FCAT Frametime analysis

Frametime and latency performance

With FCAT we will look into Frame Experience Analysis. Basically with the charts shown we are trying to show you graphics anomalies like stutters and glitches in a plotted chart. Lately there has been a new measurement introduced, latency measurements. Basically it is the opposite of FPS.  

• FPS mostly measures performance, the number of frames rendered per passing second.
• Frametime AKA Frame Experience recordings mostly measures and exposes anomalies - here we look at how long it takes to render one frame. Measure that chronologically and you can see anomalies like peaks and dips in a plotted chart, indicating something could be off. 

We have a detailed article (read here) on the new FCAT methodology used, and it also explains why we do not use FRAPS anymore. Frametime - Basically the time it takes to render one frame can be monitored and tagged with a number, this is latency. One frame can take say 17 ms. Higher latency can indicate a slow framerate, and weird latency spikes indicate a stutter, jitter, twitches; basically anomalies that are visible on your monitor.

What Do These Measurements Show?

What these measurements show are anomalies like small glitches and stutters that you can sometimes (and please do read that well, sometimes) see on screen. Below I'd like to run through a couple of titles with you. Bear in mind that Average FPS often matters more than frametime measurements. 

Above, the percentile chart of a 31 second recording @ 2560x1440. Here we plot FPS and place it in relation to percentiles. 50% of the time measured frames is the average framerate (higher = better). And yeah, you can already see, something is off.

For a GeForce GTX 1060 we cannot see a significant enough glitch or stutter in frame-time scaling (chart wise) that is significant or long-lasting. Two small drops, which is nothing.

AMD then, I call instrument error. There was something totally freaky weird in the measurements, as you can see. We have not been able to track what this is, however, is NOT VISIBLE ON SCREEN. Ergo, I call instrument or measurement error. We performed the test multiple times, we also performed it on an RX 580, R9 390X and Vega, all show this weird pattern. Again, you cannot see this, so this is something on our end! However, we post/report what we measure and see, ergo for the sake of objectivity we include this. The game runs great on the AMD Radeon RX 580 tested!

Update: we ran a contra test / extra trace with perfmon, which confirmes my expectations. That looks much far more normal.