Summary: With 1600 shaders, 2.0GB of GDDR5 memory, and 2.4 TeraFLOPS of graphics horsepower, the Radeon HD 4870 X2 is one impressive performer. See how the card stacks up running 8xAA against SLI GeForce GTX 280 and 260 in single card and 4-Way CrossFire. We've also thrown in 24xAA benchmarks as well. Is 2GB of memory really necessary? All the answers lie inside!
The not so secret Radeon HD 4870 X2
So what exactly is a Radeon HD 4870 X2? As its name implies, ATI merely takes two Radeon HD 4870 GPUs and slaps them on the same PCB. With two RV770 chips on one card, the 4870 X2 packs twice the punch of a conventional Radeon 4870. The card boasts 1600 shaders and 2.4 teraFLOPS of computing horsepower. Clock speeds are 100% identical to the Radeon HD 4870, but ATI spices up the package by doubling up on the memory: 1GB of 3.6GHz GDDR5 memory is devoted to each R700 chip (2GB total for the entire card) instead of the 512MB on the 4870 card we tested two months ago. Letís take a look at the boardís specs:
Officially the Radeon 4870 X2 retails for $549, but ATI has told us that they expect the board to sell for $499 very shortly. Considering that the 512MB 4870 card can often be found selling online for around $260 after rebate, we think this pricing is pretty fair for what you get. After all, the board does ship with 2GB of memory. While itís not depicted in the table above, the Radeon 4850 X2 shares the same clocks as the regular Radeon 4850 and it will sell for $399. Weíve been told that ATIís partners will ship this board with either 1GB of GDDR3 (512MB per GPU) or 2GB (1GB of memory per GPU) of GDDR3 memory. Not all of ATIís board partners will ship 4850 X2 cards however.
Why 2GB of memory?
With most graphics cards running fine with 512MB of memory, you may wonder why ATI decided to ship the 4870 X2 with 2GB of GDDR5 memory Ė thatís more RAM than many PCs!
Improving on the 3870 X2
The GPU powering the Radeon 4870 X2 is known as R700. ATI has made many improvements with this GPU in comparison to their previous R680 dual-GPU architecture found in the 3870 X2.
The final piece to the puzzle is ATIís CrossFire Sideport block. Sideport provides a dedicated link (GPU-to-GPU) combining both GPUs to each other. Thanks to the addition of Sideport, an additional bidirectional 5GB/sec of bandwidth is provided between the graphics processors. This brings the total combined bandwidth between the two GPUs to 21.8GB/sec. This is a significant improvement over the 3870 X2ís 6.8GB/sec.
However, before you get too worked up on that number, a quick reality check. While all this looks impressive on paper, keep in mind that the 3870 X2 got by just fine with its 6.8GB/sec: in our benchmarks neither the PCIe 1.1 bridge chip nor the lack of Sideport prevented it from scaling just as well as running two independent Radeon 3870 cards in CrossFire. In fact, thanks to its higher core clock and lower latency GDDR3, it scaled slightly better than two 3870 cards running CrossFire.
At first glance, the Radeon 4870 X2 board looks almost identical to the Radeon 3870 X2 card we tested back in January. The only difference that is immediately noticeable is the black PCB.
ATI uses the exact same dual-slot heatsink/fan unit that was first built for the 3870 X2, and the board continues to measure 10.5Ē. Looking closer however we can see that ATI uses larger, more powerful capacitors for the 4870 X2. This is needed because the 4870 X2 board draws up to 286W of power.
Speaking of power, as you can see the card requires one six-pin PCIe 2.0 power connector and one four-pin connector. ATI places the connectors perpendicular to the edge of the board, just above the heatsink/fan cooling unit.
This location is definitely less than ideal in our opinion, weíd prefer it if the power connectors were located parallel to the edge of the board (like the conventional Radeon 4870) as most of todayís high-end power supplies ship with bulky PCIe power cables that are fairly thick. When two 4870 X2 cards are combined for 4-Way CrossFireX, it can be a little difficult mounting the lower card as you have to bend the PCIe power cables in order for the second 4870 X2 board to fit. Most X48 and X38 motherboards just donít provide much room between the primary and secondary PCI Express graphics slots.
