A Chinese hardware repair YouTuber received four allegedly faulty RTX 4090 graphics cards that needed repairing. The YouTuber discovered that three of the four cards were fake graphics cards modded from RTX 3090s and RTX 3080s to look like the real deal. The three fake cards had to be scrapped since they were apparently incapable of running. The customer of the four GPUs apparently paid $1,394 (10,000 yuan) for each GPU and purchased all four from an overseas vendor or supplier.
The Chinese repair YouTuber shared key insights to detect fake RTX 4090s. For starters, the QR code on every legitimate RTX 4090 is located on the very bottom left corner of the GPU substrate. On legitimate RTX 3090s and RTX 3080s, the QR code is located in the same area but slightly above the bottom left corner of the substrate. Most modders will allegedly not move the QR code of a GPU die they are trying to make look like another one, making this an easy way to verify whether an RTX 4090 is real.
the next level of the 4090 scam.according to 张哥,this time the surrounding mlcc position is correct, the qr code position is also correct.however the color of the PCB substrate is too fake, and the metal frame on the substrate is not fully attached.bilibili 修电脑的张哥… pic.twitter.com/tnQMBs8zOeJune 14, 2025
Additionally, RTX 30 series GPUs have a capacitor on the top right of the substrate that allegedly protrudes up a little bit; by contrast, the RTX 4090 does not.
As previously mentioned, three of the four RTX 4090s were faulty, featuring RTX 30 series GPU dies with modified laser engravings designed to deceive users into believing they were genuine RTX 4090s. The first one featured a QR code in the wrong area and fake VRAM, according to the YouTuber. The second GPU sported a scarred "AD102" die with the same QR code issue as the first card. The third GPU was by far the worst, sporting an abnormal green substrate and a substrate plate that was skinnier than the same plate on a real RTX 4090. The substrate plate was in such bad shape that the frame wasn't fully seated onto the substrate itself.
Only one of the RTX 4090s was real, featuring legitimate damage that needed to be fixed. The YouTuber discovered that some of the GDDR6X chips and some of the capacitors on the back of the board were bad. After replacing two of the faulty GDDR6X chips with new ones and fixing the rear capacitors, the card sprang to life and ran stably with no issues.
Selling counterfeit RTX 4090 graphics cards is sadly a common practice in today's GPU market. Thanks to the incredible value and high demand of Nvidia's previous-gen flagship, criminals can profit from stripping an old RTX 30-series graphics card and modifying it to look like an RTX 4090. Nvidia's Ampere-based GA102 die and memory configuration are similar enough to those of the AD102 GPUs that it can be easy to fake one to look like the other. However, it doesn't always have to be a GA102 chip; scams have also been seen where an RTX 4080 is falsely listed as an RTX 4090.
Thankfully, there have not been any major reports of fake RTX 5090s in the wild. But with how high the demand and how expensive the RTX 5090 is, it seems inevitable that modders will figure out how to sell fake RTX 5090s in the future as well.
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