In the Spectre paper they note that while Chrome degrades the resolution of `performance.now()`, they were able to get a timer with sufficient resolution by usi

In the Spectre paper they note that while Chrome degrades the resolution of `performance.now()`, they were able to get a timer with sufficient resolution by using a Web Worker (thread) which repeatedly decrements a value in shared memory. As far as I know the EVM intentionally doesn't provide any concurrency because execution must be deterministic, and it seems doubtful that any kind of message-passing from outside the contract would be fast enough to provide the resolution needed. However, the block-lattice cryptos like RaiBlocks that find a way to build in concurrency and shared memory might be different.