297 page pdf that discusses a lot of the issues around making exaflop supercomputers
The latest petaflop supercomputers use 3-7 megawatts of power.
Managing power issues is one of the key challenges for future exaflop supercomputers.
The energy challenges to exascale computers were discussed at the recent SC08 conference
There are four challenges where current trends are lacking:
1. Energy and Power
2. Memory and Storage
3. Concurrency and Locality
4. Resiliency (handling faults, keeping error rates down)
Hybrid and superconducting circuits and many other options are examined.
Various architecture changes to current systems were examined at the Extreme computing conferences that looked at making Zettaflop supercomputers.
Onchip photonic processing was considered a key technology to accelerate existing systems.
Tensilica's reconfigurable processors and circuits are considered a candidate solution to making fast and energy efficient exascale computers.
A seti@home style network of teraflop class GPGPU systems could achieve exascale levels as early as 2010. One million teraflop class GPGPUs combined.