How to check compatibility of graphics card with motherboard

Upgrading an old PC with new hardware might sound like a recipe for disaster. Didn't some wise person once make a comment about putting new wine in old bottles? But you might be pleasantly surprised by just how far back you can go with desktop PCs and still manage to install a state-of-the-art graphics card. Nvidia RTX 2080 Ti and AMD Radeon RX 5700 XT GPUs, for example, can work in pretty much any PC built in the past decade—and likely even before that. But there are some caveats, particularly if your computer is getting a bit old and cantankerous. 

To make sure a new graphics card will work with PC, you’ll need:

• PCIe x16 slot on your motherboard
• Adequate clearance space in your case
• Power supply with both 8- and 6-pin PCIe Graphics (PEG) connectors
• CPU and RAM that are fast enough not to be a huge bottleneck

Do You Have PCIe x16? 

The tremendous backward compatibility of PCI Express ensures that even the newest, highest-end graphics cards can plug into a motherboard from the George W. Bush administration. From the original PCIe 1.0a/1.1 up through the latest PCIe 4.0, and even looking forward to future PCIe 5.0 and 6.0 standards, in theory, any card that can fit in a slot will work. You can put PCIe x1 cards in x16 slots, or have x16 slots with only x4 link widths, and everything in between. (There are potential exceptions, but mostly they're caused by bad implementations of PCIe or bad firmware.) That's pretty awesome when you think about it, especially in light of previous standards that were often deprecated. We won't shed even a single tear for the old ISA, VLB and AGP standards.

Upgrading your PC with a new graphics card is easy, then, assuming your PC actually has a PCIe x16 slot. If it doesn't, we recommend forgetting about upgrading just your graphics card. Theoretically you might be able to finagle an x1 to x16 PCIe adapter solution, but it's messy and just asking for trouble. If your motherboard lacks an x16 PCIe slot (see above), you should plan on upgrading your motherboard and likely your CPU, RAM and possibly power supply.

How Much Space in Your Case? 

That doesn't mean every old PC with a PCIe x16 slot can handle the latest graphics cards, but that's usually due to other hardware requirements. Size, for example: You're not going to fit a 320mm long graphics card into a case that only has room for a 270mm card. Many compact PCs will be restricted in what they can fit, and pre-built systems often fall into the compact category.

To find out how big your GPU can be, you could try looking at your case manual, assuming you have that. For pre-built PCs, you probably won't have it or be able to find the information online. We recommend going old-school and using a ruler or measuring tape — it will likely take less time and give you more accurate information.

To determine how long your graphics card can be, measure from the expansion slots on your case to whatever part is most likely to obstruct the graphics card on the other end. It doesn't matter if it's drive bays, fans, or the front of the case — just measure near your primary PCIe x16 slot (the one closest to the CPU cooler), as that's where your graphics card should go. Also pay attention to where the PEG connectors are located on whatever GPU you purchase. Most cards have them on the top, but some (eg, Nvidia's RTX 2060 Founders Edition) have them on the back. A tight fit at the back of your GPU could make it impossible to connect the power cables.

We recommend giving yourself some wiggle room as well. Even if you measure 300mm of clearance and a graphics card says it's 300mm long, it may be too snug a fit. Subtracting 20mm from your measurement and buying a card that's shorter than the resulting length should do the trick.

PSU Wattage Estimates 

These are approximate values, with recommendations based on having power to spare.

Do You Have The Right PSU? 

Power requirements are another major sticking point. If you have a PC that was built before 2015, there's a good chance your power supply won't have any 8-pin PCI Express Graphics (PEG) power connectors available, which are used on many of the faster cards today. 6-pin PEG connectors have been around much longer, but some budget power supplies still omit them. If you have a PC from a large OEM (eg, something from Dell, HP, or Lenovo), you might not even be able to swap out the power supply for a newer model with the required 6- or 8-pin connectors.

It's also important to note here that while 4-pin Molex to 6-pin PEG power adapters exist, as do 6-pin to 8-pin adapters, you really shouldn't use these! Melted wires, short circuits and even fires have been started with such shenanigans. Just buy a new PSU if you don't have the appropriate power connectors available.

If you need a new PSU, you can refer to the above table on recommended sizes based on how many PEG connectors a GPU needs. An 8-pin (or 6+2-pin) PEG connector can deliver up to 150W, and a 6-pin connector is for up to 75W. Not all PSUs are created equal, however, and we recommend getting an 80 Plus Gold or 80 Plus Platinum PSU — those are more efficient, which means less heat and noise from your PC, and usually cleaner power as well.

As for capacity,, you don't want to be at the limit of your PSU. For example, this EVGA 500W PSU (opens in new tab) has two 8-pin (6+2-pin) connectors available, and in theory could power even an RTX 2080 Ti. Your CPU, motherboard, RAM, and other components also draw power, however, and even if your PC is only using 400W, you probably don't want to be that close to the power supply's limit. In fact, optimal efficiency is often at 40-60% of a PSU's rated output.

Are Your Other Components Good Enough? 

Just because you can do something doesn't mean you should, of course. I have an old Intel Core i7-965 PC still kicking around that was an absolute beast back in early 2009 when I built it. More than a decade later, it can still do most of what you might want to do on a PC, and it has been upgraded many times over the years. It can even take a GeForce RTX 2080 Ti GPU, and it will run any game out there. What it won't do is run every game at high framerates.

The bottleneck in most cases isn't the PCIe 2.0 standard. Instead, it's the very-long-in-the-tooth CPU, coupled with the extreme GPU. But it does work—I've tried it and can confirm my 11-year-old PC fully recognizes and supports Nvidia and AMD's latest and greatest GPUs. How fast is an RTX 2080 Ti going to be on an older PC when compared to a new PC with a Core i9-9900K? We haven't run detailed benchmarks, but depending on the game, a Core i9-9900K can easily be over twice as fast as an old Core i7-965, and over three times as fast as an AMD A10-7890K. If you have an even older PC, or anything that only supports the PCIe 1.x standard, it's probably better to look at a full PC replacement rather than just upgrading your graphics card. 

Bottom Line 

Ultimately, like any upgrade in PC hardware, you want to consider your whole system. The good news is that if you have an old GPU fail, you can easily find a modern replacement that will still work—and it will probably be faster and support new features. Just verify that your PC has the required space and power connectors available, and a modern PCIe graphics card will work in any older PCIe slot. And if your PC pre-dates the PCIe era and has an AGP slot, it's time to put it out to pasture. Sorry. 

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Jarred Walton is a senior editor at Tom's Hardware focusing on everything GPU. He has been working as a tech journalist since 2004, writing for AnandTech, Maximum PC, and PC Gamer. From the first S3 Virge '3D decelerators' to today's GPUs, Jarred keeps up with all the latest graphics trends and is the one to ask about game performance.