A few weeks ago a new prototype DS lite was acquired by ProtonX with help from lasscat. The DS lite is a CPU-X4, which is currently the latest known prototype. The motherboard is almost identical to the retail CPU-01, with the exception of a two curious through holes for a DS phat microphone to be installed. It appears like the microphone hole is on CPU-X3 and may be on CPU-X2B as well, but this is the first time is had been properly documented. The shell uses unreleased colors, has the backwards Nintendo logo, and similar labeling to the CPU-03 proto submitted in
FCC documents. There are also "dev" stickers slapped around the console that suggest it came from Nintendo's
RED, however unlike the shell and board, these may not be genuine. Some have suggested they may have been added by a third party, as so far as we know Nintendo has never used that font on their stickers.
This was also only posted about online by this random Twitter account with 3 tweets only, adding to the suspicious nature of the stickers and console.
Disappointingly this prototype did not have any new firmware/BIOS and was on the latest 2006/03/08 11:19 firmware. The console's SL1 terminal (firmware write protection) has been soldered shut suggesting that someone, either Nintendo or someone else down the line, has updated and overwritten any prototype firmware.
Check out the source for more information as well as full motherboard photos.
Source