IBM 1 Series - Sequence of Plugging Device Attachments; Processor I;O Channel Attachment Features; Channel Repower Feature

Sequence of Plugging Device Attachments
The recommended procedure for installing device attachments into the I/O
card file is to insert the attachment cards in an alphabetically descending
sequential order, with no empty sockets between cards. To facilitate the
removal of a device attachment from the I/O channel without interrupting
the poll propagation, a bypass mechanism has been provided. This makes it
possible to insert attachment cards in every other socket location without
breaking continuity, but it is not advised to do so. Should a user wish to
insert cards so that two or more empty sockets lie between two attachment
cards, provisions must be made to ensure continuity of poll propagation
when every other card of the ones installed are unplugged.
Processor I/O Channel Attachment Features
Channel Repower Feature
The channel repower feature, an IBM printed circuit card consisting of
IBM and TTL technology, is designed to repower the processor I/O
channel signal lines and to provide electrical isolation between I/O card
files.
The processor I/O channel is received at the bottom of the channel
repower feature card and the redriven signal lines are available at four
top-card connectors (Figure 2-32). In normal configurations, the channel
repower feature is plugged into the A-socket locations of the 4952, 4953
and 4955, or into the B-socket location of the 4959. The channel repower
feature can also be inserted into any I/O socket for cabling out to a
customer’s attachment or card file. When used for this purpose, the
repower feature must be the last series element directly plugged into the
I/O channel. (This last element could be in the 4952, 4953, 4955, or the
4959, depending on the system configuration.) This is because the feature
does not have any provision for propagating the poll back into the I/O
socket. The repower feature can drive 14 general unit loads, or equivalent,
through a maximum of 1.83 m (6 ft) of standard I/O channel cable. Only
one series cable can be used to attach these loads. The feature does not
provide dc logic voltages at its top-card connectors.
Channel repower card
Top card
connectors
(TCCs)
Processor backpanel
Cables
&m
WwW
wp
Figure 2-32. Channel repower feature—top card connectors
Processor I/O Channel 2-73