| 摘要 |
A loop cache (26) is used in a data processing system for supplying instructions to a CPU to avoid accessing a main memory. Whether instructions stored in the loop cache can be supplied to the CPU is determined by a distributed TAG associated with the instruction address computed by the CPU. The instruction address includes an LCACHE index portion (42), an ITAG portion (44), and a GTAG (46). LCACHE index (42) selects corresponding locations in each of an ITAG array (50), an instruction array (52), and a valid bit array (54). A stored GTAG value (48) is chosen irrespective of where LCACHE index (42) is pointing. The GTAG portion of the instruction address (40) is compared to the stored GTAG value (48). The ITAG portion (44) of instruction address (40) is compared with the indexed ITAG of the ITAG array (50). If both the GTAG and ITAG compare favorably, the instruction is supplied from the loop cache to the CPU, rather than from main memory.
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