13.1 silberschatz, galvin and gagne ©2007 operating system concepts with java – 7 th edition, nov...
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13.1 Silberschatz, Galvin and Gagne ©2007Operating System Concepts with Java – 7th Edition, Nov 15, 2006
Quiz
a. Why is LOOK better than SCAN?
Answer the following two questions using exactly one of the words FCFS, SSTF, SCAN, LOOK, C-SCAN, C-LOOK
b. Which algorithm possibly results in starvation? c. Which of SCAN or C-SCAN gives better
throughput?
13.2 Silberschatz, Galvin and Gagne ©2007Operating System Concepts with Java – 7th Edition, Nov 15, 2006
Where is RAID, or is SSTF implemented?
OS* … disk cheap … expensive older … newer serial … parallel (offload work and complexity) logical … physical
volume: logical disk; may span physical disks, or may have several volumes on a physical disk
OS must keep track of physical disks to do * above. Third alternative in middle is possible: OS … controller card (host bus-adapter) … disk
Operating System Concepts with Java – 7th Edition, Nov 15, 2006 Silberschatz, Galvin and Gagne ©2007
Excerpt from Chapter 13
13.4 Silberschatz, Galvin and Gagne ©2007Operating System Concepts with Java – 7th Edition, Nov 15, 2006
How Does Plug and Play (PnP) work?
Reassigns port and maskable interrupt to avoid collision with another device.
Port: device register mapped to small amount of memory to provide control information.
(Contrast: Memory-mapped device, where large amount of memory provides data to or from the hardware.)
MIRQ and NMIRQ wires provide interrupt number, telling what interrupt occurred, provided by the CPU.
(Contrast: Interrupt level, which is a priority set by OS.)
13.5 Silberschatz, Galvin and Gagne ©2007Operating System Concepts with Java – 7th Edition, Nov 15, 2006
Device I/O Port Locations on PCs (partial)
13.6 Silberschatz, Galvin and Gagne ©2007Operating System Concepts with Java – 7th Edition, Nov 15, 2006
Pentium maskable vs. non-maskable interrupts
13.7 Silberschatz, Galvin and Gagne ©2007Operating System Concepts with Java – 7th Edition, Nov 15, 2006
Windows XP Interrupt Request Levels