Prefetching in a lower level exclusive cache hierarchy

An apparatus comprising:

• one or more processor cores, wherein each core comprises:
• a multi-tiered cache system, comprising at least one upper cache tier relatively closer, hierarchically, to a core's executing unit and at least one lower cache tier relatively closer, hierarchically, to a system memory, and
• a prefetcher circuit coupled with a lower cache tier of the respective multi-tiered cache system, and configured to issue a speculative prefetch request for data, wherein for each request for data the respective multi-tiered cache system is a requesting respective multi-tiered cache system and the respective prefetcher circuit is a requesting prefetcher circuit;
• and
• a memory interconnect circuit, hierarchically between the processor cores and the system memory, wherein the memory interconnect circuit is configured to cancel the speculative prefetch request if the data exists in an upper cache tier of the requesting multi-tiered cache system.

A system comprising:

• a computer processor, comprising one or more processor cores, wherein each core comprises:
• a multi-tiered cache system, comprising at least one upper cache tier relatively closer, hierarchically, to a core's executing unit and at least one lower cache tier relatively closer, hierarchically, to a system memory, and
• a prefetcher circuit coupled with a lower cache tier of the respective multi-tiered cache system, and configured to issue a speculative prefetch request for data, wherein for each request for data the respective multi-tiered cache system is a requesting respective multi-tiered cache system and the respective prefetcher circuit is a requesting prefetcher circuit;
• a memory interconnect circuit, hierarchically between the processor cores and the system memory, wherein the memory interconnect circuit is configured to cancel the speculative prefetch request if the data exists in an upper cache tier of the requesting multi-tiered cache system;
• and
• the system memory configured to store data.