Late in the product life of the Lisa, there were third-party hard disk drives, SCSI controllers, and double-sided 3.5-inch floppy-disk upgrades. Unlike the original Macintosh, the Lisa has expansion slots. The Lisa 2 motherboard has a very basic backplane with virtually no electronic components, but plenty of edge connector sockets and slots. There are two RAM slots, one CPU upgrade slot, and one I/O slot all in parallel placement to each other. At the other end, there are three "Lisa" slots in parallel.