RCA 301, Programmer'S Reference Manual, Page: 24 / 235

contains 10 cells of 900 characters each. The total capacity of the file is over 4.6 million characters. Data may be
stored in each cell in any quantity up to 900 characters. Blocks of one to ten cells may be transferred between
HSM and the Data Record File with one instruction, at the rate of 2,500 characters per second.
The records of the Data Record File can be easily removed and exchanged. A single instruction, once initiated,
will search for and select a record, put the record on the turntable, and position the arm over the correct band,
without interrupting other Processor activity.
A total of six Data Record Files can be used in an RCA 301 System, two through individual Control Modules
and four through the Record File Mode Control. Three of the Files can be transferring data at the same time, one
in the Normal Mode, one in the Simultaneous Mode, and one in the Record File Mode. A Band Search can be taking
place in all six of the files at one time.
A parity check is performed on the information to be written on the record and on the address of the data to be
selected. An automatic write lockout feature is provided to prevent accidental writing on master records.
DATA DISC FILE
The Data Disc Files provide large capacity rapid random-access storage for data and computer programs.
Data is recorded on both sides of the magnetic discs. There are 9 zones of 128 tracks on each disc surface,
and each track contains 10 sectors of 160 characters. The total capacity of one module is 22,118,400 alphanumeric
characters. Blocks of from one to ten sectors may be transferred between High-Speed Memory and the File with one
instruction. When the strata concept of data organization is utilized, associated records of data stored within related
tracks of each zone on each disc surface are accessible within a single file positioning. There are 108 related tracks
per module for each strata.
"Access time" consists of the sum of two functions: (1) moving the read-write heads to the selected track, and
then (2) waiting for the disc to revolve to the point that the beginning of, data to be read is positioned under tht
heads. The latter function is termed "latency." Minimum access time to locate and start reading data is 5 milliseconds
Access time is as follows:
Minimum Average Maximum
363-2 70 130 200
363-3 70 150 210
363-4 • 75 170 235
363-5 75 170 235
Once initiated, a Track Select proceeds independently of other computer processing.
Information is recorded bit-serially in each track. Each zone has one read-write head serving 128 tracks. All
read-write heads in a file are moved simultaneously so that when an arm is positioned to a particular track in a
particular zone, all arms are positioned to the corresponding track within their respective zones.
Two Files can be transferring data to or from the High Speed Memory at the same time, one in the Normal
Mode and one in the Simultaneous Mode.
A parity check is performed on the information to be written on the disc and on the information read from the
disc. A check is made to determine that the positioner is on the correct track of the disc. Conversion from bit-serial
to character-serial operations are checked by a bit counter.
3488 UNIT
General Description
The Model 3488 Random Access Computer Equipment represents a mass storage device in excess of 5.4 billion
characters on line to a 301 processor.
Data is recorded on one side of 16 inch by 4]/
2
inch flexible magnetic cards.
These cards are housed in groups of 256, which are called magazines.
Up to 8 magazines are contained in a basic retrieval unit. Eight additional magazines can be added giving the
device a 16 magazines maximum (see figure 1).
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