Appeal No. 94-3596
Application No. 07/689,655
or more of the data processing units 10 via data couplers 12 and
communication link 11. Figure 2 of Vince is a diagram of one of
the data processing units 10. When the processor 14 in the data
processing unit updates a shared data item, a message containing
the updated value of the data item and its address is generated
and is transmitted via output buffer 18 and the link 11 to the
other data processing units 10 (column 1, lines 58 through 64).
When the message is received by the other data processing units,
it is used to update the copies of the shared data item held in
the stores of those data processing units to thereby ensure that
all copies of the shared data item are kept consistent (column 1,
lines 65 through 68). The operation of a data processing unit
that transmits an update message on the link is suspended if it
receives an update message from another data processing unit
while there are one or more update messages still outstanding
from the transmitting data processing unit (column 5, lines 57
through 60). The operation of the transmitting data processing
unit is suspended because the received message may overwrite a
data item which has already been updated by the transmitting data
processing unit at the time it created the outstanding data
message. Without the suspension in operation, a data item may be
overwritten by a chronologically earlier data value (column 5,
5
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Last modified: November 3, 2007