A system comprising: R racks, each rack comprising N nodes; each node comprising D dies; each die comprising C cores and a die shadow tag array; each core comprising P pipelines and a core shadow tag array; each pipeline associated with a data cache and a data cache tag array; each data cache being either non-coherent or coherent; and each coherent cache being associated with one of X coherency domains, and having cache lines with a modified, owned, exclusive, shared, invalid, or forward (MOESI-F) state; wherein each pipeline is configured to, when needing to read a cache line, issue a read request to its associated data cache, then, if need be, issue a read request to its associated core-level cache, then, if need be, issue a read request to its associated die-level cache, then, if need be, issue a no-cache remote read request to one of the D dies being mapped to hold the cache line, wherein when a no-cache remote read request is sent, the data that is read will be the most recent copy of coherent data within the one of the D dies; wherein the die shadow tag array is to track a current state of the cache lines at a per-core shadow tag granularity; wherein the core shadow tag array is to track the cache lines in the data caches associated with the pipeline; wherein participation in coherency by each of the C cores and each of the P pipelines is specified by a software-programmable model-specific register (MSR) comprised by the system; and wherein, for each of the P pipelines participating in coherency, a domain ID of a corresponding coherent domain is also specified in the MSR; wherein one of the P pipelines is configured to, when needing to transition a cache line state from a read to a write, send a transition request to the core shadow tag , and wherein the core shadow tag is configured to, when servicing the transition request, attempt to conserve power by only reading core shadow tag array entries that match the domain ID. R racks, each rack comprising N nodes; each node comprising D dies; each die comprising C cores and a die shadow tag array; each core comprising P pipelines and a core shadow tag array; each pipeline associated with a data cache and a data cache tag array; each data cache being either non-coherent or coherent; and each coherent cache being associated with one of X coherency domains, and having cache lines with a modified, owned, exclusive, shared, invalid, or forward (MOESI-F) state; wherein each pipeline is configured to, when needing to read a cache line, issue a read request to its associated data cache, then, if need be, issue a read request to its associated core-level cache, then, if need be, issue a read request to its associated die-level cache, then, if need be, issue a no-cache remote read request to one of the D dies being mapped to hold the cache line, wherein when a no-cache remote read request is sent, the data that is read will be the most recent copy of coherent data within the one of the D dies; wherein the die shadow tag array is to track a current state of the cache lines at a per-core shadow tag granularity; wherein the core shadow tag array is to track the cache lines in the data caches associated with the pipeline; wherein participation in coherency by each of the C cores and each of the P pipelines is specified by a software-programmable model-specific register (MSR) comprised by the system; and wherein, for each of the P pipelines participating in coherency, a domain ID of a corresponding coherent domain is also specified in the MSR; wherein one of the P pipelines is configured to, when needing to transition a cache line state from a read to a write, send a transition request to the core shadow tag , and wherein the core shadow tag is configured to, when servicing the transition request, attempt to conserve power by only reading core shadow tag array entries that match the domain ID. <EOS>