Thanks MJP, that sounds doable and sounds like it'd give me what I want.
@Jason - The simulation scales with O(n^3) at the moment, though I'm hoping to get that down to O(n^2), for some definition of N I can break up the tasks well enough to avoid the Windows' watchdog restarting the driver, but trying to timeslice it with rendering tasks would be a huge pain. If N is small, I can run dozens of complete simulation cycles per render frame (think of something like Simcity in fast forward). And if N is large, it can take dozens of render frames for each simulation frame. Decoupling the two seems fairly obvious, though you're right, I've never heard of anyone trying to do this.