Difference between revisions of "RA81 Disk Drive"

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[[Image:ra81.jpg|thumb|right|px200|4 RA81's in two cabinets]]
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{{Infobox Disk drive
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| name = RA81
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| manufacturer = [[Digital Equipment Corporation|DEC]]
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| year introduced = June, 1982
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| controller = [[Standard Disk Interconnect#SDI Family of DSA Products|all SDI controllers]]
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| capacity = 456 Mbytes (formatted)
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| transfer rate = 17.4 Mbits/sec
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<!-- | average access time = xx msec -->
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| rpm = 3600
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| revolution time = 8.3 msec
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| one track seek = 7 msec
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| average seek = 28 msec
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| maximum seek = 50 msec
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| surfaces = 7 data, 1 servo
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| number of heads = 14 data,<br>1 servo (read-only)
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| tracks = 1258 (per head)
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| sectors = 52
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| bytes per sector = 512
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<!-- | tracks per inch = xx -->
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| density = 11,400
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| recording method = [[3/2 encoding]]
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| start time = 20 secs (max)
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| stop time = 20 secs (max)
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| physical size = 26cm x 44cm x 67cm
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| weight = 148 lbs
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| power consumption = 644 watts (idle)
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}}
  
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The '''RA81''' is a [[Digital Equipment Corporation|DEC]] [[disk|disk drive]], introduced in 1982. It is a moving [[head]] ([[Standard Disk Interconnect|SDI]] [[Winchester disk|Winchester]]) fixed disk drive. It has a non-removable media using a head/disk assembly (HDA) with a capacity of 456 Mbytes.
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[[Image:ra81.jpg|thumb|left|px200|4 RA81's in two cabinets]]
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The '''RA81''' is a [[non-removable-media disk]] drive from [[Digital Equipment Corporation|DEC]], introduced in June, 1982; it is member of the [[Digital Storage Architecture]]. It has a head/disk assembly (HDA) with a capacity of 456 Mbytes, and is a physically large drive (14-inch platters, in a heavy enclosure (10.5" x 16" x 36"); its nominal heat dissipation 644 watts.
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It had two heads per surface; not rotationally opposed (to halve maximum access time), but two on each arm; there thus 2,516 usable tracks on each data surface. It was internally operated by a pair of [[microprocessor]]s, which used 32-bit burst [[error-correcting code|ECC]] to invisibly repair simple data errors. An [[EIA RS-232 serial line interface|RS232]] port was provided for [[diagnostic]] purposes.
  
 
The RA81 connects to the [[device controller|controller]] via the [[Standard Disk Interconnect]] (SDI) bus. Additional drives can be connected to a controller to increase the data storage capacity. The RA81 can also be connected in a dual-[[hardware port|port]] arrangement permitting time-shared access by two controllers.
 
The RA81 connects to the [[device controller|controller]] via the [[Standard Disk Interconnect]] (SDI) bus. Additional drives can be connected to a controller to increase the data storage capacity. The RA81 can also be connected in a dual-[[hardware port|port]] arrangement permitting time-shared access by two controllers.
  
 
The RA81 is a self-contained disk drive with built-in cooling system and [[direct current|DC]] [[power supply]]. An RA81 disk drive subsystem is made up of an SDI disk controller and one or more disk drives.
 
The RA81 is a self-contained disk drive with built-in cooling system and [[direct current|DC]] [[power supply]]. An RA81 disk drive subsystem is made up of an SDI disk controller and one or more disk drives.
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==Specifications==
 
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Key figures are the following:
 
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* Storage capacity of 456 Mbyte in 16-bit word format
 
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* 1258 [[cylinder]]s
 
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* 17.4 Megabit/sec peak transfer rate
 
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* 28 mSec. average positioning rate (average seek time)
 
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* 7 mSec. maximum positioning rate (cylinder to cylinder)
 
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* 50 mSec. maximum seek (innermost to outermost cylinder)
 
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* 8.3 mSec. average rotational latency
 
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* 3600 RPM rotational speed
 
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* Heat dissipation 644 Watt nominal
 
  
 
==BSD disktab==
 
==BSD disktab==
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** [http://www.bitsavers.org/pdf/dec/disc/ra81/EK-0RA81-SV-001_Svc_Oct82.pdf RA81 Disk Drive Service Manual] (EK-0RA81-SV-001)
 
** [http://www.bitsavers.org/pdf/dec/disc/ra81/EK-0RA81-SV-001_Svc_Oct82.pdf RA81 Disk Drive Service Manual] (EK-0RA81-SV-001)
 
