The Physical, Or Hardware, Structure Of The Disk - IBM 1130 User Manual

Computing system

Hide thumbs Also See for 1130:

Table of Contents

THE PHYSICAL, OR HARDWARE, STRUCTURE OF

Each IBM 2315 disk cartridge contains 512,000 words

organized into 200 cylinders of eight sectors each;

a sector, in turn, contains 320 words (see Figure

80.1). This is a very rigid organization dictated by

the basic design of the 1130.

A cartridge,

200 cylinders

512,000 words

1600 sectors

Figure 80.1. Disk storage definitions

An entire cylinder (eight sectors) is accessed by

one setting of the disk read/write heads.

to read or write from a cylinder other than the one

at which the heads are now set, the disk arm must

be moved to the new cylinder. The disk mechanism

moves the arm directly from the old position to the

new position in steps of one or two cylinders.

does not return to a "home" position first, as some

other disk units do.) Both single steps and double

steps take the same length of time: 15 milliseconds

(.015 seconds). To move nine cylinders, you need

four 2-cylinder moves (4x15 or 60 milliseconds)

plus one I-cylinder move (15 milliseconds) -- a

total of 75 milliseconds. A move of ten cylinders

takes the same amount of time -- five 2-cylinder

moves (5x15 or 75 milliseconds). Figure 80.2 shows

some representative arm movement times.

Stabilization

Many Cylinders

Figure 80.2.

Chapters

Table of Contents