Macintosh External Disk Drive

Macintosh External Disk Drive

Developer	Apple Computer
Type	Disk Drive
Release date	May 4, 1984
Introductory price	US$495

The Macintosh External Disk Drive was the original of a series of external 3.5" floppy disk drives manufactured and sold by Apple Computer exclusively for the Macintosh series of computers introduced in January, 1984. Later, Apple would unify their external drives to work cross-platform between the Macintosh and Apple II product lines, dropping the name "Macintosh" from the drives. Though Apple had been producing external floppy disk drives prior to 1984, they were exclusively developed for the Apple II, III and Lisa computers using the industry standard 5.25" flexible disk format. The Macintosh external drives were the first to widely introduce Sony's new 3.5" rigid disk standard commercially and throughout their product line. Apple produced only one external 3.5" drive exclusively for use with the Apple II series called the Apple UniDisk 3.5.

400K

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. The drive case was designed to match the Macintosh and included the same 400K drive installed inside the Macintosh. Although very similar to the 400K drive which newly replaced Apple's ill-fated Twiggy drive in the Lisa, there were subtle differences relating mainly to the eject mechanism. However, all of these drives were labeled confusingly identically. The Macintosh could only support one external drive, limiting the number of floppy disks mounted at once to two. However, 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. The standard formatted capacity of the drive was 360K, however, Apple employed its GCR formatting technique which spun the disk at a different rate on the outer edges to increase the total disk storage. Despite the greater storage capacity, the drive could not be used on the Apple II. Nor could the Lisa accommodate it as an external drive, despite being originally offered with two 871K drives. These drives only support the original Macintosh File System (MFS), though they can be used on any Macintosh which does not also support a SuperDrive (which systems produce a disruptive signal). While 400K disks can be formatted using a Hierarchical File System (HFS) system, they cannot be used as startup disks, or read on an original 128K Macintosh. Unfortunately, when the Macintosh first debuted, a major criticism levied against it was the inadequacy of the single internal floppy disk drive, making the need for two floppy drives a requirement for most purposes. Therefore the external floppy disk drive became critical to the success of the Macintosh.

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 offering in March 1985. However, it was clear that the Mac's original MFS disk formatting system would be inefficient for such a large drive and 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 & 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. However, based on the success of the 3.5" floppy drive for the Mac, there was no such obstacle in immediately implementing the improved capacity Macintosh drive for the Apple II and was introduced in September 1985, four months before the Mac. While simultaneously Apple finally 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.

Apple UniDisk 3.5

In September 1985, Apple released its first 3.5" drive (A2M2053) for the Apple II series utilizing Sony's new 800K drive mechanism which would not be released for the Macintosh until 4 months later. The Apple UniDisk 3.5 drive contained additional circuitry making it an "intelligent" or "smart" drive; this made it incompatible with the Macintosh, despite having the identical drive mechanism that was to be used in the Macintosh. However, with the internal circuit board bypassed or removed (which consisted of its own CPU, RAM and firmware) it will operate as a standard Macintosh 800K drive. This permitted storage hungry Mac users the ability to double their disk capacity 5 months before Apple officially made it available for the Mac. Ironically, though the drive would prove to be significantly faster than the previous 400K drive, it was specifically slowed-down to accommodate the slower 1 MHz processor of the Apple II. It came in the Snow White-styled case and color to match the Apple IIc and had a pass-through connector for the addition of a second daisy-chained drive. It plugged in directly to the Apple IIc (original required a ROM upgrade) and required a specialized interface card on slotted Apple II's, however would later also work directly with the built-in disk port on the Apple IIc Plus and Apple IIGS through backwards compatibility (this was not recommended for the latter two machines due to the drive's slower speed in comparison with the Apple 3.5 Drive). It continued to be sold for use with the Apple IIc and IIe which could not use the subsequent replacement Apple 3.5" drive, until the Apple IIc Plus redesign in 1988 and Apple II 3.5 Disk Controller Card released in 1991. Apple developed a DuoDisk 3.5 which contained two drives vertically stacked, but never brought it to market. The 3.5" format was never very popular in the Apple II community (excluding the 16-bit Apple IIGS) for which most software was released in the 5.25" format to accommodate the existing installed Disk II drives.

Macintosh 800K External Drive

In January, 1986, Apple introduced the Macintosh Plus and a double-sided 800K capacity disk drive, which used the new HFS disk format providing directories and sub-directories. A revised external drive case was produced to accommodate the slimmer 800K disk mechanism. The Macintosh 800K External Drive (M0131) could only be used with Macintosh models except the original 128K, which could not load the new HFS file format required for use with the drive. However, the new drive did support the older 400K single-sided disks allowing them to be shared. Like the 400K drive before it, Apple's GCR formatting allowed for variable speed to accommodate a higher storage capacity than its 720K PC counterparts. In addition, the new Sony mechanism was much quieter and significantly faster than its predecessor. Designed primarily to run on Macs with the new 128K ROM which contained the necessary code to support the drive, it could be used with the older 64K ROMs if the proper software was loaded into the Mac's RAM via the HD20 INIT installed into the system folder. The drive itself controlled its own speed internally and was no longer dependent on an external signal from the Mac, which was blocked on the early drive mechanisms compatible only with the Macintosh. Later universal mechanisms, first used on the Apple II to accommodate proprietary signals, required special cables to isolate the speed signal from the Mac, to prevent damage to the drive. However, with the increased storage capacity combined with 2-4x the available RAM on the Mac Plus, the external drive was less of a necessity than it had been with its predecessors. Nevertheless, with the only option for adding additional storage being extremely expensive hard drives, Apple increased the ability of the Macintosh SE introduced a year later, to access up to 3 floppy drives simultaneously (only one of two Macs to do so).

