Hard Disk 20
Encyclopedia
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. Unfortunately 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.
hard disk
which provided over 50 times the data storage of the stock 400K disk drive. At a time when the average file size was around 10-20K and due to the vast number of those files the HD 20 could contain, Apple's original Macintosh File System
, which did not allow for directories, would have made organizing those files unwieldy. Therefore Apple introduced it with a new System and Finder update which included the brand new Hierarchical File System
allowing the user to better organize files on such a large volume. As a result only the Macintosh 512K
could access it; the original Macintosh 128K
did not have enough RAM
to load the new file system. In fact, even for the Macintosh 512K to use the drive, it required an additional file in the System Folder on a special startup disk which added additional code into memory during startup. An ingenious startup routine also allowed the Mac to check for the presence of a System file on the Hard Disk, switch over to it and eject the startup disk. Unfortunately, the HD 20 could not 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 128K ROM
which contained the additional code, the HD 20 could finally be used alone as a startup disk.
While other hard drives were available on the market, Apple's HD 20 was generally preferred mainly because Apple broke their own development rules when they offered it. Originally the Macintosh was designed with two serial port
s which were to meet all the expansion needs of the user. It also included a dedicated floppy disk port for one external floppy disk. Most of the hard drives which were available on the market used the slower serial port
to transfer data per Apple's specifications. Apple instead engineered the HD 20 to use the faster floppy disk port, enabling the user to daisy-chain an external floppy disk drive as well as an additional HD 20. With few exceptions, this along with complete compatibility with the new Hierarchical File System
, gave Apple an instant edge over the competition. In addition, the HD 20 had a convenient "zero-footprint" design which fit precisely underneath the Macintosh, merely elevating it 3 inches, but otherwise taking up no more desk-space.
, the first SCSI drive they manufactured, the HD 20 was the only Apple-manufactured hard drive available for any Macintosh except the Macintosh XL
. The HD20 was not compatible with any other Apple computer or other platforms.
However, the HD 20's unique design and position in the marketplace, was quickly outmoded by the advancement of the significantly faster SCSI
standard which also debuted with the Macintosh Plus in January 1986. Some third party companies offered a SCSI
conversion kit which replaced the controller board thus preserving the user's investment in the expensive but proprietary Rodime drive. Apple officially dropped support for the HD 20 with System 6
as well as omitting the necessary ROM code beginning with the Macintosh SE/30
. Sales of the HD 20 continued to support the Macintosh 512Ke which had no other hard drive options until it was discontinued in late 1987. Apple quickly dropped support for the HD 20 in all of its newer Macs, only to find many business users upgrading their older systems needed a way to transfer data from the unsupported drives to the newer Macs. Only Macs with legacy technology and floppy disk ports, which were eliminated entirely from Macintosh computers in 1991, were able to continue to use the older slower technology.
Manufactured in significant numbers for almost two years, The HD 20 remains as one of the few surviving hard drives a stock Macintosh 512K or 512Ke can use.
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
specifically for use with the Macintosh 512K
Macintosh 512K
The Macintosh 512K Personal Computer, also known as the "Fat Mac", is the second of a long line of Apple Macintosh computers, was the first update to the original Macintosh 128K. It was virtually identical to the previous Mac, differing primarily in the amount of built-in memory , which quadrupled...
. Introduced on September 17, 1985, it was part of Apple's long awaited solution toward completing the Macintosh Office
Macintosh Office
The Macintosh Office was Apple's third failed attempt to enter into the business environment as a serious competitor to IBM. Consisting of three key parts, a network file server, local area network and a network Laser printer, Apple announced Macintosh Office in January 1985 with an ill-fated,...
(a suite of integrated business hardware & software) announced in January 1985. Unfortunately it would be over a year more before Apple would release the file server software AppleShare
AppleShare
AppleShare was a product from Apple Computer which implemented various network services. Its main purpose was acting as a file server, using the AFP protocol...
that would link all of the hardware together. By that time the SCSI
SCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
interface introduced on the Macintosh Plus
Macintosh Plus
The Macintosh Plus computer was the third model in the Macintosh line, introduced on January 16, 1986, two years after the original Macintosh and a little more than a year after the Macintosh 512K, with a price tag of US$2599...
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) contained a 20MB 3.5" RodimeRodime
Rodime was an electronics company specialising in hard disks, based in Glenrothes, Scotland. It was founded in 1979 by several Scottish and American former employees of Burroughs Corporation and listed on the London Stock Exchange in 1986, becoming Rodime PLC....
hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
which provided over 50 times the data storage of the stock 400K disk drive. At a time when the average file size was around 10-20K and due to the vast number of those files the HD 20 could contain, Apple's original Macintosh File System
Macintosh File System
Macintosh File System is a volume format created by Apple Computer for storing files on 400K floppy disks. MFS was introduced with the Macintosh 128K in January 1984....
