The GHC concurrency run time currently forces all delays to be resolved to 1/50th of second - independent of any of the run time settings (e.g. -V flag) - with rounding to the next 1/50th of second. This means that, in practice, the "jitter" in the time that a thread wakes as compared with can be rather large - 20ms to 30ms; 20ms from the GHC base library rounding along with a "jiffy" from the operating system. As far as I can see there is no reason why there should be any quantization of delay times - the implementation creates an ordered list of times which could be at any resolution (say microseconds) - this would reduce the "jitter" to that of an operating system jiffy. Thoughts? Neil