The Macintosh Hard Disk 20 was the first hard drive developed by Apple Computer specifically for use with the Macintosh 512K. Introduced on September 17, 1985, it was part of Apple's long-awaited solution toward completing the Macintosh Office (a suite of integrated business hardware & software) announced in January 1985. It would be over a year more before Apple would release the file server software AppleShare that would link all of the hardware together. By that time the SCSI interface introduced on the Macintosh Plus in January 1986, would accommodate far faster and more efficient hard drives, rendering the Hard Disk 20 virtually obsolete. Features The Hard Disk 20 (or HD20, as it was known colloquially) contains a 20 MB 3.5" Rodime hard disk which provides over 50 times the data storage of the stock 400 kB disk drive. At the time when the average file size was around 10-20 kB and due to the vast number of those files the HD20 can contain, Apple's original Macintosh File System, which does not allow for directories, made organizing those files unwieldy. Therefore, Apple introduced it with a new System and Finder update which include the Hierarchical File System allowing the user to better organize files on such a large volume. As a result, only the Macintosh 512K can access it; the original Macintosh 128K does not have enough RAM to load the new file system. In fact, even for the Macintosh 512K to use the drive, it requires an additional file in the System Folder on a special startup disk which adds additional code into memory during startup. A startup routine also allows the Mac to check for the presence of a System file on the Hard Disk, switch over to it and eject the startup disk. The HD20 cannot be used as a startup disk directly without first loading the code from the floppy disk drive. With the release of the Macintosh Plus and the Macintosh 512Ke, both containing the upgraded 128 kB ROM which contains the additional code, the HD20 can finally be used alone as a startup disk. While other hard drives were available on the market, Apple's HD20 was generally preferred because it uses the high-speed floppy disk port, whereas third-party drives use the lower-speed Serial Port. While the floppy port was not initially supposed to be used this way, making creative use of the port allows