Monday, October 18, 2010

AMD CrossFire Vs. Nvidia SLI Scaling Analysis

We’ve seen impressive performance from Nvidia's GeForce GTX 460 when it's matched up with a second card in SLI mode. But how does the entire high-end GeForce GTX 400 line compare to Radeon HD 5000-series cards? We test them all in several popular games.

The new GeForce GTX 460 made us sit up and take notice, particularly when we paired them up in a dual-card SLI configuration. As our own Thomas Soderstrom showed, two GeForce GTX 460s in SLI can even outperform Nvidia's GeForce GTX 480 flagship.

Nvidia recently began a bit of a price war with AMD. Retail prices for graphics cards like the GeForce GTX 470 and 480 are plummeting, bringing the fight to AMD’s doorstep. GeForce GTX 470s are selling for as little as $279; GeForce GTX 480s are going for $450 on Newegg.

With a one-year head start and plenty of margin in its pocket, AMD isn't too proud to engage in a bit of a brawl. Radeon HD 5850s are $260 all day long on Newegg, and rebates are taking these cards as low as $210.


This news forces us to challenge preconceived notions of relative value. It lets us know that it’s time for a thorough Radeon HD 5000- vs. GeForce GTX 400-series performance analysis. Today we're testing the Radeon HD 5830, 5850, and 5870, along with the GeForce GTX 460, 470, and 480 to provide a thorough understanding of how these cards perform relative to one another in both single- and dual-card configurations.


There’s not much else to say. Let’s get ready to rumble!

Our charts list the graphics cards based on their retail prices, from the most expensive configuration on the top to the cheapest on the bottom. Our testing involves a number of graphics cards from many manufacturers, so we are setting all of the clock speeds to reference levels to keep things on an even playing field.


There is one testing configuration that we have to simulate: two Radeon HD 5850 cards in CrossFire. We only received a single Radeon HD 5850 in time for testing, so we’re pairing the card with a Radeon HD 5870. AMD has confirmed that the superior card will be crippled when these models are paired in CrossFire, resulting in Radeon HD 5850-class specifications, using 1440 of its 1600 stream processors and 72 of its 80 texture units.

We've set the clocks of both cards to Radeon HD 5850 reference speeds; the resulting performance should be exactly the same as two of these cards in CrossFire. The results show the performance exactly where we would expect a Radeon HD 5850 CrossFire configuration to be relative to the Radeon HD 5830 and Radeon HD 5870.

Test System

Intel Core i7-920 (Nehalem), 2.67 GHz, QPI-4200, 8 MB Cache
Overclocked to 3.61 GHz @ 172 MHz BCLK


Gigabyte X58A-UD3R
Intel X58, BIOS version FA

Onboard Gigabit LAN controller

Mushkin PC3-10700H
3x 2048 MB, DDR3-1376, CL 10-10-10-25-1T


Nvidia GeForce GTX 480 Reference
1536 MB GDDR5
Zotac GeForce GTX 480 AMP! Edition
1536 MB GDDR5
HIS HD 5870 iCooler V Turbo X
Radeon HD 5870, 1 GB GDDR5
Gigabyte GV-R587SO-1GD
Radeon HD 5870, 1 GB GDDR5
MSI GeForce GTX 470
1280 MB GDDR5
Gigabyte GV-N470SO-13I
GeForce GTX 470, 1280 MB GDDR5
Gigabyte GV-R585OC-1GD
Radeon HD 5850, 1 GB GDDR5
AMD Radeon HD 5830 Reference
2x Gigabyte GV-N460OC-1GI
GeForce GTX 460, 1 GB GDDR5

(all clock rates have been set to reference specifications for the purpose of benchmarking)

Hard Drive

Western Digital Caviar WD50 00AAJS-00YFA,
500 GB, 7200 RPM, 8 MB cache, SATA 3.0Gb/s


Thermaltake Toughpower 1200 W
1200 W, ATX 12V 2.2, EPS 12v 2.91

Software and Drivers
Operating System
Microsoft Windows 7 Ultimate 64-bit
DirectX versionDirectX 11
Graphics Drivers

AMD Catalyst 10.7 Beta, Nvidia GeForce Driver 258.96 WHQL

Just Cause 2 is part of Nvidia’s The Way It's Meant To Be Played (TWIMTBP) program, but it doesn’t seem to favor the GeForce cards in SLI over Radeons in CrossFire. When it comes to single-card performance, the GeForces do perform a little better than the similarly-priced Radeons.

At 2560x1600, the GeForce cards in SLI fare a little better. It may be the extra video RAM on the GeForce GTX 470 and GeForce GTX 480 that is helping out here.

Aliens vs Predator performance matches the price curve rather conveniently. There isn’t too much to talk about here, except for a slight minimum frame rate drop for CrossFire cards. But benchmarking experience shows us that this happens at the beginning of the benchmark and the game runs quite well once it’s in the thick of things.

StarCraft 2 is clearly bottlenecked by our host platform. But CrossFire is performing very poorly here in comparison to the competition, with the single-card performance faring better than two cards in CrossFire mode. Hopefully, AMD will address this problem with a Catalyst Control Center profile update in the near future.

Power use stays relatively close to the performance curve we have experienced, although the Radeon HD 5870 in CrossFire does show itself to be more power-friendly than the GeForce GTX 470 and GeForce GTX 480 cards in SLI.

Remember, we’ve organized this chart by listing average prices from the lowest on the bottom to the highest on top. At 1920x1080, it appears that CrossFire and SLI performance scales right along with price. Of course, the spread between certain graphics cards is quite close--the most notable example is the GeForce GTX 470 that can be purchased for right around $280, while the 5850s are going for about $260 now.

In general, the lower-end GeForce GTX 400 cards are putting solid pressure on the competing Radeon solutions, and as a result, we've already seen a noticeable Radeon HD 5000 series price drop to keep the AMD cards in line with the competitor’s price/performance ratios.

At 2560x1600, we see a definite performance drop from the Radeon cards in CrossFire. As we mentioned in the benchmarks, at least some of the blame for this can be attributed to the 1 GB frame buffer on Radeon cards while the competing GeForce GTX 470 and GeForce GTX 480 have 1280 MB and 1536MB, respectively, giving them breathing room when it comes to high resolutions mixed with demanding AA settings. In single-card configurations, the Radeons don’t seem to mind the RAM deficit. But in CrossFire, these cards certainly seem to be experiencing some kind of RAM-related bottleneck when pushed hard.

ZoomFrankly, there aren’t a lot of 2560x1600 monitors out there in the wild, so this probably isn’t a major concern for most folks. But for gamers planning on a high-resolution 30” monitor or a triple-monitor gaming rig, GeForce GTX 470/480 cards or Eyefinity Edition Radeon cards with 2 GB of RAM will be something to look into.

We hope to revisit the 2560x1600 resolution performance with 2 GB Radeon cards in CrossFire to see if more video RAM clears up the inconsistency. For those of you running 1920x1200 or lower resolutions, there is a lot less to worry about when putting together your hardcore gaming rig.

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