Parallel caches operating in exclusive address ranges
View Patent ↗A cache memory of the present invention includes a second cache memory that is operated in parallel with a first cache memory, a judgment unit which, when a cache miss occurs in both of the first cache memory and the second cache memory, makes a true or false judgment relating to an attribute of data for which memory access resulted in the cache miss, and a controlling unit which stores memory data in the second cache memory when a judgment of true is made, and stores the memory data in the first cache memory when a judgment of false is made.
1. A data processing system, comprising:
a processor
a first cache memory,
a second cache memory that is operated in parallel with said first cache memory and physically separated from said first cache memory by an address range,
a comparator operable, when a cache miss occurs in both said first cache memory and said second cache memory, to make one of a true judgment and a false judgment relating to an access address of memory data for which memory access resulted in the cache misses, and
a controller operable to store the memory data in said second cache memory when the true judgment is made, and store the memory data in said first cache memory when the false judgment is made,
wherein said processor accesses a data entry in said first cache memory when there is a cache hit in said first cache memory, and accesses a data entry in said second cache memory without any data transfer between said first cache memory and said second cache memory when there is a cache hit in said second cache memory, wherein
there is no case in which the memory data of the access address judged to be true and stored in said second cache memory is stored in said first cache memory for physically separating said second cache memory from said first cache memory by the address range.
2. The data processing system according to claim 1 ,
wherein said comparator is operable to judge whether the access address is within a specific address range.
3. The data processing system according to claim 2 , further comprising:
a holding register operable to hold the specific address range.
4. The data processing system according to claim 3 ,
wherein said holding register is written into by said processor executing an instruction for storing a value in said holding register.
5. The data processing system according to claim 1 ,
wherein a capacity of said second cache memory is smaller than a capacity of said first cache memory.
6. The data processing system according to claim 5 ,
wherein said first cache memory is a set associative cache memory, and
said second cache memory is a full associative cache memory.
7. The data processing system according to claim 5 ,
wherein said first cache memory has N1 ways, and each way of said first cache memory has N2 entries,
said second cache memory has M entries, and
M is smaller than N1 and N2.
8. The data processing system according to claim 7 ,
wherein M is 2.
9. The data processing system according to claim 3 ,
wherein said first cache memory is a set associative cache memory, and
said second cache memory is a full associative cache memory.
10. The data processing system according to claim 3 ,
wherein a capacity of said second cache memory is smaller than a capacity of said first cache memory.
11. The data processing system according to claim 10 ,
wherein said first cache memory is a set associative cache memory, and
said second cache memory is a full associative cache memory.
12. The data processing system according to claim 10 ,
wherein said first cache memory has N1 ways, and each way of said first cache memory has N2 entries,
said second cache memory has M entries, and
M is smaller than N1 and N2.
13. The data processing system according to claim 12 ,
wherein M is 2.
14. The data processing system according to claim 13 ,
wherein said holding register is accessed by said processor.