NVIDIA GeForce RTX 3070 Memory-Modded with 16GB | TechPowerUp
 
PC enthusiast and overclocker VIK-on pulled off a daring memory chip mod on his Palit GeForce RTX 3070 GamingPro OC graphics card, swapping its 8 GB of 14 Gbps GDDR6 memory with 16 GB of it, using eight replacement 16 Gbit chips. The modded card is able to recognize the 16 GB of memory, is able to utilize it like other 16 GB graphics cards (such as the Radeon RX 6800), and is fairly stable with benchmarks and stress tests, although not initially stable. It did spring up some black-screens. VIK-on later discovered that locking the clock-speeds using EVGA Precision-X stabilizes the card, so it performs as expected.

The mod involves a physical replacement of the card's stock 8 Gbit memory chips with 16 Gbit ones; and shorting certain straps on the PCB that let it recognize the desired memory chip brand and density. After the mod, the GeForce driver and GPU-Z are able to read 16 GB of video memory, and the card is able to handle stress tests such as FurMark. The card was initially underperforming in 3DMark, putting out a TimeSpy score of just 8356 points; but following the clock-speed lock fix, is able to score around 13000 points. The video presentation can be watched from the source link below. Kudos to VIK-on!
 
Amazing work and it is a bit funny that EVGA Precision X stabilized the card. 

Interesting but not even remotely practical or possible for 99.999% of users.