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Data Streaming Mode
The maximum data rate for block multiplexer channels 1 through 5 in each
standard channel group in a 4381 Model Group 14 or 3 Processor is 3 Mb/sec
each for data streaming mode of operation. The maximum aggregate data rate for
the ten standard block multiplexer channels is the sum of these rates, or 30
Mb/sec.
When the optional channel group is installed in a 4381 Model Group 14, each of
the six channels has a maximum data rate of 3 Mb/sec. The maximum aggregate
data rate for the nine channels in each group is 18 Mb/sec, providing a maximum
aggregate data rate of 36 Mb/sec for the two groups.
When the optional channel group is installed in a 4381 Model Group 3, channel 6
in each channel group has a maximum data rate of 3 Mb
I
sec, while channels 7 and
8 in each channel group can operate at a maximum of 2 Mb/sec each. The
maximum aggregate data rate of the nine channels in each group is 16 Mb/sec for
a maximum aggregate of 32 Mb/sec for the two groups.
Like a byte multiplexer, a block multiplexer channel can have multiple subchannels,
each of which can support one
1/0
operation. The setting of a channel mode bit
(0) in control register 0 determines whether the addressed subchannel of a block
multiplexer channel operates in block multiplexer mode (assuming it is capable of
operating in block multiplexer mode) or selector mode when a start instruction is
issued. The mode bit is set to 0 (selector mode) at IPL and can be altered by
programming at any time.
Data streaming mode of operation is standard for all the block multiplexer channels
present in a 4381 Model Group 14 or 3 Processor. Data streaming mode enables
all (Model Group 14) or certain (Model Group 3) 4381 block multiplexer channels
to handle faster data rates and all 4381 block multiplexer channels to handle a
longer channel-to-control-unit cable length. Specifically, a maximum
channel-to-control-unit cable length of approximately 122 meters (400 feet) is
supported for control units that are capable of operating in streaming mode and a
data rate of up to 3 Mb/sec can be achieved for this cable length for channels 1
through 8 in each channel group in a 4381 Model Group 14 and for channels 1
through 6 in each channel group in a 4381 Model Group 3.
Data streaming mode of operation is the same in all 4381 model groups, as
discussed in Section 20:20.
SIOF Instruction For System/370 Mode
The fast release function of the SIOF instruction and queuing of SIOF instructions
that are issued to a busy block multiplexer channel or control unit are designed to
reduce the time required to start I/
0 operations. These two facilities are the same
in all 4381 model groups, as discussed in Section 20:20.
80
A Guide to the IBM 4381 Processor
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