"Following the release of the original Macintosh in 1984 and the Macintosh 512K in 1985, Apple released the Macintosh Plus in 1986, now with 1 MB of RAM, an 800 kB 3.5" floppy disk drive, and a SCSI port. Let's check it out."
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips