RK05
Encyclopedia
The RK05 DECpack was a moving head magnetic disk drive manufactured by the Digital Equipment Corporation
of Maynard
, Massachusetts
. It stored approximately 2.5 MB
on a 14", single-platter IBM
-2315-style front-loading removable disk cartridge. The cartridge permitted users to have relatively unlimited off-line storage and to have very fast access to such data. At the time DEC had numerous operating systems for each computer architecture so operating systems could also be changed quickly. The RK05 was the disk successor to DECtape
for personal, portable, and expandable storage. While the smallest practical configuration was two drives, many systems had four or more drives.
Occupying 10.5 inches of space in a standard 19 inch computer rack, the drive was competitive at the time. The cartridge contained a single, 14" aluminum
platter coated with iron oxide
in an epoxy binder. The two ferrite
and ceramic
read/write head
s were pressed towards the disk by spring arms, floating on an air bearing
maintained by the rotation of the disk. They were positioned by a voice coil
actuator using a linear optical encoder
for feedback. The track density was 100 tracks-per-inch. The bit density along the track was about 2200 bits-per-inch. Discrete electronics computed the velocity profile for seeks commanded by the controller. An absolute filter (HEPA filter
) provided pressurized air to the cartridge, excluding most contaminants that would otherwise cause head crash
es.
When used on 16-bit systems such as the PDP-11
, the drive stored roughly 1.2 megawords. When used on 12-bit systems such as the PDP-8
, the drive stored 1.6 megawords (so roughly the same bit capacity, albeit formatted differently). Multiple drives were daisy chain
ed from their controller using Unibus
cabling; a terminator was installed in the farthest drive.
The 16-bit (Unibus) controller was known as the RK11; it allowed the connection of up to eight RK05 drives. Seeks could be overlapped among the drives but only one drive at a time could transfer data.
The most-common 12-bit (Omnibus) controller was known as the RK8E; it supported up to four RK05 drives. The RK05 disk had more than 4096 sectors and so could not be addressed completely by a single PDP-8 12-bit word. To accommodate this, the OS/8
operating system split each drive into two logical volumes, for example, RKA0 and RKB0, representing the outermost and innermost cylinders of the drive.
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
of Maynard
Maynard, Massachusetts
Maynard is a town in Middlesex County, Massachusetts, United States. As of the 2010 census, the town population was 10,106.- History :Maynard, located on the Assabet River, was incorporated as an independent municipality in 1871. Prior to that it was known as 'Assabet Village' but was legally...
, Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
. It stored approximately 2.5 MB
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
on a 14", single-platter IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
-2315-style front-loading removable disk cartridge. The cartridge permitted users to have relatively unlimited off-line storage and to have very fast access to such data. At the time DEC had numerous operating systems for each computer architecture so operating systems could also be changed quickly. The RK05 was the disk successor to DECtape
DECtape
DECtape, originally called "Microtape", was a magnetic tape data storage medium used with many Digital Equipment Corporation computers, including the PDP-6, PDP-8, LINC-8, PDP-10, PDP-11, PDP-12, and the PDP-15. On DEC's 32-bit systems, VAX/VMS support for it was implemented but did not become an...
for personal, portable, and expandable storage. While the smallest practical configuration was two drives, many systems had four or more drives.
Occupying 10.5 inches of space in a standard 19 inch computer rack, the drive was competitive at the time. The cartridge contained a single, 14" aluminum
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
platter coated with iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...
in an epoxy binder. The two ferrite
Ferrite (magnet)
Ferrites are chemical compounds consisting of ceramic materials with iron oxide as their principal component. Many of them are magnetic materials and they are used to make permanent magnets, ferrite cores for transformers, and in various other applications.Many ferrites are spinels with the...
and ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
read/write head
Disk read-and-write head
Disk read/write heads are the small parts of a disk drive, that move above the disk platter and transform platter's magnetic field into electrical current or vice versa – transform electrical current into magnetic field...
s were pressed towards the disk by spring arms, floating on an air bearing
Fluid bearing
Fluid bearings are bearings which support the bearing's loads solely on a thin layer of liquid or gas.They can be broadly classified as fluid dynamic bearings or hydrostatic bearings. Hydrostatic bearings are externally pressurized fluid bearings, where the fluid is usually oil, water or air, and...
