Microtech Macintosh Peripherals Double Sided 800K External Drive Teardown For Restoration
2Microtech Macintosh Peripherals Double Sided 800K External Drive Teardown For Restoration
In 1986, the Macintosh Plus Disk Drive Kit (P/N M2516) upgraded a 128K or 512K Macintosh with the 800K double-sided drive and the 128K ROM. It cost $299, which included dealer installation and a Macintosh Plus System Tools Disk. An included manual, Macintosh Plus Internal Disk Drive, explained the new features present in the Macintosh Plus Finder as well as the new HFS, and the differences between single- and double-sided disks.
The original Macintosh External Disk Drive (M0130) was introduced with the Macintosh on January 24, 1984. However, it did not actually ship until May 4, 1984, sixty days after Apple had promised it to dealers. Bill Fernandez was the project manager who oversaw the design and production of the drive.[1] The drive case was designed to match the Macintosh and included the same 400-kilobyte drive (a Sony-made 3 1⁄2-inch single-sided mechanism) installed inside the Macintosh. Although very similar to the 400-kilobyte drive which newly replaced Apple's ill-fated Twiggy drive in the Lisa, there were subtle differences relating mainly to the eject mechanism. However, confusingly all of these drives were labelled identically. The Macintosh could only support one external drive, limiting the number of floppy disks mounted at once to two, but both Apple and third party manufacturers developed external hard drives that connected to the Mac's floppy disk port, which had pass-through ports to accommodate daisy-chaining the external disk drive. Apple's Hard Disk 20 could accommodate an additional daisy-chained hard drive as well as an external floppy disk.
3.5-inch single-sided floppies had been used on several microcomputers and synthesizers in the early 1980s, including the Hewlett Packard 150 and various MSX computers. The standard on all of these was MFM with 80 tracks and 9 sectors per track, giving 360 kB per disk. However, Apple's custom interface used Group Coded Recording (GCR) and a unique format which put fewer sectors on the smaller inner tracks and more sectors on the wider outer tracks of the disk. The disk would speed up when accessing the inner tracks and slow down when accessing the outer ones. This allowed more space per disk (400 kB) and also improved reliability by reducing the number of sectors on the inner tracks which had less physical media to allocate to each sector.
The external 400-kilobyte Macintosh drive will work on any Macintosh that does not have a high density SuperDrive controller (due to electrical changes with the interface), but the disks in practice only support the MFS file system. Although a 400-kilobyte disk may be formatted with HFS, it cannot be booted from, nor is it readable in a Mac 128/512.
Copy protection schemes were not as elaborate or widespread on Macintosh software as they were on Apple II software for several reasons. First, the Mac drives did not afford the same degree of low-level control. Also Apple did not publish source listings for the Mac OS ROMs as they did with the Apple II. Finally, the Mac OS routines were considerably more complex and disk access had to be synchronized with the mouse and keyboard.
800K
By early 1985, it was clear that the Macintosh needed additional storage space, in particular a hard drive. Apple announced their first hard drive for the Mac in March 1985. However, the MFS file system did not support subdirectories, making it unsuitable for a hard disk. Apple quickly began adopting for the Mac the hierarchical based SOS filing system introduced with the Apple III and long since implemented in ProDOS for the Apple II series and the Lisa. This change in the Mac's filing system delayed the introduction of the double sided Sony drives which Apple intended to offer as soon as the technology was available, a concession they made when adopting the Sony drives over their own problematic double-capacity Twiggy drives.[2][3] However, based on the success of the 3.5-inch floppy drive for the Mac, there was no such obstacle in immediately implementing an 800-kilobyte drive for the Apple II, so it was introduced in September 1985, four months before the version for the Mac. While Apple simultaneously introduced their new hard drive after a 6-month delay, they chose not to implement the new floppy drive for the Macintosh at that time.
The Apple External 800K Drive sold for $499, and required the new 128K ROM or the Hard Disk 20 file.