Program Logic Manual - All about the IBM 1130 Computing System

SECTION 4. COLD START PROGRAMSFLOWCHARTSCold Start Loader: CSTO1Cold Start Program: CSTO2COLD START LOADERThe Cold Start Loader is the one-card bootstrap usedto initiate the operation of the Cold Start Program,which in turn initiates the operation of the monitorsystem.Since it is loaded by the IPL procedure, allinstructions in the Cold Start Loader are in IPLformat. Hence, the program must construct allIOCCs as well as any long instructions requiredby it.The first word set up after entering the programis the second word of the IOCC for reading the ConsoleEntry switches. After this is done, the numberof the physical drive to be assigned as logical drive0 is obtained from the Console Entry switches. Theprogram then checks to see if the number obtainedis valid (0-4, inclusive). If it is not, the programcomes to a WAIT from which the user may restartby entering a valid number and pressing the STARTkey. Once a valid number has been obtained, thedevice code for the drive specified is constructedand saved (for use by the Cold Start Program as wellas the Cold Start Loader).After setting up the second word of the IOCC forsensing the disk (with reset), the program senses thedisk. All bits except the not-ready bit (bit 2) aremasked out. If the drive is not ready, the programcomes to the same WAIT mentioned above.Four long instructions are built, and the finalsteps in the setting up of the IOCC for seeking areperformed. The word count of the Cold Start Programplus the word count of DISKZ plus 27 is storedin DZ000-29, the 27 being the number of wordsreserved in sector @MAD for parameters.After setting up the second word of the IOCCfor reading the disk, the program initiates aseek toward the home position, one cylinder at atime. When the seek is complete, sector zero onthe cylinder currently under the read/write headsis read from the disk„ If no disk error occursduring this read and if the sector address is that ofsector @IDAD, then a branch is made to $ZEND,which is the address of the first word of the ColdStart Program.If the sector address is not that of the Cold StartProgram, another seek toward the home position isinitiated. This seek-and-read process is repeateduntil the proper sector address is found. (Therefore,acartridge with invalid sector addresses causesthe program to function improperly.) Any diskerror results in the program coming to a WAIT witha /3028 in the storage address register.COLD START PROGRAMThe Cold Start Program is fetched from the diskand given control by the Cold Start Loader.Using the same device code that was set up bythe Cold Start Loader for the physical drive assignedas logical drive 0, the Cold Start Programreads the Resident Image into its normal location incore storage. Once this operation is performed,location zero is initialized with an MDX to $DUMP+1and the Auxiliary Supervisor is entered with aparameter of minus 1, causing it to place a dummyJOB monitor control record into the Supervisorbuffer and execute a CALL EXIT.CORE LAYOUTFigure 2, panel 1, shows the layout of the contentsof core storage after the Cold Start Loader has beenloaded and, in turn, has fetched sector @IDAD fromlogical drive 0 into core storage. This sector isread into core such that the DISKZ subroutineresides at DZ000, followed by the Cold Start Program.Figure 2, panel 2, shows the layout of the contentsof core storage after the Cold Start Program hasfetched the Resident Image from sector @RIADfrom logical drive 0 into core storage. TheResident Image, like DISKZ, is fetched in such afashion that all locations occupy their permanentpositions in core storage.Section 4. Cold Start Programs 15