maintained by the rotation of the disk. They were positioned by a voice coil
Voice coil
A voice coil is the coil of wire attached to the apex of a loudspeaker cone. It provides the motive force to the cone by the reaction of a magnetic field to the current passing through it...
actuator using a linear optical encoder
Encoder
An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.-Media:...
for feedback. The track density was 100 tracks-per-inch. The bit density along the track was about 2200 bits-per-inch. Discrete electronics computed the velocity profile for seeks commanded by the controller. An absolute filter (HEPA filter
HEPA
High-Efficiency Particulate Air or HEPA is a type of air filter. Filters that are awarded the HEPA accolade are used in various locations, whether in medical facilities, automotive vehicles, airplanes, home filters, or wherever very pure air is sought. The filter must satisfy certain standards of...
) provided pressurized air to the cartridge, excluding most contaminants that would otherwise cause head crash
Head crash
A head crash is a hard-disk failure that occurs when a read–write head of a hard disk drive comes in contact with its rotating platter, resulting in permanent and usually irreparable damage to the magnetic media on the platter surface....
es.
When used on 16-bit systems such as the PDP-11
PDP-11
The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...
, the drive stored roughly 1.2 megawords. When used on 12-bit systems such as the PDP-8
PDP-8
The 12-bit PDP-8 was the first successful commercial minicomputer, produced by Digital Equipment Corporation in the 1960s. DEC introduced it on 22 March 1965, and sold more than 50,000 systems, the most of any computer up to that date. It was the first widely sold computer in the DEC PDP series of...
, the drive stored 1.6 megawords (so roughly the same bit capacity, albeit formatted differently). Multiple drives were daisy chain
Daisy chain
Daisy chain may refer to a daisy garland created from daisy flowers, the original meaning and the one from which the following derive by analogy:*Daisy chain *Daisy chain *Daisy chain...
ed from their controller using Unibus
Unibus
The Unibus was the earliest of several computer bus technologies used with PDP-11 and early VAX systems manufactured by the Digital Equipment Corporation of Maynard, Massachusetts.-History:...
cabling; a terminator was installed in the farthest drive.
The 16-bit (Unibus) controller was known as the RK11; it allowed the connection of up to eight RK05 drives. Seeks could be overlapped among the drives but only one drive at a time could transfer data.
The most-common 12-bit (Omnibus) controller was known as the RK8E; it supported up to four RK05 drives. The RK05 disk had more than 4096 sectors and so could not be addressed completely by a single PDP-8 12-bit word. To accommodate this, the OS/8
OS/8
OS/8 was the primary operating system used on the PDP-8 minicomputer developed by Digital Equipment Corporation of Maynard, Massachusetts. OS/8 was originally called MS/8 and, for a brief time, PS/8 before Digital settled on the name OS/8 in 1971.A virtually identical version of OS/8, called...
operating system split each drive into two logical volumes, for example, RKA0 and RKB0, representing the outermost and innermost cylinders of the drive.
Variants
- The RK05E was the final version of the standard-density RK05 drive. It contained many reliability enhancements compared to the earlier versions.
- An RK05F was later produced. By "fixing" the otherwise removable cartridge in place, it was able to avoid the cartridge-to-cartridge compatibility problems that limited the capacity of the ordinary RK05. As a result, it could operate at twice the normal track density, doubling the capacity of the drive to about 5MB.
- Prior to the introduction of DEC's own drives, DEC resold two drives from Diablo Data SystemsDiablo Data SystemsDiablo Data Systems was a division of Xerox created by the acquisition of Diablo Systems Inc. in 1972.It is best known for the Diablo 630 daisywheel printer, but also produced the hard disk drives that were resold by DEC as the RK02 and RK03....
(later acquired by XeroxXeroxXerox Corporation is an American multinational document management corporation that produced and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies...
). Known as the RK02 (very few shipped) and RK03 (Diablo Model 31), these were interface compatible with the RK05; RK03 and RK05 disks could be interchanged as well.