Graphics cards are expensive, and none are more expensive than Nvidia's RTX 50 series. With that expense comes a rise in the counterfeit GPU market, a market designed to prey on those who may be looking for a bargain on a shiny new piece of hardware. Fakes range from ridiculously simple to incredibly sophisticated, and from the outside, it can be hard to tell if you have a legitimate or a fake.

But how do they work? How can you tell if you have a counterfeit GPU? There's a lot going on here, but it's important to note that if you bought your GPU from a reputable vendor, it's almost certainly legitimate.

How are counterfeit GPUs made?

BIOS tweaks are the main way

Counterfeit GPUs are rarely totally counterfeit. Most of the time, they take older GPUs and reflash their BIOS so that the card identifies as a newer one to the system. This might mean taking an RTX 3080 Ti (a still powerful card in its own right) and pawning it off as a shiny new RTX 4090, without the buyer suspecting a thing. This has actually already happened, where the seller went so far as to polish the surface of the RTX 3080 Ti core (GA102) and etch the markings from the RTX 4090 core (AD102) onto it instead.

That's just the hardware side of things though; in software, there's still work to be done. Someone selling a counterfeit GPU will likely also reflash the BIOS so that the card identifies as a different one, and it may even falsely report how much VRAM is available, the features that it supports, and the PCIe lanes that it's using. Tools like nvflashk can reflash an Nvidia GPU, and it's likely that this tool (or a similar one) is used in the process.

Things can even go a step further than that, with the seller potentially providing modified drivers to the end-user that handles spoofing for them. This is significantly rarer as it can arouse suspicion, especially when BIOS reflashing will get the job done and will still allow for the end-user to install GPU drivers straight from Nvidia.

For what it's worth, there are legitimate reasons to flash the BIOS of your GPU. Sometimes, people will flash a BIOS from the same card but from a different brand in order to achieve higher power draw, allow for a lower idle power draw, or even overclock more. This might break some features, though. For example, if your card has three DisplayPort outputs and the card you're flashing the BIOS from only has two, then your third DisplayPort might stop working.

Modifying a BIOS is significantly more sophisticated, and requires taking an Nvidia BIOS file and editing it. You can either use a hex editor or tools similar to Kepler BIOS Tweaker for older cards. For the most part, people will simply crossflash BIOSes from other cards in order to do things like raise the voltage limit or power limit.

How can you tell if you have a fake GPU?

GPU-Z is your friend

When it comes to spotting a fake, the quickest and easiest way to tell is through a tool like GPU-Z. It will identify and prefix the name of your card with "[FAKE]" beside it so that you can dig deeper and try to find more information. Cards don't typically fool GPU-Z, so you'll instantly be able to tell. On top of that, even if it doesn't say "[FAKE]", other information like the technology or release date might be incorrect.

Another way is to check what the latest driver version you can install is for your GPU before it stops working. A few years ago, there were many fake Nvidia GTX 1050 Ti cards that were actually a GTX 550 Ti under the hood. These cards reached end of life with driver version 391.35 from Nvidia, meaning that it stopped receiving updates. These so-called "frankencards" might even swap out the shroud to be from a legitimate card in an extra step to hide it.

Finally, you'll probably notice a fake GPU quite quickly if your card simply doesn't match the performance that you'd expect. If you supposedly bought a 4090 and it's struggling in 4K in a lot of games, that'll instantly be a tell that things may not be as they seem. Also keep an eye out for "too good to be true" deals, like a supposed RTX 4090 for like $200.

As for the reason why they're on the rise, it's fairly simple. With the prohibitive cost of GPUs, people are always on the hunt for a good deal that will give them the ability to play their favorite games in higher definition or with a high refresh rate. These counterfeit GPUs prey on financial hardships that people may be facing; in other words, if the deal is too good to be true, it almost certainly is.