Appeal No. 2006-2217
Reexamination Control Nos. 90/006,789 and 90/007,420
equivalent to the "means counting each of the refresh request
signals." This is one difference.
Churchward has structure to determine when the count in
counter 96 reaches zero from eight, where zero represents a
"predetermined threshold value" of eight counts. Thus, in
isolation, Churchward seems to have "means, coupled to the
refresh request signal counting means, for comparing a value of
the counted refresh request signals to a predetermined threshold
value and for determining when a number of counted refresh
request signals equals or exceeds the predetermined threshold
value." However, since the value of the counted signals is not
the count of each of the refresh request signals, but only the
count of the refresh request signals when the memory is busy,
this limitation is not met when the claim is considered as a
whole. This is another difference.
The last limitation of claim 2 recites:
means, responsive to the comparing means determining
that a number of counted refresh request signals at least
equals the predetermined threshold value, for refreshing a
plurality of memory rows, the number of memory rows being
refreshed being substantially equal to the counted value.
Churchward does not refresh a plurality of memory rows "equal to
the counted value" "responsive to the comparing means determining
that a number of counted refresh request signals at least equals
the predetermined threshold value." Churchward burst refreshes a
number of rows equal to the count responsive to the memory
becoming not busy. When the counter reaches zero (representing a
count of eight), the only value that could be considered a
"predetermined" threshold value, Churchward starts refreshing
rows one at a time at a 15.6 microsecond rate if the memory is
still busy: it does not refresh eight rows. The number of memory
rows refreshed depends on the memory busy time, not the count.
"If the memory becomes not busy before a zero count is reached,
it counts back towards eight at a 450 nanosecond rate." (Col. 3,
lines 46-48.) Thus, if the memory was only busy for 3 counts,
the system would perform a burst refresh of 3 rows (each refresh
taking 450 nanoseconds) when the memory became not busy; i.e.,
the system performs a burst refresh of "up to" eight refresh
cycles (e.g., col. 8, lines 44-51). The burst refresh is not
dependent on the count being a predetermined value. This is a
further difference.
For these reasons, we find that Churchward does not teach
the added limitations of claims 2-5, 7-11, 13-16, and 18-20.
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