Is vertically mounting a GPU bad for thermals?

A recent trend in the DIY PC world is taking a GPU out of its PCIe slot on the motherboard and mounting it vertically on the shroud in the bottom of the case. This lets people show off their GPU as you can see the cooler and shroud much better. Installing a GPU vertically will usually have a negative impact on GPU temps, however, so it’s typically done purely for aesthetic reasons, not to improve performance. There are two reasons why it can impact temperatures negatively, so let's examine each one individually.

When you relocate your GPU, you have to install a ribbon cable into its PCIe slot, then connect the cable to the GPU in its new orientation. It's typically mounted in pre-drilled holes on the bottom of the case, or in an add-on bracket. The PCIe cable connecting the two components needs some room to flex, so this means your GPU is usually pushed away from the motherboard by a few inches, which can position it too close to the side panel.

This proximity to the panel can reduce the amount of fresh air available to enter the GPU fans. In contrast, when the GPU is sitting in the PCIe slot in the motherboard, it has access to fresh air coming into the case from the front intake and/or the fans on the bottom of the case, and it usually has plenty of room to "breathe," but vertical orientation changes that significantly in some cases.

The real question here is just how close is the GPU to the side panel? If it’s right up next to it, the GPU will not be able to get as much fresh air as it would if it was installed horizontally. This will normally cause temps to rise, so the question then becomes how much leeway do you have to increase temps?

A GPU will run just fine all the way up to its TJmax temperature before it starts to throttle its clocks down to keep temps in check, but most people don’t want their GPU running that hot. TJmax is typically around 95C or so, which is much hotter than most people are comfortable with, as ~70C is typically the sweet spot for a GPU under full load. However, as always, the cooler the GPU runs the higher its clocks will be, so lower temps are always better for performance.

Therefore, if your GPU is running at 65C horizontally, you can add 10C without breaking a sweat. However, if it’s already running at 75C, a vertical installation might make it too toasty for your liking. That said, the temperature increase that occurs is the result of how close the GPU fan are to the side panel, and that can vary according to how big the GPU is, and where the holes are pre-installed in your case.

Also, some people use a bracket to accomplish this “upgrade” instead of using pre-drilled holes in the shroud, which can give the GPU a bit more room, but there’s an extra expense added here for the bracket, so you’ll need to figure out if you think it’s worth it.

A lot of high-end GPUs use vapor chambers to help with cooling, and these are typically designed based on a horizontal installation of the GPU. These chambers feature a small amount of liquid in a flat chamber directly on top of the GPU die. When heat is applied, that liquid turns into gas and rises up to the top of the chamber, transferring the heat to the connected heat pipes, then returning to the bottom of the chamber when it is cooled so the cycle can begin once again.

When a GPU is installed horizontally, that can cause the liquid to pool at the bottom of the chamber, making it difficult for the gas to rise high enough vertically to be continue the heating/cooling cycle, which could impact thermals.

Because of this situation, some people who are planning on a vertical GPU mount stay away from GPUs with vapor chambers, but the rub is it’s difficult to figure out exactly which GPUs have them and which ones don’t. You have to do some subtraction as vendors that use them typically mention them in marketing materials, while a GPU without one will just say nothing at all other than it has heat pipes, usually.

That said, it really comes down to trying it out and seeing what the temps are like, as it’s hard to predict how a certain GPU will perform in a variety of cases with different kinds of vertical mounting installations being applied. The airflow inside a case is a big factor too, so there's several variables to consider.

Most of the time, mounting a GPU vertically will increase your temperatures, but it could be by just a few degrees, or 10 degrees, and it’s impossible to predict the specific outcome as it’s based on the GPU and case involved. In general, the best outcome is there being no change in temps from horizontal to vertical, but that is the exception, and it all depends on your case, airflow, number of internal fans, etc.

The best way to approach this task is to think about how close the GPU will be to the side panel, and whether or not you think that will allow it to have sufficient airflow or not. If the answer is you think it’ll be too close, you will need to look at an aftermarket bracket for your case, or a different case. Either way, you will typically not know what temps will be like until your GPU is installed vertically, and you can test it to see how it performs. There’s always Google, of course, but you might not be able to find someone with your GPU and your case to use as a reference.

Also, if you wanted to sidestep all these issues, you could always liquid cool your GPU since airflow doesn’t matter in that situation, but that’s obviously a lot more expensive and time consuming than a simple DIY project. Still, if you’ve been looking for a reason to dabble in custom liquid cooling, here it is!