here is a list of all (rare) MCPX ic I know off:
MCP X-mode 2
MCP X2 (DVT3)
MCPX X2 (found in DVT4 and Sega Chihiro)
MCPX X3
MCPX X3P (not sure, but my latest notes state I found some info on this
N64freak picture, repairing a Sega Chihiro (google this if you think "sega?")
N64 Freak in this thread on Assemblergames has also did some amazing soldering things :https://assemblergames.com/threads/what-is-the-diference-between-the-mcpx-chips-big-images.41069/#post-952246
[EDIT} from N64freak I now understand the SMC might not need to be swapped, so you can ignore the rest of this post below. From various sources I know that if you would replace a X3 with a X2, you should swap the SMC ic to a matching set aswell (so just ordering X2 from china doesnt work?) I dont know if an MCP X2 is requireing its own SMC against X2. Those are even more rare, All retail have some kind of X3, but revisions where made. altho MS did a big fix and forced Nvidia to scap alott of mcpx, Nvidia disliked Microsoft verymuch after that. so MS couldnt that easely make newer Silicon designs after the 1.6 design.