3 ms·Not sure if relevant but dram refreshes continuously.by zasdffaa 4y agoNot sure if relevant but dram refreshes continuously.wahern 4y agoOn-die CPU caches typically use SRAM. Modern DRAM chips are already die-stacked in several layers. But maybe DRAM is more heat sensitive than SRAM, so more difficult to stack atop a stronger heat source?rbanffy 4y agoIIRC, the RPi SoCs have a DRAM chip stacked on top of the processor.