We've received many emails from readers asking about the phenomenon known as micro-stuttering and what it means to multi-GPU setups in CrossFire and SLI. After running plenty of benchmarks, we're ready to weigh in on what turns out to be a real issue.
Single GPU or multi-card setup? That's a question we face every time we start a System Builder Marathon series or evaluate the worth of a flagship GPU.
Do you want a just one high-strung racehorse or a pair, trio, or quartet of draft horses? Can a team of inexpensive cards perform the work of an pricier one and still come in at a lower cumulative cost?
Welcome to Groundhog Day. Due to recurring forum questions and direct requests by our readers, we decided that it's time to go beyond the usual performance-oriented benchmarks of CrossFire- and SLI-based systems, and shed some light on the underlying principles. Frame rates in and of themselves do not necessarily translate into a high-quality experience.
Yes, we're going to tackle the issue of micro-stuttering, which seems to keep so many sensitive eyes from investing in multiple cards running in concert. We'll also look at the scaling of two, three, and four GPUs. Where is the benefit? And at what point is actual added value really realized, or is churning out high (but ultimately useless) frame rates a self-defeating exercise? As we're sure you can imagine, at some point, the pursuit of performance can become a money pit and a power hog. At the same time, we've seen multi-card setups yield incredible value.

What Has Changed?
When it comes to measuring the scaling of mid-range cards, we run into a little problem. AMD and Nvidia try to limit the amount of expansion you can achieve with those less expensive boards by only exposing one bridge connector, limiting us to two-card configurations. Conversely, cards with two bridge connectors (enabling three- and four-way arrangements) are only found at the high end of the price spectrum.
For most folks, the prospect of anything beyond two high-end cards simply gets too expensive. Enter PowerColor's Radeon HD 6870 X2. It features two mid-range GPUs on a single PCB, consequently allowing us to set up and test four-way CrossFire with mid-range chips. As a result, we have the opportunity to compare a typical mid-range card like the Radeon HD 6870 (a $180 card) in a two-way setup to a single Radeon HD 6870 X2, and then add a three-way setup (Radeon HD 6870 X2 + 6870) and the four-way results.
Additionally, we compare those three configurations to a number of current cards, right up to the GeForce GTX 590, in a comprehensive set of benchmarks. Our goal is to evaluate performance, assess the seriousness of micro-stuttering, and finally rank the cards based on raw performance and their price/performance ratios. Are we due for a surprise? Nothing can be ruled out; we invite you to read on!
- Micro-Stuttering, Multi-Card Scaling, And More!
- How Do CrossFire And SLI Work?
- Micro-Stuttering: So Subtle, Yet So Annoying
- Step 1: CrossFire With Two GPUs
- Step 1: CrossFire With Two GPUs (Vs. SLI)
- Step 2: CrossFire With Three GPUs
- Step 3: CrossFire With Four GPUs (Vs. SLI)
- Test System And Benchmark Selection
- Benchmark Results: 3DMark 11 And Unigine Sanctuary
- Benchmark Results: DirectX 11 Games
- Benchmark Results: DirectX 10 Games
- Benchmark Results: DirectX 9 Games
- Tom's Hardware Performance Index
- Power Draw
- CrossFire, SLI, And Micro-Stuttering
Obviously, they won't reach frame rates as high as those attained through AFR, but if the frame rate loss is small enough, those modes might still be justifiable if they eliminate micro-stuttering altogether.
I'd be curious if these alternate methods could justify the cost of an additional card through added performance without coming with the drawback of micro-stuttering.
Obviously, they won't reach frame rates as high as those attained through AFR, but if the frame rate loss is small enough, those modes might still be justifiable if they eliminate micro-stuttering altogether.
I'd be curious if these alternate methods could justify the cost of an additional card through added performance without coming with the drawback of micro-stuttering.
AND i saw that Lucidlogix makes things worse on Radeon HD 6870 X2, what about the Lucidlocix Virtu, integrated in many motherboards, does it affects performance of your graphics card, and if it does how?
Based on the summary conclusion, does this mean Tom's has firmly gone back to recommending that users purchase "the most powerful single-GPU board you can afford" again?
SFR was really good back in the day and it was enjoyable as well stable. Also it scaled well for two way setups but Nvidia killed it off because of quad and tri was becoming popular back in 08. ATI has other rendering modes as well such as tile but they went the afr rout as well. The best days of sli and crossfire are over but one can still try to optimize their way out of some micro shuttering.
Toms could adopt this tool and use it to show the amount of MicroStutter along with their benchmark results. Many other sites like to show minimum fps in their graphs and I think showing the bottom 5% of frame times would be another way to show this problem up and compare the cards in your reviews.
-It's not about Bulldozer
-I would like to read some more detailed observations of problems you were seeing with crashing and driver issues
-A suggestion in the conclusion about what YOU would do with your own setups, as many of us want to know what the pros think
-It's not about Bulldozer