March 1

PC Graphics Cards for Sim-Racing

­­I frequently get asked about graphics cards for sim-racing PCs. Which model? Should I do multiples? Which brand? Why can’t I use the one already in the PC. These are all good questions and I’ll try to cover them all.

The Job of the GPU

First, let’s talk about the role of the graphics processing unit, or GPU, vs the CPU where it pertains to graphics. In a sim-racing PC (SRPC), the job of the CPU is to figure out where everything is on the track. It calculates where every car should be, where the pavement is and where the grass is, where the trees are located, where the barrier is, where the grandstands are, the course workers, the shapes of all these objects and most importantly it figures out where the player is standing, what direction the player is facing and where the light sources are located. It then gives all this information to the GPU along with image files of what every object looks like. These image files are called textures and they are used to ‘wrap’ the shapes so they look like the objects they are supposed to be.

It then becomes the GPUs job to figure out what objects can be seen by the player, what objects are obstructed by other objects, what objects can be seen through other objects such as glass and smoke, where the shadows land, what can be seen in reflections, what sides of the objects are illuminated by the light sources and which sides are in the dark, and many more details. Finally, it smoothes and blends the colors together to make the image look natural.

Since a moving picture is really just a series of still images flashed quickly one after the other, this process has to repeat for every frame. To get smooth video, the human eye needs to see 60 images per second, this where the 60Hz refresh rate comes in. There are monitors that are capable of faster refresh rates but for your GPU to handle them they need to perform the above operations at a faster rate.

Please understand that there is a lot of work that a GPU has to perform in a very short amount of time, 1/60 of a second at most. Unless you have an extremely powerful GPU, it typically cannot do everything it needs to do in such a short amount of time. When it can’t finish “painting” the image in the allotted amount of time, the monitor then displays the same image as the previous frame as a placeholder. The resulting effect is a stutter in the video. Most often this only happens during difficult images to generate and can last for several consecutive frames which results in frames only updating 30 times per second which makes the race seem like its moving in slow motion, similar to strobe lights at a nightclub.

Typically there are two ways to solve this, either get a more powerful GPU or turn down the details in the image. Often times, it’s a combination of both. All PC games have a graphics settings screen where you can turn on/off various details that require significant time to render. Details such as smoke, shadows, spectators, images in the mirrors, etc. These details can be turned off without affecting the driver’s performance in the race. Surely, anyone can drive a car that doesn’t cast a shadow, or that doesn’t generate smoke.

The Perfect Video Card

So the point of this long involved explanation is to demonstrate why there is no perfect answer to the question; which graphics card should I get? It is by far easier for the game developers to add more visual details than it is for the GPU designers to make a GPU that can handle it. So my answer would be spend at least $150 on a graphics card and buy the most powerful you can afford.

Single-Monitor Graphics Card

I am an nVidia partner so I am most familiar with their product line, so my recommendations will be based these products. For a single monitor setup I recommend the GTX 660ti or above. Get one with the largest capacity of VRAM (video memory) available. These graphics cards are not only cabale of driving most common displays, but they can also run most simulation titles in 3D using 3DTV which can be unlocked by purchasing a small piece of nVidia software. The graphics cards are also equipped with G-Sync, an nVidia technology which allows the refresh rate of the monitor to adjust to the speed of the GPU.

This single graphics card can handle triple surround monitors by simply adding an additional identical GPU card with the same amount of memory. For simplicities sake, I always recommend using two identical card brands and models. While this is a great option for those of you that want to start with a single monitor and upgrade as you get more serious, I recommend a more powerful graphics card for those looking to build a triple monitor solution from the start.

Triple-Monitor Graphics Card

For those looking to get a graphics card specifically for triple monitor sim-racing, I recommend a single high-end graphics card, a GTX 790 or even the GTX 980 graphics card. The reason is pretty simple, the video memory is optimized. Each GPU needs its own bank of memory to perform its job. When multiple graphics cards are used, each graphics card keeps the same information in memory rather than sharing the memory. As a result, you may have purchased two graphics cards with 4GB of memory on each, but you don’t get the performance of 8GB, only the performance of 4GB.

Conclusion

If you are planning on a single monitor setup, then get an upper-midrange graphics card. If you think you will ever want to upgrade to a triple monitor setup, the get a high-end graphics card. In short, I only recommend building a system with two or more graphics cards when those graphics cards are the most powerful already in existence. In other words, the only reason to use multiple graphics cards is to achieve performance that exceeds the currently available GPUs.

Please remember that in order to implement multiple nVidia graphics cards your motherboard must be nVidia SLI certified. This insures you get the most out of your multiple graphics card setup. If you have any questions on this post or a suggestion for other topics, please leave a comment. Thanks.


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Posted March 1, 2015 by Frank in category Technical Articles

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