Arm and TSMC Showcase 7nm Chiplet, Eight A72 at 4GHz on CoWoS Interposer
anandtech.com
anandtech.com
Not the total power, but presumably still useful.
> The chip will never be sold in volume, but it proves that technologies by the two companies can enable designers to build complex chiplet-based products with unique characteristics.
So it's kind of interesting from a "is it possible to take the AMD approach to ARM cores" but it's not worth evaluating too hard because, again, you can't buy it.
I think ARM hopes this inspires one of the less creative licensees (Qualcom? Who else makes ARM besides Apple?) to pursue this as a product.
Ampere, Cavium, HiSilicon, Fujitsu are the ones with actually custom cores.
They already create and license cores, why not the substrate too? At the moment theres almost a binary choice for Arm using customers, either buy complete chips, or take Arm ip and roll your own, this seems like a useful third option.
Amazon (via Annapurna labs) with their Nitro chips. I'm pretty sure there are more, but that's the first one that came to mind.
If the chips are stacked on top of a communications backplane it would seem like that would be the case.
A single IC die (a "chiplet" when stacked on others) is made of a layer of transistors and wiring up to several hundred nanometers thick on top of a much thicker (several hundred micrometer) silicon wafer substrate.
Yep, stacking these dies ("chiplets") on top of one another is one form of 3D, and is definitely useful: IIRC, AMD's recent popular Ryzen 3000 line uses chiplets, and the Raspberry Pi's RAM chip is stacked on top the CPU (in a much cruder post-IC-manufacturing assembly process). The shorter distance between dies (compared to placing them in separate plastic packages on a PCB) can lead to maybe an order of magnitude improvement (in speed/power/etc). It's hard to stack more than a few layers.
The most ambitious form of 3D design (and the one most people probably think of) is multiple thin layers of transistors on a single die ("monolithic 3D"); this would give maybe another order of magnitude improvement. Monolithic 3D memory chips are becoming popular (V-NAND, etc), with the most recent at ~100 layers. Monolithic 3D CPUs are still an unsolved problem because they need different, more difficult process steps and better heatsinks (but we're close!).
Fyi, I don't think this is done in the most recent Pi 4
It's neat but really expensive, and I don't think the gains for RAM in that sort of designs are that big compared to computing cores outside of edge cases.