RA82 disk drive

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Manufacturer: DEC
Drive Controller(s): all SDI controllers
Capacity: 622 Mbytes (formatted)
855 Mbytes (un-formatted)
Transfer Rate: 2.4 Mbytes/sec
Average Access Time: 32.3 msec
Revolutions per Minute: 3600
1/2 Revolution Time: 8.3 msec
One Track Seek Time: 6 msec
Average Seek Time: 24 msec
Maximum Seek Time: 38 msec
Total Surfaces: 7 data, 1 data/servo (shared)
Number of Heads: 15 data,
1 servo (read-only)
Tracks per Surface: 1423 (usable, per head)
1435 (total, per head)
Sectors per Track: 57 (usable)
58 (total)
Bytes per Sector: 512
Tracks per Inch: 1063
Density: 12,545
Recording Method: MFM
Start Time: 50 secs (max)
Stop Time: 20 secs (max)
Physical Size: 26cm x 44cm x 67cm
Weight: 172 lbs
Power Consumption: 560 watts (idle)


The RA82 disk drive is a Standard Disk Interconnect non-removable-media disk drive from DEC. It is member of the Digital Storage Architecture. A physically large drive (14-inch platters, in a heavy enclosure 10.5" x 16" x 36"), its capacity was 622 Mbytes.

It had two heads per surface; not rotationally opposed (to halve maximum access time), but two on each arm; there thus 2,846 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 RA82 can also be connected in a dual-port arrangement, permitting its use by two controllers.

External links