This can be a real bummer if youíre concerned about cooling and wish to run two Radeon HD 4870 X2 cards for 4-Way CrossFire, as thereís barely any space between the two cards. As a result, the uppermost card has a hard time drawing in fresh air, and ultimately it runs hotter. This in turn leads to the card cranking up the fanís RPMs so the GPU can remain cool. Next thing you know the 4870 X2 cards are generating over 60 decibels of noise within your system.
And what about the temps? In our testing, a single Radeon 4870 X2 ran 66 degrees Celsius at idle, and 84 degrees at load. Considering that youíre running two GPUs on one card, these temps arenít too bad in our opinion.
The beauty of a dual-GPU design like the 4870 X2 is that it gives you dual 4870 performance from a single PCIe graphics slot. You donít need a CrossFire-compliant motherboard to take advantage of this feature, any board with a PCIe graphics slot works. Once the Radeon 4870 X2 is installed within your system and the drivers are loaded, the board automatically operates in CrossFire mode.
For added performance, the card can be mated to other 4800 series graphics cards: you can combine the 4870 X2 with a regular 4850 or a 4870, in addition to a second Radeon 4870 X2. When doing this however we recommend you use a Radeon 4850 or 4870 card with 1GB of memory. If you combine a 512MB Radeon 4870 card with the 4870 X2, the R700 GPUs on the 4870 X2 will only be able to page 512MB of memory.
1GB Radeon 4850 cards are available today, and weíve been told that Radeon 4870 1GB cards will begin shipping later this month.
The Palit Radeon HD 4870 X2
The Radeon HD 4870 X2 cards we received for review today came from Palit. If you recall, Palitís really been making a name for themselves lately among NVIDIAís GeForce board partners with their custom board designs and cooling. Now Palit is taking that same approach for ATIís Radeon GPUs.
The Radeon 4870 X2 cards available at launch today are all based on ATIís reference design and cooling, but Palit has told us that theyíre working on their own custom 4870 X2 board. In addition to better cooling, the board will also feature an 8-layer PCB (versus the 6-layer board used today), dual BIOS, and better capacitors. Palit also plans to OC their board for added performance.
Right now though all the boards are being produced by the same contract manufacturer, so other than price and game bundle, you wonít find many differences between the various 4870 X2 boards. We expect youíll see the first custom 4870 X2 boards in September.
Intel Core 2 Extreme QX9770
EVGA nForce 790i Ultra SLI motherboard (for GeForce cards)
ASUS P5E3 Premium WiFi AP Edition (for Radeon cards)
4GB OCZ DDR3 @ 1333MHz
GeForce GTX 280
GeForce GTX 260
GeForce 9800 GTX+ SLI
AMD Radeon HD 4850
AMD Radeon HD 4870
AMD Radeon HD 4870 X2
Catalyst 8.8 beta
300GB Western Digital Caviar SE
Windows Vista Ultimate 64-bit w/Service Pack 1
Company of Heroes 1.71
Both ATI and NVIDIA supplied us with newer drivers for the GeForce GTX 200/9800 GTX and Radeon HD 4800 series cards than the drivers we tested with last week. In fact, ATIís Series 5 driver is so new we just received it on Monday, weíve been told it offers improved CrossFire performance over the 4850 hotfix driver that was released on Friday. Weíre also testing the Radeon 4800 cards on ASUSí P5E3 Premium X48 motherboard, whereas the 4850 was tested last week on the same motherboard as the GeForce cards, EVGAís 790i SLI.
Crysis High Ė Direct3D
This is most definitely the fastest single graphics card on the planet.
