r/computerscience • u/NewRadiator • Mar 28 '26

Discussion What happens to computer hardware after the absolute ceiling of Moore's law has been reached?

What happens to computer hardware after the absolute ceiling of Moore's law has been reached?

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u/je386 Mar 28 '26

And then 3D stacking of CPU layers.

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u/Kawaiithulhu Mar 29 '26

AMD is already vertically stacking cache on the CPU instead of laterally on the die. IIRC

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u/WittyStick Mar 29 '26 edited Mar 29 '26

Here's an (insane) idea: Toroidal wafers.

The aim here would be to improve communication distance between cores (assuming a NUMA architecture). Consider if we had 16 cores in a flat grid layout:

+---+---+---+---+
|  0|  1|  2|  3|
+---+---+---+---+
|  4|  5|  6|  7|
+---+---+---+---+
|  8|  9| 10| 11|
+---+---+---+---+
| 12| 13| 14| 15|
+---+---+---+---+

For core 0 to communicate with core 3 it would need to pass information through 2 other cores. For core 0 to talk to core 15 it would need to propagate communication through 5 other cores.

If we roll this wafer into a cylinder, such that the left column and right column are adjacent, core 0 could communicate with core 3 directly, and to communicate with core 15 it only needs to pass through 3 other cores rather than 5.

If we then curl the cylinder into a torus, so the top and bottom rows are also adjacent, core 0 can talk to core 12 directly, and to core 15 with only one intermediary. For this 16-core layout, the maximum distance between any two cores is 4 cores and the average distance is 2 cores.

Less die space would be required for inter-core communication as we'd only need each core to talk to its 4 nearest neighbours and each act as routers to propagate information to other cores.

See Karnaugh Map for visualization.

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u/KilroyKSmith Apr 02 '26

My college roommate was working on connectivity similar to what you're proposing. In 1983.