Enabling multiple instruction stream/multiple data stream extensions on microprocessors

Embodiments described herein disclose a system for enabling emulation of a MIMD ISA extension which supports user-level sequencer management and control, and a set of privileged code executed by both operating system managed sequencers and application managed sequencers, including different sets of persistent per-CPU and per-thread data. In one embodiment, a lightweight code layer executes beneath the operating system. This code layer is invoked in response to particular monitored events, such as the need for communication between an operating system managed sequencer and an application managed sequencer. Control is transferred to this code layer, for execution of special operations, after which control returns back to originally executing code. The code layer is normally dormant and can be invoked at any time when either a user application or the operating system is executing.