The upgraded version of the Super FX Patch, this is the Super FX Development Kit!
Unlike the old version, this one aside activating the chip, it contains routines already ported to Super FX that gives the game a boost, it also makes it easier to create routines for it.
This patch heavily modifies the SMW engine so this can have incompatibilities. However, it also remaps several addresses, in which have been fixed in the newest LM update. Make sure to check the readme for more details!
In accurate, cycle-based rendering emulators, it seems to cause flickering line problems in the presence of windowing HDMA, especially during windowing HDMA fades (ellipses, overworld transitions, etc). Messageboxes seem to be fine. Very notable in the title screen as well as transitioning from Yoshi's Island to the main overworld.
I was reading on the SD2SNES Ikari forums and they said that SA-1 support may be harder to do than Super FX. So we might see Super FX before SA-1 on real hardware. So this patch might come in handy in the future.