Compal-LA-1044 Schematic Circuit Diagram
Compal-LA-1044 Schematic Circuit Diagram
Processor Features
New features are regularly added to processor designs when new processors are produced, improving anything from performance in certain types of applications to the overall dependability of the CPU. The following sections take a closer look at a couple of these technologies (oldest first).
System Management Mode
Intel and AMD began introducing System Management Mode (SMM) to their CPUs in the early 1990s, prompted by the need for more robust power management capabilities in mobile computers. SMM is a special-purpose operating mode that takes care of low-level system power management and hardware control. System BIOS or low-level driver code can use SMM to create an isolated software environment that is transparent to the OS or applications software.
In October 1990, SMM was released as part of the Intel 386SL mobile CPU. In November 1992, SMM was included in the 486SL CPU, and in June 1993, it was included in the full 486 families. When the initial Pentium processors were launched in March 1993, SMM was noticeably lacking; however, SMM was implemented in every 75MHz and faster Pentium CPUs manufactured on or after October 1994. Around the same time, AMD added SMM to their improved Am486 and K5 CPUs. SMM has been included in all subsequent Intel and AMD x86-based CPUs released since then.
SMM is activated by signaling a particular interrupt pin on the CPU, which creates the highest-priority non-maskable interrupt available, the System Management Interrupt (SMI). When SMM starts, it saves the processor's context, or state, as well as any presently executing processes. The CPU then moves to a designated address area and executes the SMM code, which runs invisibly to the interrupted program and any other software on the system. When the SMM work is finished, a resume instruction restores the processor's and programs' previously preserved context or state, and the processor continues functioning exactly where it left off.
