not that it matters,  i just would like to throw in that i really like the LC520 / LC550 Main-boards,  just as i like the LCIII  And pretty much all LC-III's will run at 33mhz no problem.     -- And to go long with the color classic.    Slapping a LC520/LC550 in there, Brings that machine A L I V E! and there is no Mod's, its just a slide in,  Pop rear I/O cover back on and run.