Multi-GPU Setups: The Basics Of CrossFire And SLI
Table of contents
- 1. AMD Or Nvidia?
- 2. Driver Installation On Nvidia Cards
- 3. Driver Installation On AMD Cards
- 4. Connectors
Motherboards with multiple PCIe slots are becoming the norm these days, and the trend is being fueled by multi-GPU configurations. Configuring Nvidia's SLI and AMD's CrossFire technologies is easy, but how much more performance can you expect from them?
AMD calls it CrossFire, Nvidia calls it Scalable Link Interface (SLI). In essence, both companies are using a similar concept to distribute the workload presented by your favorite game across two, three, or four graphics cards.
Installing a multiple graphics card setup can be a bit tricky, and there are several questions you need to answer. How fast must the PCI Express slots be (we'll have a story posted next week addressing this one in depth)? Do you need a bridge connector between the cards? How powerful should the CPU be to make proper use of this graphics muscle? We asked ourselves these questions, ran scaling tests, compiled the results, and came up with some great tips for you.
In order to evaluate how SLI and CrossFire scale with CPU performance, we increased the default 2.66 GHz clock rate (133 MHz x 20) of our Intel Core i5-750 reference processor to almost 4 GHz (190 MHz x21) by modifying the base clock and multiplier in the BIOS. On all Intel processors with Turbo Boost feature (that aren't Extreme Edition or K-series parts), you can only increase the multiplier by one increment. We used a Gigabyte P55A-UD7 motherboard and disabled Turbo Boost. The number of CPU cores remained unchanged.
Unlike many other platforms, which are limited to CrossFire, our our P55-based Gigabyte board supports both CrossFire and SLI, making it easier to keep the platform consistent.
| Nvidia and AMD Graphics Test Setup | |
|---|---|
| CPU | Intel Core i5-750 @ 4 GHz (190 MHz x 21), Lynnfield, BIOS 1.26875 V, 45 nm, LGA 1156 |
| Motherboard | Gigabyte P55A-UD7, PCIe 2.0, 3-Way SLI, SATA 6Gb/s, USB 3.0 |
| Chipset | Intel P55 Express |
| Memory | OCZ3G2000LV4GK, PC3-16000 Golden Series, 2 x 2 GB DDR3, 2 x 570 MHz 7-7-7-19 |
| Audio | Realtek ALC889 |
| LAN | 2 x RTL8111D |
| HDDs | SATA, Western Digital, Raptor WD300HLFS, WD5000AAKS |
| DVD | Gigabyte GO-D1600C |
| Power Supply | Cooler Master RS-850-EMBA 850 W |
| Drivers and Configuration | |
| Graphics | AMD Catalyst 10.4, Geforce 197.45 |
| Operating System | Windows 7 Ultimate 32-Bit |
| DirectX | 9, 10, and 11 |
| Chipset Driver | Intel Chipset Installation Utility 9.1.1 |
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Good article. Totally agree with difference in ease of setup having gone from a pair 8800GTX OC2's in SLI to 5850's in crossfire, I miss my 8800GTX monsters they were great cards. Also agree about processor speed. I'd noticed in a few games (some are more noticeable than others) the framerate would slowly decrease then spring back up again, it was bugging me hugely. It was most noticeable in Dirt and Grid, two games I hadn't played since my old E6850 with the 8800's. Ran a fraps benchmark and you could see it cyclicly droping down through numbers 120, 118, 114, 110, down to 94fps, then jumping back upto 120+ and decreasing again. I ran Core Temp and straight away I could see the multiplier starting at 16 then dropping increntally down to 12 then jumping back up to 16. So I kept the voltages all stock and increased the baseclock to 160MHz, Loaded up the game, the multiplier now stays at 12, but the framerate is stable at 120-124fps with a processor speed of just under 2GHz. But at stock clocks why wouldn't the multiplier not just stay at 16?
This is on an i7 930, GA-EX58-UD5, 6GB 1600MHz DDR3, 2 Sapphire 5850 Toxic GPUs, and Win 7 64bit.
ATI doesn't have terrible drivers, nVidia does.
Well, ATI has some problems with Crossfire but remember that you can mix up different cards but with SLI you can only use the same card from same manufacturer. This might explain why drivers fail with Crossfire setup.
cmon what's with all these spam?..
I know, it's getting stupid, and the mods don't seem to be doing anything about it.