A Little Thinking and a Lot of Work Gets Microsoft's Original Xbox Running on Four Times the RAM

Pseudonymous vintage gaming enthusiast "Prehistoricman" has taken Microsoft's original Xbox and give it a major boost in memory — quadrupling the RAM through the use of a clever interposer to adapt modern components for the older motherboard.

"I've been working on this project for two years," Prehistoricman explains by way of background. "This original Xbox is in the first in the world to ever have as much as 256MB of memory. It required many months of reverse engineering, hardware engineering, software hacking, and perseverance. I previously published a mod to upgrade the Xbox 1.6 to 128MB so going for another double was natural."

Microsoft's original Xbox console, named for its use of the DirectX application programming interfaces (APIs) and the fact it's a chunky box, launched in 2001 as the company's entry into the games console market. Powered by a semi-custom Intel Pentium III central processor and an NVIDIA NV2A graphics processor, the console shipped with just 64MB of memory — soldered directly to the motherboard and not user-upgradeable.

Prehistoricman's earlier mod saw the "not user-upgradeable" corrected to "not easily user-upgradeable," taking advantage of the presence of unpopulated RAM chip footprints. Now, though, the tinkerer has delivered another doubling to 256MB — which required some outside-the-box thinking. "[Modern RAM chips] are all BGA [Ball Grid Array," whereas the stock chip is a TQFP, that means it's a thin quad flat pack and it has leads whereas these BGA [parts] do not have leads.

"This is completely a problem, because now we can't just plug it into the Xbox, replacing one chip for [a new] chip of the same size. We need an interposer [to adapt] from that TQFP [footprint] which is on the Xbox motherboard side to the BGA which is on the memory side. So, what I did was put together this PCB in KiCad. It looks pretty complicated, but really this is basically just plumbing."

The interposer PCB routes signals from the BGA memory chips to their equivalent pins on a TFQP package, using a hybrid flexible PCB substrate to minimize thickness. While that's enough to get the memory chips running — when coupled with modified software capable of recognizing and initializing the additional RAM — it could also be the source of some memory clocking issues Prehistoricman encountered, owing to changes in the trace lengths between the memory controller and the new chips.

The project is documented in full in the video embedded above and on Prehistoricman's YouTube channel; a second video by monomymous YouTuber Tito demonstrates the installation process.