Hard Disk 20
Connects to | Macintosh Plus; Macintosh 512K via:
|
---|---|
Design firm | Hard Disk |
Memory | 20 MB |
Connection | Floppy drive port at 500 kbit/s[1][2] |
Power consumption | 30 W |
Weight | 7 lbs (3.2 kg) |
Dimensions | 3.1 x 9.7 x 10.5 inches (7.9 x 25 x 27 cm) |
The Macintosh Hard Disk 20 is the first
Features
The Hard Disk 20 (or HD20, as it was known colloquially) contains a 20 MB 3.5"
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
Specifications
Source:[5]
- Recording Surfaces: 2
- Per Drive: 20.7 MB (formatted)
- No. of Cylinders: 610
- Total No. of Tracks: 1220
- No. of Sector/Track: 32
- Bytes/Sector: 532 (formatted)
- Total No. of Blocks (Data): 38,964
- Spare Blocks: 76
- Access Time: Track to Track 10 ms; Average 50 ms; Maximum 150 ms; Average Latency 10.9 ms
- Rotational Speed: the drive has a rotational speed of 45.73 rotations/second (2744 rpm) and access time of 85 ms.[2]
History
In 1985, the HD20 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 20SC, the first SCSI drive they manufactured, the HD20 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 HD20's unique design and position in the marketplace was quickly outmoded by the advancement of the significantly faster SCSI standard which 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.[6] Apple officially dropped support for the HD20 with System 6 as well as omitting the necessary ROM code beginning with the Macintosh II.[7] Sales of the HD20 continued to support the Macintosh 512Ke which has no other hard drive options, until it was discontinued in late 1987. Apple dropped support for the HD20 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, are able to continue to use the older slower technology.
Manufactured in significant numbers for almost two years, the HD20 remains as one of the few surviving hard drives usable by a stock Macintosh 512K or 512Ke.
See also
References
- ^ "The Mac Plus 30 Years On". January 24, 2016. Archived from the original on April 25, 2016. Retrieved April 20, 2016.
- ^ a b "Apple brand HD20, HD20 SC Info". 2010. Archived from the original on February 3, 2016. Retrieved April 20, 2016.
- ^ "Macintosh 128K and 512K: SCSI Hard Drives". Archived from the original on September 27, 2022. Retrieved April 22, 2015.
- ^ Lewis, Peter H (October 8, 1985). "Peripherals; Apple gives its Macintosh a hard disk". New York Times. Archived from the original on September 27, 2022. Retrieved December 30, 2007.
- ^ Dog Cow (October 24, 2017). "Macintosh Hard Disk 20". Mac GUI. Archived from the original on March 6, 2021. Retrieved October 10, 2021.
- ^ "Apple HD-20: How To Convert It Into A SCSI Device". Archived from the original on January 11, 2014. Retrieved January 11, 2014.
- ^ "System 6.0.3: Incompatible with Macintosh 512Ke and HD20". Archived from the original on January 11, 2014. Retrieved January 11, 2014.
External links
- Hard Disk 20 technical specifications at apple.com at the Wayback Machine (archived May 16, 2011)
- 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 at the Wayback Machine (archived February 20, 2007)
- The M0001 Registry Owners of Vintage Macintosh
- Apple Macintosh Before System 7