L4cache
L4cache refers to a potential fourth level in a processor’s memory hierarchy. It is not a standard feature on mainstream CPUs, but it has appeared in some architectural designs and research prototypes as an additional, larger cache layer situated beyond the conventional L3 cache. The L4 cache may be implemented on the same processor package, on a separate die, or even as an off-die component connected to the memory subsystem, depending on the design.
In terms of placement and behavior, an L4 cache is typically larger and slower than L3 and
Common considerations for L4 caches include cache coherence, consistency with lower cache levels, and the trade-off
History and current status: the L4 cache concept has appeared primarily in academic literature and specialized