05-01-2013, 03:41 PM
Memory Management
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Memory managementIdeal memory for a programmer
–Large
–Fast
–Non volatile
–CheapNothing like that → memory hierarchy
–Small amount of fast, expensive memory –cache
–Some medium-speed, medium price main memory
–Gigabytes of slow, cheap disk storageMemory manager handles the memory hierarchy
6Multiprogramming w/ fixed partitionsMultiprogramming –
when one process is waiting for I/O, another one can use the CPUTwo simple approaches
–Split memory in nparts (possible != sizes)
–Single or separate input queues for each partition
–~IBM OS/360 –MFT: Multiprogramming with Fixed number of TasksEECS
Two problems w/ multiprogramming
Relocation and protection
–Don‟t know where program will be loaded in memory
•Address locations of variables & code routines
–Keep a process out of other processes‟ partitionsIBM OS/MFT -modify instructions on the fly; split memory into 2KB blocks & add key/code combinationUse base and limit values (CDC 6600 & Intel 8088)
–address locations + base value →physical address