Software Thread Integration (STI) and Asynchronous STI (ASTI) are compiler techniques which interleave functions from separate program threads at the assembly language level, creating implicitly multithreaded functions which provide low-cost concurrency on generic hardware. This extends the reach of software and reduces the need to rely upon dedicated hardware. STI and ASTI are driven by two types of timing requirements: thread-level (e.g. the delay between an event occuring and a service thread running) and instruction-level (e.g. when a specific instruction or code region must begin executing relative to the start of the function or another such instruction or region). These coarse- and fine-grain approach provide a precise method of defining timing requirements. STI provides synchronous thread progress; both functions proceed lock-step. ASTI provides asynchronous (independent) thread progress through the use of lightweight context switches (coroutine calls) between primary and secondary threads. The primary thread has hard-real-time constraints, while the secondary thread is not real-time, or has much longer deadlines.