Editing IBM System/36 (section)

===Processors===
S/36s have two 16-bit processors, the CSP or Control Storage Processor, and the MSP or Main Storage Processor. The MSP is the workhorse; it performs the instructions in the computer programs. The CSP is the governor; it performs system functions in the background. Special utility programs are able to make direct calls to the CSP to perform certain functions; these are usually system programs like $CNFIG which is used to configure the computer system. As with the earlier System/32 and System/34 hardware, the execution of so-called "scientific instructions" (i.e. [[floating-point arithmetic|floating-point operations]]) is implemented in software on the CSP.<ref>{{cite web|url=http://www.bitsavers.org/pdf/ibm/system36/SC21-7908-3_System_36_Programming_with_Assembler_Jan86.pdf|title=System/36 Programming with Assembler|date=January 1986|access-date=2021-12-22|publisher=IBM|website=Bitsavers}}</ref>

The primary purpose of the CSP is to keep the MSP busy; as such, it runs at slightly more than four times the speed of the MSP. The first System/36 models (the 5360-A) have a 4&nbsp;MHz CSP and a 1&nbsp;MHz MSP. The CSP loads code and data into main storage ''behind'' the MSP's program counter. As the MSP is working on one process, the CSP is filling storage for the ''next'' process.

The 5360 processors came in four models, labeled 5360-A through 5360-D. The later "D" model is about 60 percent faster than the "A" model.