If the three above design and coding restrictions are adhered to, the CP module can be added to the existing pageable nucleus modules by
utilizing the service routine, V!FLOAD, which is described in "V!/370 Maintenance Procedures" of the !!l37Q ~~i£~ ~Q~tine§ PrQg~~ Loqi£. Additional information can be found in the V!LJ1Q fl~~ninq !ag SIst~! ~~~!§!!~ ~Yig!· E!~ut!Bl! !!§ig!nt !1ggul!§ DMKBSC DMKGRF DMKPRG DMKSSS DMKCCH DMKGRT D!KPRV D!KSTK DMKCCW DMKHVC DMKPSA DMKSVC DMKCFI1 DMKIOE DMKPTR D!KT!R DMKCNS DMKIOS DMKQCN D!KTRK DMKCVT DMKLOC D!KRGA D!KUNT D!KDAS D!KLOK DMKRGB D!KVAT DMKDGD D!KMCH DMKRNH DMKVCN DMKDMP D!KMCT DMKRPA DMKVIO DMKDSB DMKllSW DMKRS:P DiiKV5A DMKDSP DMKOPR D!KSCH D8KVSI DMKEXT DMKPAG DMKSCN D!KVSP D!KFRE D!KPGT 1!n£g!§ble f§.9!able !1 odul!!! DMKACO DMKCPB DMKDIB DMKNE! D8KTRC DMKALG DMKCPI D!KDRD D!KNES D!KTRD DMKAPI D!KCPS DMKEIG D!KHET D!KTR! DMKATS D!KCPU DMKER! D!KHLD DMKUDR D!KBLD D!KCPV D!KGIO D!KRLE D8KUDU D!KCDB D!KCQG D!KHVD D!KPGS D!KUSO D!KCDI1 DMKCQH D!KIOC D!KRSE D!KVCA D!KCDS D!KCQP D!KIOF D!KSAV D!KVCH D8KCFC DMKCQR D8KIOG D!KSEP D!KVDA D!KCFD D!KCQY D8KIS! D!KSEV D!KVDC D!KCFG D8KCSB D!KJRL D!KSIX D!KVDD D!KCFH D!KCSO DMKLHK D!KSHC D!KVDE D!KCFO D!KCSP DMKLOG D!KSPL D8KVDR D!KCFP DMKCSQ DMKLOH D!KTAP D!KVDS D!KCFS DMKCST DMK!CC D!KTCS D!KVER D!KCFT DMKCSU D!K!ID D!KTDK D!KV!C D!KCKP DMKCSV DMKMHI D!KTHI D!KVMI D!KCKS DMKDEF DMKMOH D!KTRA D!KWR! D!KCLK D!KDIA DMK!SG Figure 16. Executable Modules DATA AREA MODULES In addition to the executable resident and pageable modules (see Figure
16), there are certain modules that only contain data areas and do not
contain executable code. These modules are:
Resident
Module iiiCPE DMKGRW D!KBIO DMKSYS DMKTBL Contents Defines-the end of the CP nucleus
CCW's and data for 3218 model 2A I/O device blocks System constants Terminal translate table 1-80 IBM VM/370 System Logic and Problem Deteraination--Volume 1

Con!~nt.§ output separator table
Bootstrap routines for 3705 Error message data module Error message data module Error message data module Pageable Modul:~ DMKBOX DMKBTS DMKEMA DMKEMB DMKEMC DMKFCB DMKSNT DMKSYM DMKUCB DMKUCS DMKTBM DMKVCC 3203 and 3211 Forms Control Buffer (FCB) load tables System name table System symbol table
3211 Universal Character Set Buffer (UCSB) load tables 1403 Universal Character Set (UCS) load tables Terminal translate tables 3203 Universal Character Set Buffer (UCSB) load tables VIRTUAL TIMER MAINTENANCE The System/370 with EC mode provides
virtual) with four tiaing facilities.
the system
They are: • The interval timer at main storage location X'50' • The time-of-day clock • The tille-of-day clock compara tor • The CPU timer user (both real and
Before describing how CP maintains these timers for virtual machines, it
is necessary to review how VM/370 uses the timing facilities of the real machine. 1. The location X'50' interval timer is used only for time-slicing. 2.
The value placed in the timer is the maximum length of time that
the dispatched virtual machine is allowed to execute.
Because the BLIP function of CMS uses the interval timer (location 1'50'), the uSe of STInER can cause extra blips at the user's
terminal. To avoid extra blips, issue the CftS command SET BLIP OFF. The tiae-of-day clock is used as a time stamp for
enables the scheduler to compute elapsed in-queue
dispatching priority calculation. messages and time for the
3. The time-of-day clock comparator facility is used by CP to schedule timer-driven events for both control program functions and for
virtual machines. A stack of comparator requests is maintained and
as clock comparator interrupts occur, the timer request blocks are
stacked for the dispatcher via calls to DftKSTKIO. 4. The processor timer facility performs three functions: • Accumulates CP overhead • Detects in-queue time slice end • Simulates virtual processor timer The accumulation of CP overhead is accomplished as follows. The VftTTlftE field in the VMBLOK contains the total CP overhead incurred
by the virtual machine; it is initialized to the maximum positive number in a doubleword, X'7PPPPPPF PPFPPlll'. Whenever CP performs CP Introduction 1-81