According to a poster on TV Tropes:
CPU: IBM PowerPC 7xx-based tri-core processor “Espresso” clocked at 1.24 GHz before the 3.0.0 update, 3.24 GHz after the 3.0.0 update. This is an evolution to the Broadway chip used in the Wii, is 64 bit and uses Power6 technote When IBM has said that Nintendo has licensed the Power7 tech from IBM, Nintendo is not using it for the Wii U, explaining its backwards compatibility.
GPU: AMD Radeon High Definition processor codenamed “Latte” with an eDRAM cache built onto the die clocked at 550 MHz before the 3.0.0 update, 800 MHz after the 3.0.0 update.
This sounds wildly improbable to me, but it’s an intriguing idea nonetheless. Is it possible that Nintendo is trying to use firmware patches to make the Wii U more powerful?