We mostly saw differences centered around the 1.87% to 2.5% area.
1190MHz differential over here, if you're curious about what kind of delta that produces. SLI overclocking is being done in one of our next tests and has been reserved for that content. No overclocking was applied during these tests, which does mean that the slower of the two cards (the 970 Hybrid, at 1140MHz) will marginally impact the overall performance.
This is another point that could potentially favor a single, higher-end GPU, but recent optimizations made to drivers and games may reduce the impact to manageable territory – we'll look at that below.
AMD CrossFire setups, as of driver version 15.7 from July 2015, also fully support FreeSync.Īnother performance consideration for multi-GPU cards – in a similar vein to micro-stutter – 1% and 0.1% low frame performance can sometimes be worse than single-card setups. The GPU connected to the display manages the sync technology. Monitors supporting G-Sync and FreeSync are of particular importance for consideration when running SLI or CrossFire. Adaptive synchronization technologies have helped to mitigate this phenomenon.
jumping from a 16ms render to a 30ms or 40ms render time (or worse). Micro-sutter is observable as a result of disparate frame-time gaps, where the time between frame renders is inconsistent enough that the user can perceive a jarring difference – e.g. In these situations, disabling one of the two GPUs (but leaving the GPU physically installed) will reduce or eliminate micro-stutter, but then you're only getting half the investment outputting – certainly an unwanted situation. Micro-stutter can be so extreme in some games and driver sets that SLI becomes undesirable, even if average FPS is improved over single-card configurations. GPUs render alternating frames when using the AFR technique more explicitly, GPU A will render all odd frames (1, 3, 5, 7) while GPU B renders all even frames (0, 2, 4, 6).
SLI and CrossFire are also historically prone to micro- stuttering as a result of their dual-processing technique (normally AFR, or alternate frame rendering). It's almost always better to buy a newer, single card once that happens, as the spiked prices are hardly sane or good value. Almost every time a card exits official production, prices spike on retailers and second-hand markets. Also in that scenario, we'd always recommend buying that second card (if truly desired) before it exits production. In the event of the first scenario – where the user already owns one GTX 970 and is considering a second – the value considerations are different and will be discussed only in the conclusion.
There are two primary scenarios where SLI or CrossFire are used: A later upgrade when half the configuration is already owned and a day-one, brand new build. That makes the value comparison clean and easy, no waffling between price. We're also assuming a joint price of ~$660 - $700 for two GTX 970s (non-liquid), which puts them effectively at a head-to-head price bracket. For this test, we're assuming a baseline price of $650 - $660 for a single 980 Ti (MSRP is $650, which is where most non-liquid cards fall). The “Hybrid” cards drive price up a little higher than the average for a 970 SLI or 980 Ti single card setup.