RA70 disk drive

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Manufacturer: DEC
Drive Controller(s): all SDI controllers
Capacity: 280 Mbytes (formatted)
350 Mbytes (unformatted)
Transfer Rate: 1.4 Mbytes/sec
Average Access Time: 27 msec
Revolutions per Minute: 4000
1/2 Revolution Time: 7.5 msec
Average Seek Time: 19.5 msec
Total Surfaces: 11 data, 1 servo
Number of Heads: 11 data,
1 servo
Tracks per Surface: 1507
Sectors per Track: 34
Bytes per Sector: 512
Tracks per Inch: 1355
Density: 22,437
Start Time: 59 secs (avg)
Stop Time: 15 secs (avg)
Physical Size: 9cm x 14.6cm x 22.4cm
Weight: 10.5 lbs
Power Consumption: 264 watts (idle)


The RA70 disk drive is a Standard Disk Interconnect non-removable-media disk drive from DEC. Unlike all the other RA-series drives, it is a compact width - 5.25 inches wide. It has no internal power supply; it gets its power from the host system, or its SA7x enclosure.

Its capacity was 280 Mbytes (formatted). It was internally operated by a microprocessor which used 32-bit burst ECC to invisibly repair simple data errors.

Further reading

  • RA70 Disk Drive Technical Description Manual (EK–ORA70–TD) - not available online
  • RA7x Disk Drive Service Manual (EK–ORA7X-SM) - not available online

External links