Selector Channels; Block Multiplexing Operations With Rotational Position Sensing Devices - IBM System/370 145 Manual

drive can
be
used only as a spare. Listed below are the options
available for integrated and
channE~l
attached 2314 disk storage.
1.
2.
3.
4.
Facilitl!:
IFA with
3 to 8 drives
(87 to 233
million bytes)
IFA with
3, 6, 7, or 8
drives
(87 to 233
million bytes)
Channel with
2314A1 control
unit and
1
to
to 9 drives
(29 to 233
million bytes)
Channel with
2314B1 control
unit and 3, 6,
or 9 drives
(87, 174, or
233 million
bytes)
unit
2319A1
2312
2318
2313
2319A1
2319A2
2312
2318
2312
2318
2313
2319B1
2319B2
2319B2
Number of
Drives
3
1
2
4
3
3
1
2
1
2
4
3
3
3
Millions
of B~tes
87
29
58
116
87
87
~9
58
29
58
116
87
87
87
Notes
The 2319A1 must be
first unit attached
via the IFA. Any com-
bination of 2312, 2318,
2313, up to 5 drives,
can be added.
The 2319A1 must be
the first unit
attached via the IFA.
The 2319A2 must be
attached via the 2319A1.
Either one 2312 or one
2318 in addition to the
above can be added.
Any combination up
to nine drives (ninth
must be a spare).
The 2319B1 must be
the first unit attached
to the 2314B1. The
2319B2 must be attached
to the 2319B1.
The integrated file adapter is addressed as channel 1 and its drives
are addressed as 130 to 137. If the IFA is present, selectors 1 and 4
cannot
be
installed on the Model 145 and the standard selector is
addressed as channel 2. The IFA performs the functions of a selector
channel and disk control unit for the disk drives attached to it and is
programmed as though channel 1 and a control unit were present. The
Record Overflow and File Scan features are standard on the IFA.
However, 2844 Auxiliary Storage Control, the Channel Word Buffer, the
Channel-to-Channel Adapter, block multiplexing, and the Two-Channel
Swibch features do not apply to the IFA. In addition, the IFA cannot
handle data-chaining operations within the data area of a disk record.
SELECTOR CHANNELS
A single selector channel is standard on the Model 145. If the IFA
is not installed, selector channel 1 is standard and, optionally,
channels 2, 3, and 4 can be install,ed. If the IFA is present, selector
channel 2 is standard and only channel
3
can be added. The basic system
microcode includes all the microcodle required to support any
configuration of selector channels.
Selector channels on a Model 145 are functionally equivalent to
System/360 selector channels but support significantly higher data rates
than Model 30 and 40 channels. An individual selector channel without
the optional Channel word Buffer feature installed can sustain a data
rate of .82
MB,
while an aggregate 4channel data rate of 1.5MB for the
system is possible. Data is transf~~rred between a selector channel and
A Guide to the IBM System/370 Model 145 31