IBM 4381 Manual page 18

The following channel features are provided for 4381 Processors.
Two channel groups are available for Model Groups 11, 12, and 13. The
standard channel group consists of one byte multiplexer and five block
multiplexer channels addressed 0 through 5. The optional channel group
consists of six block multiplexer channels addressed 6 through B. Block
multiplexer channel 5 in the standard channel group can be configured as a
byte multiplexer instead of as a block multiplexer channel.
For the 4381 Model Group 14, one channel group consisting of one byte
multiplexer channel (0) and five block multiplexer channels (1 through 5) is
standard for each of the two instruction processing functions. The fifth block
multiplexer channel in each channel group can be configured as a byte
multiplexer channel. Optionally, one additional channel group, which provides
three additional block multiplexer channels for each channel group (a total of
six additional channels) can be installed.
Functionally, a byte multiplexer channel for a 4381 Processor is equivalent to
that for System/370, 30XX, and other 4300 processors. The standard
(channel 0) and optional (channel 5) byte multiplexer channels in Model
Groups 11, 12, and 13 each have a 24Kb/sec maximum data rate (28Kb/sec
for the Model Group 14) for one-byte transfer operations for byte mode
operations. Unbuffered.burst mod.e 1/0 devices cannot be attached to the
byte multiplexer channels in a 4381 Processor.
Functionally, a block multiplexer channel in a 4381 Processor is equivalent to
that for System/370, 30XX, and 4300 processors. A block multiplexer
channel in 4381 Processors can also operate in selector channel mode.
The data streaming mode of channel operation that is provided for 4341 and
30XX Processors is standard for all the block multiplexer channels in a 4381
Processor. Data streaming mode enables certain 4381 channels to handle
faster data rates (up to 3Mb/sec) over a longer channel-to-control unit cable
length for attached control units that are also capable of operating in data
streaming mode (see discussion in Section 20:20). Both data streaming and
nonstreaming devices can be attached to the block multiplexer channels in a
4381 Processor.
For the standard channel group in a 4381 Model Group 11, 12, or 13, the
maximum aggregate data rate is 14 Mb/sec. For the optional channel group in
a Model Group 11, the maximum aggregate data rate is 8Mb/sec, providing a
22Mb/sec maximum aggregate for eleven block multiplexer channels. For a
Model Group 12, the optional channel group has a maximum aggregate data
rate of lOMb/sec, providing a 24Mb/sec maximum aggregate for the eleven
block multiplexer channels. The maximum aggregate data rate for the optional
channel group in a Model Group 13 is 16Mb/sec, with a 30Mb/sec maximum
aggregate data rate for eleven block multiplexer channels.
For the Model Group 14, a maximum aggregate data rate of 30Mb/sec for the
ten block multiplexer channels (15Mb/sec for each channel group) is possible.
The maximum aggregate data rate for 16 block multiplexer channels is
36Mb/sec (18Mb/sec for each eight-channel group).
Channels with data rates of up to 3 Mb/sec and the block multiplexing
capability support attachment to the 4381 Processor of 3380, 3375, 3370,
Section 01: Highlights
9