View source for RA81 Disk Drive

[[Image:ra81.jpg|thumb|right|px200|4 RA81's in two cabinets]]

it's a dec disk drive.  for a wealth of [http://www.pdp-11.nl/peripherals/disk/ra81-info.html information]...



14" 456 MB fixed drive. 36 msec avg. seek time, 2.2 MB/sec, SDI 


The RA81 is a random-access, moving head (Winchester) fixed disk drive and was introduced in 1982.
It has a non-removable media using a head/disk assembly (HDA) with a capacity of 456 Mbytes.
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 controller and one or more disk drives.
Key figures are the following. 


*Storage capacity of 456 Mbyte in 16-bit word format
*Heat dissipation is 644 Watt nominal
*17.4 Megabit/sec peak transfer rate
*28 mSec. average positioning rate (average seek time)
*7 mSec. maximum positioning rate (cylinder to cylinder)
*50 mSec. maximum seek (innermost to outermost cylinder, in total 1258 cylinders)
*8.3 mSec. average rotational latency, rotational speed is 3600 RPM

== BSD disktab ==
<pre>
#
# 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:
</pre>


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