Giving 3GB a Workout

Performance Impressions

In this section we will do some simple tests: use two notorious GPU memory hogs -Shogun 2: Total War and Metro 2033- to see how far we have to push things in order to reach the memory limit of a standard MSI Lightning (at its factory overclocked levels). We’ll then compare and contrast those results to those we encountered while using the 3GB Lightning XE.For Metro 2033 we used our standard gameplay playback.We decided to bypass Shogun 2’s built in benchmarking utility and instead use a playback from a custom battle. This effectively removes any CPU bottlenecks from the equation since AI is disabled in playback mode. Additionally, the config file was modified to allow the 1.5GB card to read as having 3GB of texture memory available which is necessary as any other option would limit the available video card settings.First up we have Shogun 2, an impressive looking game when DX11 is enabled but it is also extremely tough on hardware. As a purely anecdotal point, we read a whopping 2.1GB of texture memory being used at 2560 x 1600 with 8x MSAA enabled.It seems like even with such a demanding game, the core actually becomes the bottleneck here rather than the available memory bandwidth. The 3GB card can easily win when the settings are cranked but it doesn’t make a difference since playable framerates were impossible to achieve with MSAA enabled at 2560 x 1600 regardless of the card being used. At 1920 x 1200 up to 4x MSAA things are a bit easier but since available video memory wasn’t an issue, both cards drew even.Metro 2033 shows much of the same thing as Shogun: the 3GB framebuffer does make a difference but once again the GPU itself becomes the limiting factor when asked to push around massive rendering workloads. On the positive side of things, the 3GB card was actually able to play Metro 2033 with everything maxed out….albeit at a paltry 17 frames per second. Minimum framerates on the other hand were absolutely dominated by the Xtreme Edition.As you may have already observed Lightning Xtreme Edition’s performance in all of our tests (including those above) was interesting to say the least. The majority of our tests obviously just didn’t push the 1.5GB Lightning’s memory bandwidth past its breaking point. However, in other cases we saw that at high resolutions with extreme instances of MSAA, additional bandwidth can at the very least increase minimum framerates.First up we have something that shouldn’t be too much of a shocker. On single monitor systems the current crop of DX11 games just isn’t bandwidth limited on a 1.5GB 384-bit card like the GTX 580. You’re much more likely to run smack into a rendering limitation rather than a situation which demands excess memory. All the video memory in the world won’t save your card’s bacon if its core struggles to process draw calls. Not once did the expanded GDDR5 layout provide playable framerates in situations where the 1.5GB version struggled.This isn’t to say that 3GB GTX 580 cards are pointless in today’s market. It is quite obvious that the second generation DX11 games like Metro 2033 and Shogun 2 have a voracious appetite for memory resources and upcoming titles will likely do little to change this trend. So it is conceivable that within Lightning XE’s expected lifecycle there will be a few titles which will benefit from its expanded memory allotment…but only when playing at ultra high resolutions with anti aliasing pushed to mind boggling levels.We saw throughout the standard battery of tests that memory controllers have additional overhead due to the increased memory allotment per controller. Memory latency has also increased through the use of 64x32 modules rather than the reference version’s 32x32 module layout. The result is a negligible framerate decrease when compared to 1.5GB card. It is for this reason that we highly recommend choosing wisely when looking at GXT 580 cards; if you’re using a 24” or smaller monitor, better performance is attainable by less expensive 1.5GB cards.