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TABLE 4-l. CARTRIDGE DISK UNIT CAPABILITIES
Cartridge Disk Unit
Data Storage Capacity
CDU9101
2.5/2.8 million bytes
CDU9102
5.0/5.6 million bytes
CDU9103
5.0/5.6 million bytes
CDU9104
10.0/11.2 million bytes
Functional Description and Characteristics
The recording media of the cartridge disk unit
is a single aluminum disk, housed in a perma
nently sealed, dust-free container. Each disk
contains two magnetic oxide coated recording
surfaces (both sides), and depending on the
application and configuration of the cartridge (see
Table 4-1), each surface contains 204 or 408
cylinders with either 12 or 24 equal length sectors
of 256 or 576 bytes respectively and with two or
four tracks per cylinder with a total formatted
capacity that may vary from 2,506,752 to
11,280,384 bytes.
All tracks consist of fixed length sectors that
are clocked by fixed slots inscribed into the
circumference of a disk. The number of sectors
per track, be it 12 or 24 (24 maximum), is a
function of software, thereby allowing variable
block sizes.
Disk cartridges can be fully interchanged only
between properly aligned drives having the same
track density.
When a drive is disk loaded and operative, the
magnetic heads on the drive will physically locate
and float directly above the recording surfaces of
the disk. During operation, there is never any
physical contact between the heads on the drive
and the recording surfaces of the disk.
The magnetic heads on the drive come into
physical contact with the recording surfaces of
the disk only when loading the drive with a disk.
With the drive disk loaded and ready to operate,
the drive spindle will automatically engage the
disk and rotate it at a speed of 2400 rpm. The
drive heads will break physical contact and float
over the recording surfaces of the disk.
CARTRIDGE DISK UNIT DESIGN
The cartridge disk unit has been engineered in
design to function as a highly reliable and
dependable random access storage device in the
areas of operation and maintenance. Cabinet
mounted, slide-in-slide-out units provide easy
access for loading/unloading disks; the adapta-
CARTRIDGE DISK
UNITS
Type of Disk
Density Unit
Recorded Data
Removeable
Low
100 tracks per inch
Removeablc
Low
100 tracks per inch
and fixed
Removeable
High
200 tracks per inch
Fixed and
High
200 tracks per inch
removeable
bility of a drive spindle to accept both remove
able and fixed disks and a file protect switch; are
design features of the drive making it a most
convenient and dependable device to operate and
maintain.
CARTRIDGE DISK UNIT CONFIGURATION
The four types of cartridge disk units available
and configured for Level 6 system use are the
CDU9101, 9102, 9103, and 9104, as shown in
Table 4-1. Disk drives are available singly with up
to a maximum of four drives capable of being
connected to one CDM91 0 1 Cartridge Disk Unit
Adapter. Specifications and prime disk drive
characteristics are described in Table 4-2.
INTERCONNECTIONS/SYSTEM
INTERF ACE
The cartridge disk unit interfaces with the
system bus of the Level 6 processor by means of
the MSC (Mass Storage Controller) and cartridge
disk unit adapter. The MSC91 0 1 controller is a
firmware-driven
microprogrammed
disk
con
troller. Multiple MSC can be attached to the Level
6 bus. However, no more than one disk adapter
can be attached to anyone MSC.
The MSC contains the circuitry necessary to
support the device adapter connections. All cir
cuitry pertinent to the cartridge disk unit is
contained in the cartridge disk unit adapter.
Through its adapter, each disk drive presents a
DMA (Direct Memory Access) interface to the
Level 6 processor. See Figure 4-2.
DATA TRANSFER AND DISK DRIVE SIMUL
TANEITY
Cartridge disk units attached to an MDC are
software addressable via channel numbers. Each
individual drive has two channel numbers as
signed, differing from each other only in the low
order bit position called the direction bit. When a
data transfer I/O command is issued to a bidirec
tional device such as the cartridge disk drive, the
direction bit of the channel number will specify
4-2
AT04
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