IBM Series 1 User Manual page 97

Seguence of Plugging Qevic~ Attachments
The recommended procedure for installing device attachments
into the I/O card file is to insert the attachment cards in
an alphabetically
de~nd!.!!,g
sequential orde.r 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 in fact 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 in such
a way
that tvo or more empty sockets lie
between tvo attachment cards, provisions should be made to
ensure continuity of poll propagation when every other card
Q!
!h~ Q~~2 i~2talled
are unplugged.
PROCESSOR I/O
CHANNEL ATTACHMENT FEATURES
The channel repower feature is an IBM printed circuit card
consisting of IBM and TTL technology. It is designed to
repower the processor I/O channel signal lines and to
provide isolation between I/O card files.
The processor I/O channel is received at the bottom of
the channel repower feature card and the re-driven 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 4953
and 4955, or into the B-socket location of the 4959.
However, 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 4953, 4955, or the 4959 depending on the system
configuration.) This is because the feature does not have
any provision for
propagat~ng
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 ~ ft) of
standard I/O channel cable. More than one series cable
cannot be used in attaching these loads. The feature does
not provide dc logic voltages at its top card connectors.
2-82
GA34-0033
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