4. The load aap for your V!/370 system entry points, and their locations.
lists the modules and
5. Using the DKKCPI list to find the CP assist op code and entry
point name, and the load list to find the location of that
entry point, replace the CP assist instructions (X'E6xxxxxxxxxx') in those locations with three NOOPs (1'470000000700'). All CP assist instructions cause operation exceptions if ECPS is not The CP assist instructions are executed as NOOPs if the PSi is in supervisor state and VM/370 ECPS is installed but the CP assist is
disabled in control register 6. If VM/370 ECPS is installed but the PSi is in a problem state, the CP assist instructions cause privileged
operation exceptions regardless of the setting of control register 6 bit
6. EXPANDED VIRTUAL !ACHINE ASSIST Expanded virtual machine assist is part of the V!/370 Extended
Control-Program Support. Expanded virtual machine assist is hardware
that executes certain privileged operations issued by a V!/370 virtual
aachine. Expanded virtual machine assist is an extension of the Virtual !achine Assist feature. Expanded virtual aachine assist is invoked only
if virtual machine assist cannot execute the subject instruction in the
virtual machine, a corresponding virtual aachine assist function is
defined, and that virtual aachine assist function would present a
privileged operation exception. In soae cases, expanded virtual machine
assist does not completely execute the subject instruction.
The following table sum.arizes the operation codes, instruction naaes, amount of execution of the instruction by expanded virtual aachine
assist, and descriptions of the instructions:
Amount of
Trace Execution
Table of VK/370 Virtual Machine 2R 11l!!:I In§!!:Y£!!.Q!l rY!lf!!.Q!! 82 Yes LPSi Partial Load PSi B20D No PTLB Complete Purge Table Lookaside Buffer B206 Yes SCKC Partial Set Clock Comparator
9C Yes SIO,SIOF Partial Start I/O, Start I/O Fast B208 Yes 5PT Partial Set CPU Timer 80 Yes 5S! Partial Set System "ask AC Yes 5TNS! Partial Store Then AND System "ask AD Yes STOSM Partial Store Then OR System Mask B209 No STPT COllplete Store CPU Tiller 9F No TCH Complete Test Channel 1-420 IBM VM/370 System Logic and Problem Deterlination--Volume 1

Although all of the functions provided by expanded virtual machine
assist can be disabled by values in control register 6, any of the
functions of expanded virtual machine assist can be enabled or disabled by the setting of bits in a field defined in the MICBLOK (displace.ent 1'14', label MICEYMA) in conjunction with values in control register 6
that enable expanded virtual machine assist. Specifically, if bits 0 and 6 of control register 6 are both on and the real machine is in
virtual supervisor state, then the finer controls provided in the
specified MICBLOK field are active. If those two bits in control
register 6 are not both on, or if the real machine is not in virtual
supervisor state, then the settings of the MICBLOK assist controls are ignored. During virtual supervisor state execution, a particular function of
expanded virtual machine assist is enabled only if: • Expanded virtual machine assist is enabled in control register 6
(bits 0 and 6 are both on), and • The bit defined for that function in the MICBLOK assist control field
is on. Virtual machine assist is unaffected by the MICBLOK assist control
field.
Some bits in the MICBLOK ass1st control field enable and disable
several functions of expanded virtual machine assist. This is because
of the similarity in the definitions of the controlled functions. The
following table contains the bit definitions of the MICBLOK assist
control field. o Load PSi 1 Purge TLB
2 Set clock comparator, set CPU timer
3 Start I/O 4 Set system store then AND system mask,
store then OR system mask
5 Store CPU timer
6 Test channel
These MICBLOK assist control bits can also be used to enable or
disable all of expanded virtual machine assist. If bits 0 and 6 of
control register 6 are both on, and the assist control bits are off,
then CP assist is enabled but expanded virtual machine assist is
disabled. VIRTUAL INTERVAL TIMER ASSIST Virtual interval timer assist is the hardware support for an interval
timer in the virtual machine. The virtual machine may be in either EC
mode or BC mode. The virtual interval timer is in the virtual machine's
page frame 0 and functions like the real interval timer.
The virtual interval timer runs without either the CP assist or the
extended virtual machine assist being active. The virtual interval tiaer assist is only active if virtual machine assist is active. Bits 0 and 7 of control register 6 control the virtual interval timer assist.
Appendix A: VM/370 Extended Control-Program Support 1-421