Honeywell 6000 Series Reference Manual page 17

Table 2 -1. Functional Characteristics of the Disk Storage Unit
Characteristic Description
Removable Disk Pack
Spindle Rotation
Disk Latency Time
Heads
R/W Heads
Loading Mechanism
Servo Heads
Recording
Mode
Data Rate
Density - outer track
Density - inner track
Head Positioning Times a
(Track -to - Track)
M4050 (or equivalent)
3600 rpm
8.3 ms (average)
16.7 ms (maximum)
19
Ramp
I
Modified Frequency Modulation (MFM)
806,000 bytes per second
2684 bpi
4040 bpi
55 ms (maximurn)
30 ms (average)
10 ms (minimurn)
a Does not include disk latency time or time to read data. Average head
selection time
=
6
IJ.
s
Disk Pack
The disk pack used with the DSU is a removable, interchangeable disk with 19 magnetic
recording surfaces numbered 0 - 18 (see Figure 2 -5). Each recording surface has 411
concentric tracks for a maximum total of 7809 tracks. The tracks on each recording surface
are numbered 000 - 410, track number 410 being the innermost. A group of 19 tracks
(tracks with the same number for each of the 19 recording surfaces) constitutes a cylinder.
i. e., tracks numbered 001 for each of the 19 recording surfaces comprise cylinder 001.
So, there are 411 cylinders for each disk pack. Cylinders 000 through 409 (7790 tracks) are
allocated to user data, system labels, catalogs, alternate tracks, and other information:
cylinder 410 (19 tracks) is reserved for T & D use only. Of the 410 cylinders available,
404 cylinders are addressable, three cylinders are reserved as aiternate cylinders. and
three additional cylinders are addressable to offset any tracks that are deallocated.
2 -5 DB37