Program Assigned Hardwired Supervisor Call Instructions
Original Publication Date: 1978-Jul-01
Included in the Prior Art Database: 2005-Feb-21
Hardware Supervisor Call (SVC) functions are provided which enhance the performance of a central processing unit (CPU) but retain the ability to execute custom or previously written operating systems. The hardware SVC functions are mapped into the firmware (microcode) of the CPU, such as the Model 4955 Processor Unit used in the IBM Series/1 system, and yet remain compatible with previous software systems which ran on prior systems. All desired operating system functions are written into the processor's microcode. The standard SVC operation instruction is coded along with the different supervisor functions. Each of these functions has a starting address in the microstore, as shown below.