, which did not allow for directories, would have made organizing those files unwieldy. Therefore Apple introduced it with a new System and Finder update which included the brand new Hierarchical File System
Hierarchical File System
Hierarchical File System is a file system developed by Apple Inc. for use in computer systems running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs...
allowing the user to better organize files on such a large volume. As a result only the Macintosh 512K
Macintosh 512K
The Macintosh 512K Personal Computer, also known as the "Fat Mac", is the second of a long line of Apple Macintosh computers, was the first update to the original Macintosh 128K. It was virtually identical to the previous Mac, differing primarily in the amount of built-in memory , which quadrupled...
could access it; the original Macintosh 128K
Macintosh 128K
The Macintosh 128K machine, released as the "Apple Macintosh", was the original Apple Macintosh personal computer. Its beige case contained a monitor and came with a keyboard and mouse. An indentation in the top of the case made it easier for the computer to be lifted and carried. It had a selling...
did not have enough RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
to load the new file system. In fact, even for the Macintosh 512K to use the drive, it required an additional file in the System Folder on a special startup disk which added additional code into memory during startup. An ingenious startup routine also allowed the Mac to check for the presence of a System file on the Hard Disk, switch over to it and eject the startup disk. Unfortunately, the HD 20 could not be used as a startup disk directly without first loading the code from the floppy disk drive. With the release of the Macintosh Plus
Macintosh Plus
The Macintosh Plus computer was the third model in the Macintosh line, introduced on January 16, 1986, two years after the original Macintosh and a little more than a year after the Macintosh 512K, with a price tag of US$2599...
and the Macintosh 512Ke
Macintosh 512Ke
The Macintosh 512K enhanced was introduced in April 1986 as a cheaper alternative to the top-of-the-line Macintosh Plus, which had debuted three months previously. It was the same as the Macintosh 512K but with the 800K disk drive and 128K of ROM used in the Macintosh Plus. Like its predecessors,...
, both containing the upgraded 128K ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
which contained the additional code, the HD 20 could finally be used alone as a startup disk.
While other hard drives were available on the market, Apple's HD 20 was generally preferred mainly because Apple broke their own development rules when they offered it. Originally the Macintosh was designed with two serial port
Serial port
In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...
s which were to meet all the expansion needs of the user. It also included a dedicated floppy disk port for one external floppy disk. Most of the hard drives which were available on the market used the slower serial port
Serial port
In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...
to transfer data per Apple's specifications. Apple instead engineered the HD 20 to use the faster floppy disk port, enabling the user to daisy-chain an external floppy disk drive as well as an additional HD 20. With few exceptions, this along with complete compatibility with the new Hierarchical File System
Hierarchical File System
Hierarchical File System is a file system developed by Apple Inc. for use in computer systems running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs...
, gave Apple an instant edge over the competition. In addition, the HD 20 had a convenient "zero-footprint" design which fit precisely underneath the Macintosh, merely elevating it 3 inches, but otherwise taking up no more desk-space.
History
In 1985, the HD 20 was an important step to solidifying the Macintosh as a true business computer and it was eagerly anticipated following its April announcement. Until Apple's introduction a year later of the Hard Disk 20SCHard Disk 20SC
The Apple Hard Disk 20SC was Apple's first SCSI based hard drive for the Apple II family as well as the Macintosh and other third party computers using an industry standard SCSI interface.-History:Released...
, the first SCSI drive they manufactured, the HD 20 was the only Apple-manufactured hard drive available for any Macintosh except the Macintosh XL
Macintosh XL
Macintosh XL was a modified version of the Apple Lisa personal computer made by Apple Computer, Inc. In the Macintosh XL configuration, the computer shipped with MacWorks XL, a Lisa program that allowed 64 K Macintosh ROM emulation...
. The HD20 was not compatible with any other Apple computer or other platforms.
However, the HD 20's unique design and position in the marketplace, was quickly outmoded by the advancement of the significantly faster SCSI
SCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
standard which also debuted with the Macintosh Plus in January 1986. Some third party companies offered a SCSI
SCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
conversion kit which replaced the controller board thus preserving the user's investment in the expensive but proprietary Rodime drive. Apple officially dropped support for the HD 20 with System 6
System 6
System 6 is a graphical user interface-based operating system for Macintosh computers. It was released in 1988 by Apple Computer and was part of the Mac OS line of operating systems. System 6 was shipped with various Macintosh computers until it was succeeded by System 7 in 1991. The boxed...
as well as omitting the necessary ROM code beginning with the Macintosh SE/30
Macintosh SE/30
The Macintosh SE/30 is a personal computer that was designed, manufactured and sold by Apple Computer, Inc. from 1989 until 1991. It was the fastest and most expandable of the original black-and-white compact Macintosh series....
. Sales of the HD 20 continued to support the Macintosh 512Ke which had no other hard drive options until it was discontinued in late 1987. Apple quickly dropped support for the HD 20 in all of its newer Macs, only to find many business users upgrading their older systems needed a way to transfer data from the unsupported drives to the newer Macs. Only Macs with legacy technology and floppy disk ports, which were eliminated entirely from Macintosh computers in 1991, were able to continue to use the older slower technology.
Manufactured in significant numbers for almost two years, The HD 20 remains as one of the few surviving hard drives a stock Macintosh 512K or 512Ke can use.
External links
- Hard Disk 20 technical specifications at apple.com
- Mac Systems Compatible with Hard Disk 20 at apple.com
- Hard Disk 20 tutorial at VintageMacWorld.com
- Hard Disk 20 Info at Mac512.com's Classic Macintosh Preservation area
- The M0001 Registry Owners of Vintage Macintosh
- Apple Macintosh Before System 7