** [http://www.bitsavers.org/pdf/dec/disc/ra81/MP01359_RA81_Oct82.pdf RA81 Field Maintenance Print Set] (MP-01359)
 
** [http://www.bitsavers.org/pdf/dec/disc/ra81/MP01359_RA81_Oct82.pdf RA81 Field Maintenance Print Set] (MP-01359)
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* [http://bitsavers.org/pdf/dec/disc/brochure/RA60_RA80_And_RA81_Disk_Drives_Brochure_Aug82.pdf The RA60, RA80 and RA81 Disk Drives and The Digital Storage Architecture] - brochure
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* [http://bitsavers.org/pdf/dec/brochures/DEC-RA-FamilyOfWinchesterDiskDrives.pdf RA Family Of Winchester Disk Drives] - another brochure
 
* [https://www.pdp-11.nl/peripherals/disk/ra81-info.html RA81 information] - Henk Gooijen's extensive RA81 material
 
* [https://www.pdp-11.nl/peripherals/disk/ra81-info.html RA81 information] - Henk Gooijen's extensive RA81 material
 
** [https://www.pdp-11.nl/peripherals/disk/ra-images/ra81-open-model.jpg RA81 internals] - fantastic image of a sectioned RA81 drive
 
** [https://www.pdp-11.nl/peripherals/disk/ra-images/ra81-open-model.jpg RA81 internals] - fantastic image of a sectioned RA81 drive
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*  [https://archive.org/details/bitsavers_decdiscRA6vesBrochureAug82_2235969 The RA60, RA80 and RA81 Disk Drives] - combined [[RA60]]/[[RA80]]/RA81 sales brochure
 
  
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[[Category: DEC Disk Drives]]
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[[Category: SDI Disk Drives]]
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[[Category: DEC Non-removable-media Disks]]

Latest revision as of 02:16, 31 August 2023


RA81
Manufacturer: DEC
Year Introduced: June, 1982
Drive Controller(s): all SDI controllers
Capacity: 456 Mbytes (formatted)
Transfer Rate: 17.4 Mbits/sec
Revolutions per Minute: 3600
1/2 Revolution Time: 8.3 msec
One Track Seek Time: 7 msec
Average Seek Time: 28 msec
Maximum Seek Time: 50 msec
Total Surfaces: 7 data, 1 servo
Number of Heads: 14 data,
1 servo (read-only)
Tracks per Surface: 1258 (per head)
Sectors per Track: 52
Bytes per Sector: 512
Density: 11,400
Recording Method: 3/2 encoding
Start Time: 20 secs (max)
Stop Time: 20 secs (max)
Physical Size: 26cm x 44cm x 67cm
Weight: 148 lbs
Power Consumption: 644 watts (idle)


4 RA81's in two cabinets

The RA81 is a non-removable-media disk drive from DEC, introduced in June, 1982; it is member of the Digital Storage Architecture. It has a head/disk assembly (HDA) with a capacity of 456 Mbytes, and is a physically large drive (14-inch platters, in a heavy enclosure (10.5" x 16" x 36"); its nominal heat dissipation 644 watts.

It had two heads per surface; not rotationally opposed (to halve maximum access time), but two on each arm; there thus 2,516 usable tracks on each data surface. It was internally operated by a pair of microprocessors, which used 32-bit burst ECC to invisibly repair simple data errors. An RS232 port was provided for diagnostic purposes.

The RA81 connects to the controller via the Standard Disk Interconnect (SDI) bus. Additional drives can be connected to a controller to increase the data storage capacity. The RA81 can also be connected in a dual-port arrangement permitting time-shared access by two controllers.

The RA81 is a self-contained disk drive with built-in cooling system and DC power supply. An RA81 disk drive subsystem is made up of an SDI disk controller and one or more disk drives.

BSD disktab

#
# UCB RA81: use a-b-h-g or a-b-h-d-e-f
ucbra81|UCBRA81|DEC UCBRA81 Winchester:\
        :ty=winchester:ns#51:nt#14:nc#1248:\
        :dt=MSCP:\
        :pa#15884:oa#0:ba#8192:fa#1024:\
        :pb#33440:ob#15884:bb#4096:fb#512:tb=swap:\
        :pc#891072:oc#0:bc#8192:fc#1024:\
        :pd#15884:od#242606:bd#4096:fd#512:\
        :pe#307200:oe#258490:be#8192:fe#1024:\
        :pf#325382:of#565690:bf#4096:ff#512:\
        :pg#648466:og#242606:bg#4096:fg#1024:\
        :ph#193282:oh#49324:bh#4096:fh#512:

External links

Retrieved from "https://gunkies.org/w/index.php?title=RA81_Disk_Drive&oldid=31362"