IBM System/370 Guide

Page of GC20-1730-0
Added 11/20/70
By TNL GN20-2277
unit in which it is installed to address tape units that are attached
to an interconnected control unit. Figure 20.25.1 shows the switching
feature requirements for permissible switching combinations. The
switch combinations shown for switching control units among up to 16
tape units are the same that are required for switching control units
among up to 8 tape units.
A two control unit switching configuration is required to replace
the 2804 and 2404 read-while-write control units. The advantage of
the tape switching approach is that for a small price increment better
performance is possible. This is true because any two tape operations
can be active concurrently in a switched configuration (including two
reads or two writes) while the degree of simultaneity achieved using
a read-while-write control unit is application dependent. That is,
the application must lend itself to reading, then writing (or vice
versa) •
3803
Basic control
1 X 8 unit with no
switching
3803
. Communicator
2 X 16
Two-Control
3 X 16
4 X 16
Switch
3803
Communicator
Three-Control
Switch
3803
Communicator
Four-Gontrol
Switch
Figure 20.25.1.
3803
3803
Communicator
Two-Control
Switch
3803
Communicator
Three-Control
Switch
Communicator
Four-Control
Switch
3803
Communicator
3803 3803
Communicator
Communicator
Tape-switching configurations for the 3803/3420
Magnetic Tape Subsystem
51.6

IBM System/370 Specifications

General

Brand	IBM
Model	System/370
Category	Server
Language	English