A hardware hacker has equipped a Raspberry Pi 400 with twice as much RAM. Built into a keyboard, the Pi has 4GB of onboard memory, but Reddit user Pi-800 doubled that by transplanting the 8GB chip from a Compute Module.
The tweaker has posted details about his project on Reddit. He used the memory of a Raspberry Pi Compute Model 4, which comes with 8GB of ram. He saw that the circuits for the ram chip in both Pis were identical. He managed to remove the memory from one Pi and place it on the other board. The chips are attached with small solder balls, which had to be replaced before the transplant. The painstaking work was therefore mainly in the fact that the user had to replace all the solder balls from the ball grid array or bga by hand. That is two hundred, which have a diameter of 0.3 mm. The tinkerer used hot air to solder or reflow the chip onto the pcb with those balls.
The long work was ultimately successful. Pi800 shows screenshots showing that the Pi 400 does indeed have 8GB of ram and can also run on a 64bit version of Raspberry Pi OS. “Now we can call it the Pi 800,” the hacker says in his post. The hacker says it probably won’t be possible to upgrade to 16GB, although the Pi 400’s CPU supports it. This is because a 16GB ram chip needs more contact points, so that it does not fit on the existing pcb.