The Mac LC 550 and 575, also sold as the Performa 550 and 575 to the home market, have 4 MB of RAM soldered to the motherboard and a single 72-pin SIMM socket for memory expansion. They can handle up to 36 MB of memory.
1999 – DH writes: I have a Performa 550 (20/160/2x, built in 14″) with a failing hard drive. I also need to replace the keyboard, mouse, and printer.
1998 – DS writes: At our (the Atlanta Mac Users’ Group) annual swap-fest, I was unable to not purchase for a small amount an extremely clean and (I think) handsome LC 550 that had been used by a school administrator. [Readers, you may want to read that again. It’s a masterful use of the double-negative.]