Another Limit: Speed of Light!
1 Tflop/s, 1 Tbyte sequential machine
r = 0.3 mm
Consider a hypothetical 1 Tflop/s sequential machine:
Data must travel some distance, r, to get from memory to CPU.
To get 1 data element per cycle, this means 1012 times per second at the speed of light, c = 3x108 m/s. Thus r < c/1012 =
Now put 1 Tbyte of storage in a 0.3 mm x 0.3 mm area:
Each bit occupies about 1 square Angstrom, or the size of a small atom.
No choice but parallelism