The next generation will have single precision hardware floats, but that's still at the prototype stage (with little bits of the processor running on a monster FPGA in the lab).
The key however is that SpiNNaker is a MIMD system (the cores are really independent of each other, except for a shared clock and chip-level shared co-packaged SDRAM) with a very fancy fast multicast interconnect that's been tuned for handling small source-routed packets without guaranteed delivery (but with guaranteed detection of failure to deliver). It's the almost complete antithesis of MPI, and it is by using that well that we get great performance in neural simulation. (I'm a software developer on the team.)
The key however is that SpiNNaker is a MIMD system (the cores are really independent of each other, except for a shared clock and chip-level shared co-packaged SDRAM) with a very fancy fast multicast interconnect that's been tuned for handling small source-routed packets without guaranteed delivery (but with guaranteed detection of failure to deliver). It's the almost complete antithesis of MPI, and it is by using that well that we get great performance in neural simulation. (I'm a software developer on the team.)