The change of Delay from milliseconds to microseconds is ready for human review. (https://pharo.fogbugz.com/default.asp?14353) With this change from milliseconds to microseconds, clock rollover is eliminated, but it seems Delays run at reduced performance. newCodeEnabled FALSE TRUE 128507 101227 delays scheduled per second 100% 79% relative performance 7.8 9.9 microseconds per scheduled delay 100% 127% relative performance I "guess" this is due to the move from 32bit millisecond immediate SmallIntegers to 64bit microsecond boxed LargePositiveIntegers. It would be interesting to check this on Spur64, but for now, is this performance penalty a reasonable trade for eliminating delay clock rollover? The Delay class comment warns of the critical performance its high priority event loop, and on paper a 21% drop in performance seems significant, but actually the main Morph interCyclePause is 50 milliseconds. So... (9.9 - 7.8) / 50000 = 0.004% difference in performance. (Did I get that right?) Comments? P.S. DelayBenchmark results... =============== DelayBenchmark withNewCodeEnabled: true... #ConcurrentDelays: 1000 . Count: 39018 per second #ConcurrentDelays: 2000 . Count: 71906 per second #ConcurrentDelays: 3000 . Count: 98010 per second #ConcurrentDelays: 4000 . Count: 101227 per second #ConcurrentDelays: 5000 . Count: 64728 per second #ConcurrentDelays: 6000 . Count: 90495 per second #ConcurrentDelays: 7000 . Count: 89220 per second #ConcurrentDelays: 8000 . Count: 89585 per second #ConcurrentDelays: 9000 . Count: 88393 per second #ConcurrentDelays: 10000 . Count: 89073 per second DelayBenchmark withNewCodeEnabled: false... #ConcurrentDelays: 1000 . Count: 39498 per second #ConcurrentDelays: 2000 . Count: 77808 per second #ConcurrentDelays: 3000 . Count: 99889 per second #ConcurrentDelays: 4000 . Count: 117632 per second #ConcurrentDelays: 5000 . Count: 128507 per second #ConcurrentDelays: 6000 . Count: 118729 per second #ConcurrentDelays: 7000 . Count: 114437 per second #ConcurrentDelays: 8000 . Count: 114792 per second #ConcurrentDelays: 9000 . Count: 115137 per second #ConcurrentDelays: 10000 . Count: 113973 per second