RM80 Disk Drive

From Computer History Wiki
Jump to: navigation, search

Manufacturer: DEC
Year Introduced: October, 1980
Drive Controller(s): RH11, RH70, RH10, RH20, RH780, RH750
Capacity: 124 Mbytes
Transfer Rate: 1.2 Mbytes/sec
Average Access Time: 33.3 msec
Revolutions per Minute: 3600
1/2 Revolution Time: 8.3 msec
One Track Seek Time: 6 msec
Average Seek Time: 25 msec
Maximum Seek Time: 50 msec
Total Surfaces: 7 data, 1 servo
Number of Heads: 14 data,
1 servo (read-only)
Tracks per Surface: 561 (18-bit word mode)
559 (16-bit word mode)
Sectors per Track: 30 (18-bit word mode)
31 (useable; 16-bit word mode)
Words per Sector: 256 (16-bit word mode)
Tracks per Inch: 478
Density: 6339 (max; inner track)
Recording Method: MFM
Start Time: 20 secs (avg);
40 secs (max)
Stop Time: 9 secs (avg);
13 secs (max)
Physical Size: 26cm x 44cm x 67cm
Weight: 135 lbs (approx)
Power Consumption: 575 watts


The RM80 Disk Drive was a MASSBUS non-removable-media disk from DEC; it held 124 MB. It was apparently the MASSBUS version of the R80 Disk Drive; it could support either 16- or 18-bit words. It was internally operated by a microprocessor which used 32-bit burst ECC to invisibly repair simple data errors.

It had two heads per surface; not rotationally opposed (to halve maximum access time), but two on each arm; there were thus 1,122 usable tracks on each data surface (in 18-bit word mode; 4 tracks were reserved for maintenance purposes in 16-bit mode). 1 sector per track was reserved for bad block replacement in 16-bit word mode, out of 32 total.

The RM80 can also be connected in a dual-port arrangement, permitting its use by two controllers.

Further reading

  • RM80 Disk Drive Technical Description Manual (EP-0RM80-TD-001) - not available online, but in microfiche
  • RM80 Disk Drive Service Manual (EP-0RM80-SV-001) - not available online, but in microfiche

External links