So, an interesting YouTube video, but the $142 is not the whole story here, both in terms of materials and way no in terms of wall clock time required
I appreciate that they did call out the total cost later in the article, along with re-mentioning the specialized tools and experience, but the headline here deserved extra "clickbait alert" call out
Pretty awesome people went to the trouble to do this, casts some light on what is typically darkness on the consumer side of GPU product market segmentation.
Capitalism wins every time.
GPU cores used in these double RAM NVIDIA GPUs are known to have that feature implemented and configurable in signed VBIOS, for some reasons. It only allows single or double RAM configurations as choices, not e.g. 4 separate lines for quadruple RAM, but double configurations can be done with a properly built and assembled PCB if you can source the cores. And there are tons of back alley trained skilled BGA repair specialists in China for mysterious reasons, so that's what they're doing.
If so, I imagine NV "fixed" this oversight with Grace Blackwell -based GPUs (5xxx series). There is too much at stake financially to leave the barn door open.
Could you nvlink several 4090s?
In some countries it is cheaper to repair a phone than to buy a new one. This creates the "back alley trained BGA repair specialists".
When i was first employed in a Eastern Europe country, our computer supplier will "repair" RAM modules this way. Test was simple: insert in PC, see if it boots. It was the only place where i saw Windows 2000 crash more than Windows Me.
Bet the ram size is a compile time constant and therefore you need to get hold of firmware from a card with the amount of ram you intend to add.