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

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 the L4$. The L4$ caches bother GPU and CPU memory accesses; memory is partitioned between. 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 disclose much 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
Family	Number	Launch Date	Cores	Threads	Clock	Lithography	TDP	Die Size
Core i7	4950HQ	Q3 2013	4	8	2.4 GHz	22 nm	47 W	37.5mm x 32mm
Core i7	4850HQ	Q3 2013	4	8	2.3 GHz	22 nm	47 W	37.5mm x 32mm
Core i7	4750HQ	Q3 2013	4	8	2 GHz	22 nm	47 W	37.5mm x 32mm
Core i7	4960HQ	Q4 2013	4	8	2.6 GHz	22 nm	47 W	37.5mm x 32m
Core i7	4770R	Q2 2013	4	8	3.2 GHz	22 nm	65 W	37.5mm x 32mm
Core i5	4570R	Q2 2013	4	8	2.7 GHz	22 nm	65 W	37.5mm x 32mm
Core i5	4670R	Q2 2013	4	8	3 GHz	22 nm	65 W	37.5mm x 32mm

External links

• Intel Crystal Well Products