Apple 3.5" Drive

Beginning in September 1986, Apple adopted a unified cross-platform product strategy essentially eliminating platform specific peripherals where possible. The Apple 3.5" Drive (A9M0106), released in unison with the Apple IIGS computer, replaced the biege-colored Macintosh 800K External Drive with a new 800K external drive that works on both the Apple IIGS as well as the Macintosh. It came in a case similar to the UniDisk, but in Platinum gray. Like the UniDisk 3.5, the Apple 3.5" includes Apple II-specific features such as a daisy-chain connector which allows two drives to be connected to an Apple II computer, and the presence of a manual disk eject button. The Macintosh could still only accommodate one external drive, and ignores the ejection button. But, unlike the Macintosh 800K drive, the Apple 3.5" Drive can be used natively with the 64K ROM stock 128K & 512K without the HD20 INIT, (but only with 400K MFS formatted double-sided, or single-sided disks). Designed as a universal external drive replacement, the Apple 3.5" drive was eventually compatible with the remaining Apple II models in production upon the introduction of the Apple IIc Plus and Apple II 3.5 Disk Controller Card for the Apple IIe.

1.44MB

Following the success of the Macintosh implementation of the 3.5" format, the format was adopted widely by the personal computer industry. However they adopted a different MFM (Modified Frequency Modulation) formatting scheme, incompatible with Apple's own GCR, resulting in a less-expensive drive, but lower 720K capacity. In 1987 a newer and better, MFM-based, "high-density" format was developed which IBM first introduced in their PS/2 systems, doubling the previous storage capacity. In Apple's pursuit of cross-compatibility with DOS & Windows based systems to attract more business customers, they adopted the new format, thus confirming it as the first industry-wide floppy disk standard. However, Apple could not take advantage of the less expensive fixed speed systems of the IBM-based computers, due to its backward incompatibility with their own variable-speed formats.

Apple FDHD Drive

Main article: SuperDrive

Later re-named the Apple SuperDrive (G7287), the Apple FDHD Drive (Floppy Disk High Density) was introduced in 1988 as Apple's first 1.44MB high density double-sided 3.5" floppy disk. It supported all of Apple's 3.5" floppy disk formats as well as all standard PC formats (e.g. MS-DOS, Windows), allowing the Macintosh to read and write all industry standard floppy disk formatting. The external drive was offered only briefly with support for the Apple II, coming late in that product's life. To take advantage of the drive's extended storage and new capabilities, it required the new SWIM (Super Woz Integrated Machine) floppy disk controller chip to be present on the Macintosh and Apple II, the latter requiring the Apple II 3.5 Disk Controller Card which the chip was integrated. If the drive was connected to an older Macintosh, Apple IIGS or Apple IIc Plus with the older IWM (Woz Integrated Machine) chip, the drive would act as a standard 800K drive, without any additional capabilities. The interface card was necessary for the Apple IIGS to make use of its greater storage capacity and ability to handle PC formats. The Apple IIe could not utilize the drive in any form, unless it had the specialized interface card installed, much like the UniDisk 3.5 which the SuperDrive replaced. The last Mac it could be used with was the Classic II and was discontinued shortly thereafter. The drive itself was included internally in every desktop Mac from its introduction until it was eliminated with the introduction of the iMac in 1998.

Macintosh HDI-20 External 1.4MB Floppy Disk Drive

Manufactured exclusively for use with the Macintosh PowerBook line, the Macintosh HDI-20 External 1.44MB Floppy Disk Drive (M8061) contained a low-powered, slimmer version of the SuperDrive and used a small square HDI-20 proprietary connector, rather than the larger standard DE-19 desktop connector, and was powered directly by the laptop. It had a matching dark gray case and an access cover which flipped down to form a stand. The external drive was sold optionally for those PowerBooks which had no built-in drive, however, the identical drive mechanism was included internally in some PowerBook models, which otherwise had no provision to accommodate an external drive. The external case was finally revised in 1997 and renamed Macintosh PowerBook External Floppy Drive, for use exclusively with the PowerBook 2400c, before being discontinued in 1998. This would be the last external floppy drive manufactured by Apple.

See also

• Disk II
• List of Apple drives
• History of the floppy disk
• Timeline of Apple products
• List of products discontinued by Apple Inc.

External links

• vintagemacworld.com Apple External Drives