I took last week off to work on a different project, but I'm back in the Wii U fray now. Long update incoming!
I cut out the SMC and RTC from a WUP-01 motherboard. I was so excited, I forgot to take microscope photos of the bare daughterboard! But here are some pics of the relocation.
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Because I didn't rewire the SMC pins that normally enable the rear USB port protectors, I had to remove them and jumper 5V across the pads.
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Despite taking shortcuts like this, the SMC and RTC still required an annoying amount of wiring. I2C for the SMC, EXI for the RTC, power button, R/B/Y LEDs, and all the GPIOs for the wireless modules. But the relocation worked!
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After this, I spent some time cleaning up and consolidating the wiring and regs in preparation for a preliminary trim.
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I was able to run the 3.3V line from the Pico's onboard regulator, which was convenient. I also moved the Pico to beneath the SOC (not shown).
Next up was the flash memory. Since the eMMC and NAND are tied to the console, you can't use ones from a different motherboard without some dumping/reflashing shenanigans. In other words, the NAND daughterboard must be cut from the same motherboard. This is an irreversible step and must be done at the same time as a mobo trim, which is why I saved this relocation for last.
NAND/eMMC daughterboard...
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...and with wires attached. The eMMC uses 4-bit SDIO (6 wires) and the TSOP NAND uses the same ONFI type interface as the Wii NAND (17 wires).
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Here's the trimmed Wii U motherboard after sanding. Keep in mind this is just a preliminary trim for testing purposes.
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The NAND wiring was tricky. The NAND, eMMC, WiFi module, and even the debug port for the Pico de_Fuse modchip all connect to the same 0.8mm pitch grid of vias under the SOC! I also had to remove the Wifi module and move it to make room for the NAND daughterboard as mentioned previously.
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After reconnecting Wifi and 3.3V/GND:
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The fact that the components are so spread out has actually been a blessing in disguise. It means we can relocate everything with daughterboards instead of expensive custom PCBs. But a FPC for the NANDs, Wifi, and Pico wouldn't be a bad idea.
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It boots! First ever trimmed Wii U! I played some BotW and WWHD, and it's totally stable.
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And finally, a size comparison with a stock mobo. Again, this is just a preliminary trim. Final trim coming soon!
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