April 1, 1981
for frequently used VM/370 functions. The use of ECPS improves VM/370 performance beyond the performance gains that the virtual machine assist
feature provides. ECPS consists of three functions: • CP assist e Expanded virtual machine assist • Virtual interval timer assist
CP assist provides hardware assistance for frequeutly used paths of
specific CP functions.
Expanded virtual machine assist extends the hardware assistance that
the virtual machine assist feature provides for the instructions LPSW, STNSM, STOSM, and SSM. In addition, expanded virtual machine assist
provides hardware assistance for certain other privileged instructions.
virtual interval timer assist provides hardware updating of the
virtual interval timer at virtual address X'50'. Virtual interval timer
assist updates the virtual timer at the same frequency hardware updates
the real timer, 300 times per second. Thus, virtual interval timer
assist updates the virtual timer more frequently than CP updates it.
Because the timer is updated more frequently, accounting routines may be
able to provide accounting data that is more accurate. ECPS does not support the same functions and instructions on all
processors. Figure 13.1 lists the processors on which ECPS is
available, and identifies, by processor, the functions and instructions ECPS supports. 100 IBM VM/370 System programmer's Guide

Page of GC20-1807-7 As Updated April 1, 1981 by TNL GN25-0829
r'---- I I Functions and instructions CP_Assi§.i • Get free space (DMKFRE) • Release free space (DMKFRE) • Lock a page (DMKPTR) • Unlock a page (DMKPTR) • Test page status • Test page status and
lock (DMKCCW) • Store ECPS identification • SVC 8 (LINK) • SVC 12 (RETURN) • Scan for changed shared
paqes (DMKVMA) • Locate virtual I/O control
block (Dl'o!KSCN) • Invalidate paqe table (DMKVAT) • Invalid segment
table (DMKVAT) • Untranslate CSW (DMKUNT) • Free CCW storage (DMKUNT) • Locate real I/O control)
block (DMKSCN) • Common CCW command
processinq (DMKCCW) • Decode first CCW (DMKCCW) • Decode following CCW (DMKCCW) • Main entry to dispatch (DMKDSP) • Dispatch a block or a virtual
machine (DMKDSP) • LPSW • STNSM • STaSM • SSM • PTLB • SIa • SPT • SCKC • STPT • TCH • DIAGNOSE Processor 135-3,138, 1q5-3 148, 4341
x X X X X X x X X X X X X x X X x
x X X X X X X X X X X X X X X X X 3031 I 3031API 4331 X X X X X X x X X X X X X X X X X X x X X X X L- -I Figure 13.1. Functions and Instructions that ECPS Supports Part 2. Control Program 100.1