Abstract: A processing system removes the burden of maintaining legacy hardware by employing a system management mode mechanism to provide an environment for virtualizing preexisting memory and I/O space instructions into operations for high resolution raster graphics circuitry, thus maintaining functionality and backwards compatibility with preexisting software.

Abstract: An enhanced system management mode (SMM) includes nesting of SMI (system management interrupt) routines for handling SMI events. Enhanced SMM is implemented in an computer system to support a Virtual System Architecture (VSA) in which peripheral hardware, such as for graphics and/or audio functions, is virtualized (simulated by SMI routines). Reentrant VSA/SMM software (handler) includes VSA/SMI routines invoked either by (a) SMI interrupts, such as from non-virtualized peripheral hardware such as audio FIFO buffers, or (b) SMI traps, such as from accesses to memory mapped or I/O space allocated to a virtualized peripheral function. SMI nesting permits a currently active VSA/SMI routine to be preempted by another (higher priority) SMI event. The SMM memory region includes an SMI header segment and a VSA/SMM software segment--the SMI header segment is organized as a quasi-stack into which nested SMI headers are saved.