What does this look like from software? Is there just 128 MB of RAM at the start of memory that's unusually fast, or something else? Do kernels know about it? What do they do with it?
I wonder if in the future we'll have motherboards with two cpu-like sockets, except the other has an e-dram only chip. I assume the performance is better than regular dram.
The point of eDRAM is to gain performance moving it on the same module or die, so I'm not sure it buys you anything to put it in a different socket, you still have to go over the bus to get it. Usually eDRAM's structure doesn't make it perform better than any other DRAM, it just makes it able to be put on die or on package.
I am not sure why you are being down voted. This is exactly right. Stacked memory is the future in order to enable extremely parallel ultra low latency access to memory.
Putting it over a bus to elsewhere on the motherboard defeats the purpose, and even in graphics cards where manufacturers have complete control and can run a ton of traces to the memory, they are moving towards stacked memory. I believe pascal, nvidias next GPU, will feature it unless the roadmap recently changed.
Right. Individual DRAM cells are much slower than the SRAM cells used in the rest of a chip's cache system but they're also much denser which is why they're used for main memory. But IBM found that for large last level caches the shorter wires enabled by size savings of eDRAM were enough to offset the slower cells leading to a faster cache overall.
Interesting heat dissipation challenges with vertically stacked CPU's. I wonder if there would be advantages to stacking alternating layers of CPU core, DRAM, CPU, DRAM...
For cooling purposes, is it feasible to put a solid-state Peltier cooler integrated onto the die? The first thing that comes to mind is the energy costs but I would think that it would be less than sending current through a fan motor.
By disabled, do you mean the same processor design being binned into varying qualities of chip? In that case, it seems much more cost effective, and environmentally friendly, to send out chips with bad sections disabled at a lower price rather than to chuck them out.
I've been playing with the Renesas RZ/A1 line, which comes with three sizes of eDRAM on board: 3, 5, and 10MiB. The price differences between them are so large it sure seems like they're binning the parts.
