD 3870 X2 beats 8800 GTX, but not 8800 Ultra. Still, CrossFire runs well and we see a good result in comparison to a single card.


Conclusion

We are witnessing an important event where DAAMIT has finally awakened and put up a fight. The HD 3870 X2 card with two RV670 graphics chip is likely to be a hit, and it will be interesting to see what antidote Nvidia has in store.

Dual chip cards are likely to have driver problems at least for a while, but the performance increase in comparison to one card is apparent, so you can count on 60% to 70% more power.

It seems that this is the path ATI wants to take in the future, and this ultra "hot" card is faster than Nvidia’s 8800 Ultra, but only by a few percent. At the time of writing this review, ATI finished a new driver that should increase performance in Crysis, but only in Vista. Still, we’re confident that ATI will keep polishing and improving their drivers.

This is a big step forward and priced at €400, it is most definitely gives a great bang for the buck.

Last modified on 29 January 2008
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