But the Radeon HD 4870 X2 is no longer going up against the GeForce GTX 280 as far as direct pricing is concerned. As a result of the latest round of GeForce price cuts, the $549 Radeon 4870 X2 is actually priced more comparably to the GeForce GTX 260 SLI setup we tested. A quick check of Newegg reveals that GeForce GTX 260 cards are currently selling for $250 and $260 after mail-in rebate. That puts a GeForce GTX 260 SLI setup at about $500-$550; approximately the same price point as a single Radeon HD 4870 X2 card.
In light of this comparison, the Radeon 4870 X2 and GeForce GTX 260 SLI run very competitive against one another, but weíre ever so slightly giving the performance edge to the Radeon 4870 X2. GeForce GTX 260 SLI performance in Lost Planet is roughly 12% faster than the 4870 X2, while Company of Heroes results varied depending on resolution (at lower res the GTX 260 ran 9-17% faster than the 4870 X2, but by 2560x1600 the pendulum swung in favor of the 4870 X2). The cards also trade blows in Call of Duty 4, with the X2 taking the early lead at 1600x1200 but by 2560x1600 it trails by 3% (of course, these tests are run with FRAPS, so you should probably consider it a tie). CrossFire scaling in Crysis isnít as polished as SLI and therefore the GeForce GTX 260 reigns supreme in this game. BioShock clearly favored the 4870 X2, with the GTX 260 SLI running about 15% slower than the 4870 X2. Our tests with older games also preferred the X2.
What really pushes the 4870 X2 over the edge in comparison to the GeForce GTX 260 SLI setup is the fact that it requires a single PCI Express graphics slot and two power connectors. You also donít need a special SLI or CrossFire motherboard.
Of course, NVIDIA would argue that PhysX is one intangible that canít be ignored. Today theyíre introducing new PhysX drivers and apps that all GeForce 8/9 and GTX 200 series card owners can check out.
PhysX is certainly a great feature, but is it compelling enough to give the GeForce GTX 260 an edge over the Radeon 4870 X2? Right now weíd say ďnoĒ, there just arenít enough quality games on the market that take advantage of PhysX, but we also must admit that weíre eager to see how games like Mirrorís Edge and Borderlands will look.
Is the Radeon 4870 X2 a better buy than picking up two Radeon HD 4870s?
In comparison to the Radeon HD 4870 CrossFire setup, the Radeon HD 4870 X2 really shined at 2560x1600 in games like BioShock, Company of Heroes, and Lost Planet. In these cases the 4870 CrossFire setup just didnít have enough memory and the 4870 X2 was able to pull away by a factor of 3-5X!! (In Company of Heroes the margin was just 27% at 2560x1600, although it also outran the 4870 CrossFire rig at 16x12 and 1920x1200 by 8-10%). If 8xAA gaming isnít a priority for you, these margins would obviously tighten up quite a bit, but considering the pricing ATI is offering on the 4870 X2 itís probably a better deal than buying two Radeon 4870 cards separately. And once again, you donít need a CrossFire motherboard if you get the X2.
So there you have it. ATIís back on top of the graphics market. The Radeon HD 4870 X2 is the best graphics card on the market right now. The only caveat that gives us a little pause however is ATIís CrossFire drivers. We hate to beat ATI up over this yet again, but last summer when the first wave of DX10 games hit shelves, ATI had an awfully tough time with their CrossFire performance. Games like Lost Planet and World in Conflict all scaled poorly, if any at all. The fact that ATI still doesnít provide the ability to setup custom game profiles for CrossFire rigs is also very disappointing.
Fortunately ATIís CrossFire drivers have come a long way since last year, and it appears that starting with the 3870 X2 ATI has taken CrossFire scaling very seriously. The only game that shows little scaling is Crysis, and to be honest this game has historically been a thorn in the side of both SLI and CrossFire (NVIDIA only recently improved SLI scaling with newer ForceWare 177 drivers). ATI has also been pretty good about providing custom hotfix drivers for the latest games when needed.
Ultimately at the end of the day it comes down to performance and image quality. As weíve shown you with our 8xAA benchmarks, clearly the Radeon HD 4870 X2 delivers in spades in both of these categories.
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