Crystal Well is the codename for the L4 cache, a discrete eDRAM silicon die, which is featured in the high-end Iris Pro-equipped Intel Haswell microprocessors. The eDRAM silicon die is separate from the main Haswell die but is packaged together with it. Crystal Well based processors started shipping in the third quarter of 2013.

Details

Crystal Well is a true 128MB L4$ which could be utilized by the core itself, not just by the Iris Pro's framebuffer. I.E. L3$ values that gets evicted go into L4$. The L4$ caches serve GPU and CPU memory accesses; memory is partitioned between the two. If the GPU is disabled, such as when a discrete GPU is installed, the L4$ will be used exclusively by the CPU.

Intel has not disclosed many technical specs regarding how the Crystal Well die communicates with the main die. Intel has stated that the cache is capable of delivering 100GB/s bandwidth (50GB/s in each direction).

Processors

Crystal Well Processors
Model	Family	Microarchitecture	Launched	Cores	Threads	Frequency	Process
i5-4570R	Core i5	Haswell
i5-4670R	Core i5	Haswell
i7-4750HQ	Core i7	Haswell
i7-4760HQ	Core i7	Haswell
i7-4770HQ	Core i7	Haswell
i7-4770R	Core i7	Haswell
i7-4850EQ	Core i7	Haswell
i7-4850HQ	Core i7	Haswell
i7-4860EQ	Core i7	Haswell
i7-4860HQ	Core i7	Haswell
i7-4870HQ	Core i7	Haswell
i7-4950HQ	Core i7	Haswell
i7-4960HQ	Core i7	Haswell
i7-4980HQ	Core i7	Haswell
E3-1284L v3	Xeon E3	Haswell

External links

• Intel Crystal Well Products