Nice resource, thanks.

If someone wonders why things look the way they do, so it's all about 
on-die and off-die memory. Either you use off-die or on-die memory, often 
SRAM which requires 6 gates per bit. So spending half a billion gates 
gives you ~10MB buffer on-die. If you're doing off-die memory (DRAM or 
similar) then you'll get the gigabytes of memory seen in some equipment. 
There basically is nothing in between. As soon as you go off-die you might 
as well put at least 2-6 GB in there.

The HMC memory allows improvements in execution time and consumed energy. In some situations, this memory type permits removing the L2 cache from the memory hierarchy.