The drive was still completely incompatible with PC drives. The new drive was controlled by the same IWM chip as in previous models, implementing variable speed GCR. It had a new 3.5-inch double-sided 800 KB floppy drive, offering double the capacity of previous Macs along with backward compatibility.

The Macintosh Plus was the last classic Mac to have a phone cord-like port in front for the keyboard, as well as the DE-9 connector for the mouse later models would use ADB ports. SCSI ports remained standard equipment for all Macs until the introduction of the iMac in 1998. As the Mac Plus had no provision at all for expansion other than the SCSI bus, the entire onus of expansion was on the user. Its SCSI implementation was engineered shortly before the initial SCSI spec was finalized and, as such, is not 100% SCSI-compliant. The Mac Plus was the first Macintosh model to include a SCSI port, which launched the popularity of external SCSI devices for Macs, including hard disks, tape drives, CD-ROM drives, printers, and even monitors. It originally had the same generally beige-colored case as the original Macintosh ('Pantone 453'), but in 1987, the case color was changed to the long-lived, warm gray 'Platinum' color. As an evolutionary improvement over the 512K, it introduced RAM expansion from 1 MiB to 4 MiB, and the SCSI peripheral bus, among smaller improvements. The Macintosh Plus computer was the third model in the Macintosh line, introduced two years after the original Macintosh and a little more than a year after the Macintosh 512K.

How to use a mac plus computer