| 摘要 |
A priority scheme is utilized wherein various Instruction Processors possess predetermined levels of prioritization for gaining storage access. Basically, access locking devices used in this environment perform the function of allowing a single port requester to gain unlimited access to the storage unit port while preventing or locking out access by all other requesters seeking access to that same port. In operation, a plurality of pending prioritized port requests are "snapped" into a plurality of input latches. This snapping step is often referred to as a "snapshot". It is only during this "snapshot" period that pending port requests are allowed to enter the priority latches. In past systems, when a port request was made, accompanied by an access lock signal, all port requests presently residing in the priority latches waiting to be serviced were cleared out and no new requests were accepted into the latches until the next "snapshot" was performed. By causing these lower priority pending requests to be cleared out and not reinstated until a successive "snapshot", many such pending requests timed-out. This invention reduces the number of pending requests timing out.
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