You’ve probably heard whispers about those crazy "Frankenstein" GeForce RTX 4090 48GB graphics cards coming out of China. Now, a Russian PC technician and builder known as VIK-on has pulled back the curtain, giving us a detailed look at how these gaming flagships are being transformed to double their VRAM, specifically for highly sought-after AI workloads.
The standard GeForce RTX 4090 is built as a mainstream product and, unlike Nvidia’s professional and data center cards, does not support a clamshell memory configuration. This means the Ada Lovelace flagship only houses memory chips on one side of its PCB. To get around this, Chinese factories have created a "GeForce RTX 4090 48GB upgrade kit" that sells for around $142 in China.
The DIY Upgrade Process
The upgrade kit includes a custom PCB designed with a clamshell configuration, allowing for the installation of twice the number of memory chips on both sides. Most of the components are pre-installed, but the user must solder the GPU and memory chips onto the new PCB. The kit even comes with a blower-style cooling solution, designed for integration with multi-GPU architectures commonly found in workstations and servers.
In a demonstration, VIK-on showed the process of carefully extracting the AD102 silicon and twelve 2GB GDDR6X memory chips from an MSI GeForce RTX 4090 Suprim. He then installed them onto the barebone PCB, using spare memory chips from defective graphics cards to get the additional GDDR6X modules at no extra cost. This is a highly technical operation that requires specialized soldering skills and access to high-end tools.
The Firmware and Financials
After the hardware is in place, the technician uploads a modified firmware onto the new GeForce RTX 4090 48GB. Since each graphics card has a unique GPU device ID, the hacked firmware is necessary to trick the system into recognizing the expanded memory capacity. This kind of firmware mod has been present for some time, with enthusiasts discovering it during the RTX 20-series era. While originally used to salvage cards with defective memory channels, modders later realized they could also use it to expand memory capacity.
Upgrading the GeForce RTX 4090 to 48GB is a costly endeavor. In addition to the graphics card itself, the spare memory modules cost around $24 each on Chinese e-commerce platforms, bringing the total cost of the upgrade to about $430. Assuming you bought your RTX 4090 at its original MSRP of $1,599, the total cost for your newly upgraded card would be around $2,029. With these 48GB graphics cards typically selling for around $3,320 in China, a DIY enthusiast can save close to 39% by performing the upgrade themselves.
Given that RTX 4090 supply is already starting to dwindle, it’s only a matter of time before these factories begin experimenting with the upcoming GeForce RTX 5090. A rumor is already circulating about a GeForce RTX 5090 with 128GB of memory, proving that when there’s a demand, the modding community will find a way.
