One thing that I have really had trouble understanding properly, are the iRacing performance bars. So i had a closer look at them, and the information available, to try and sort them out. Although I will try to explain what these bars show, based off what i could gather from the internet, I sadly can’t get into exactly why they show what they do. This seems to be more complicated, than even iRacing support can figure out some times. Non the less, it is a good and detailed explanation of all the performance bars that display on the FPS black box.
The first thing you’ll need to know, is that you can chose what bars you want to display. When you’re in the sim head to options, and in the tab called Options, you’ll find the On Screen Display options. Here you can choose to have them disabled, shown graphically, or shown numerically
You’ll notice that they are grouped in different categories, and this is the first step to understanding them. Instead of a list of letters with status bars, you might notice that they are grouped, into four groups. There is a very slight gap between these letters, on the black box, that maybe is more visible now that you know that they are meant to be grouped.
|Graphics||: R & G|
|Network:||L & Q|
|System:||C & S & P|
Please note, that if the Simulation determines that it seems to be having critical performance issues (ie issues that are causing it to fall behind the race server) some of the displays will be forced on, even if you currently have them hidden. The labels of the meters that indicate the performance issue will be flashed.
F for Force
Lets start with the last letter on the list, as it is the easiest of them all. The F bar shows you the strength of the Force Feedback that your wheel is giving you. You want to keep the forces below 100% so that the wheel is not over-saturating, but still high enough that you are using the full range allowable from your wheel. You can adjust this while you’re in the car, and driving, by using your F9 black box. Here you can either set it manually, or after running a lap or two, select the “auto” option, that will set it to the proper value, depending on the track you’re driving on.
Red indicates you have 100% torque saturation or more, yellow indicates you have 85% to 99% torque saturation, and green indicates 84% or less torque saturation. This bare will only show if you’re in the car – it will disappear if you exit the car into the menu
R for Renderer
This is one of the bars that really felt confusing for me. It turns out that it actually is two bars on top of each other! This meter shows a 1-second running average of how much time it is taking for the iRacing graphics engine to build the set of commands that tell the graphics card how to draw each frame. An empty bar means it is taking 0 seconds, and full bar means it is taking 1 second. A purple bar is shown beneath this one, and shows the 15-second running average.
If you set this to display a numerical value, it will show the value in milliseconds, but only for the 1-second running average
G for Graphics
Similar to the bar above, this is also a stacked bar. It also shows a 1-second running average of how much time it is taking your graphics card to draw the displayed frames. Basically this is a status of how your GPU is performing. An empty bar means it is taking 0 seconds, and full bar means it is taking 1 second. A purple bar is shown beneath this one, and shows the 15-second running average. If you have this set as a numerical value, it will show the average time in milliseconds but only for the 1-second running average.
L for Latency
The first bar in the network category is for latency between your computer and the race server. Network latency is the term used to indicate any kind of delay that happens in data communication over a network, but will often be caused by your router or modem and some times hardware like a slow hard-drive. There can be many other reasons too though.
An empty bar is 0ms of round-trip network latency between your computer and the race server, while a full bar is 1000ms (one second) of latency. If you have set this to a numerical value, it will display latency in milliseconds.
Q for Quality
There are many ways one would describe the quality of a connection, but here, it will describe packet loss. I am no expert in this, so me trying to explain it might sound stupid, and might be wrong. So if you really want to learn about this, do so somewhere else. From what i can understand, some time, when you press a network or a link in the network to more than what it was designed to, it will kick off some of the data that it was meant to transmit. TCP will make sure that this data gets resent and even out the rush of data, so packet loss should not affect performance noticeably. It might though, if there is too much.
This bar is two sided. One side (the left-side) measures the incoming network packet loss to the comluter from the race server. The right-side meter measures the incoming packet loss on the race server from your computer. An empty meter is 0% packet loss, and a full meter is 50% packet loss.If you have set this to a numerical value, it will show the percentage of packet loss
C for CPU
Overall, the core of iRacing on your PC, runs 60 times per second, although some parts run at a higher rate. To keep-up with the simulated world, it must complete an “update” in less than 1/60th of a second, otherwise it will start falling behind. This bar, shows how well your PCs CPU keeps up with this rate of calculations, to keep up with what is going on.
This bar is also a stacked one, where you can see two bars on top of each other. The bar will show a 1-second and a 15-second-long running average of the percentage of that 1/60th of a second the simulation is taking to “run the world”. An empty bar means 0% of that 1/60th of a second is being used, while a full bar means at least 100% is being used, but it could actually be “running long”. If the simulation keeps “running long”, it will begin to fall behind “real time”, leading to time Skew between your Simulation and the server. If you have set this to a number value, it will display as a percentage of the allowed 1/60th of a second that the Simulation is using to update the world.
S for Skew
This is where it can begin to get a bit too technical, and to be honest, I am not sure about what I am trying to explain. From what i understand, the game server keeps track of the “world” that you’re racing in. This means that the server you connect to, knows what is going on, and if all was right, what your computer calculates, should correspond to what the server has. Skew happens when there is a difference between the simulation-world time on your instance of iRacing on your PC, and the correct simulated-world time at the race server.
While small flickers of Skew can appear due to “network jitter” the most significant amounts of Skew are almost always caused by your computer being unable to perform the calculations necessary to keep up with real time, as discussion above, for the C bar.
This is a special bar that has 0 in the middle and can expand towards both directions. An empty bar means your simulation is in sync with the server. As the meter grows to the left from the center, your system is falling behind the server, and the bar will be full-left when the Sim is 1 second behind. As the meter grows to the right from the center, your system is getting ahead of the server, and the bar will be full-right when it is 1 second ahead. If you have set this to numbers, the measurement will be is in seconds.
P for Paging
This one is a bit technical too, but to oversimplify it, it is about RAM. If you have problems with this bar, you either have too little RAM, too slow RAM, or your OS is having trouble administering the usage of RAM.
Paging is the term that covers how the operating system manages the attachment of physical RAM memory to a program’s virtual memory addresses. When the OS must intervene in the virtual<->physical memory attachment, that causes a “page fault”. “Hard” page faults are when the operating system must transfer data between physical RAM and your disk (or SSD). These can greatly affect the performance of your system.
The bar will display hard page faults in green or yellow, and the meter will be full-yellow at 30 hard page faults/second. If you have this set to a numerical value, it will display the number of hard page faults per second.