Review question: process

Consider a hypothetical 32-bit microprocessor that has 32-bit instructions composed of two fields. the first byte contains the opcode and theRemainder an immediate operand or an operand address.

• What is the maximum directly addressable memory capacity (in bytes)?

2(32-8) = 16,777,216 bytes = 16 MB

• Discuss the impact on the system speed if the microprocessor data bus has

• a 32-bit local address bus and a 16-bit local data bus.

Instruction and data transfers would take three bus cycles each - one for the address and two for the data.

• a 16-bit local address bus and a 16-bit local data bus.

Instruction and data transfers would take four bus cycles each - two for the address and two for the data.

• How many bits are needed for the program counter and the instruction register?

24 bits for the PC (24-bit addresses), 32 bits for the IR (32-bit addresses)

In virtually all systems that include dma modules, dma access to main memory is given higher priority than processor access to main memory. why?

If a processor is held up in attempting to read or write memory, usually no damage occurs except a slight loss of time. However, aDMA transfer may be to or from a device that is receiving or sending data in a stream (e.g., disk or network), and cannot be stopped. Thus, if the DMA moduleis held up (denied continuing access to main memory), data will be lost.

Why does a batch system need memory protection? why does a multiprogrammed batch system need memory management and scheduling? why do bothTypes of systems need interrupts?

A batch system needs memory protection so that programs can't modify the monitor.

A multiprogrammed batch system needs memory management so that multiple jobs can be kept in memory at the same time. Memorymanagement will determine which portion of memory each job can use. The system also needs a scheduling algorithm to determine which job can run at any giventime.

Both types of systems need interrupts so that the operating system can regain control of the CPU. A batch system needs this totime-out a long job and a multiprogrammed system needs this to share the processor among the active processes.

What is the purpose of system calls, and how do system calls relate to the operating system and to the concept of dual-mode (kernel mode and userMode) operation?

With a time sharing system, the primary concern is turnaround time. A round-robin scheduler would given every process a chance torun on the CPU for a short time, and reduce the average turnaround time. If the scheduler instead let one job run until completion, then the first job wouldhave a short turnaround time, but later ones would have to wait for a long time.

In a batch system, the primary concern is throughput. In this case, the time spent switching between jobs is wasted, so a moreefficient scheduling algorithm would be first-come, first-served, and let each job run on the processor as long as it wants.

In ibm's mainframe operating system, os/390, one of the major modules in the kernel is the system resource manager (srm). this module isResponsible for the allocation of resources among address spaces (processes). the srm gives os/390 a degree of sophistication unique among operating systems.No other mainframe operating system, and certainly no other type of operating system, can match the functions performed by srm. the concept of resourceIncludes processor, real memory and i/o channels. srm accumulates statistics pertaining to utilization of processor, channel and various key data structures.Its purpose is to provide optimum performance based on performance monitoring and analysis. the installation sets forth various performance objectives, andThese serve as guidance to the srm, which dynamically modifies installation and job performance characteristics based on system utilization. in turn, the srmProvides reports that enable the trained operator to refine the configuration and parameter settings to improve user service.

This problem concerns one example of SRM activity. Real memory is divided into equal-sized blocks called frames, of which there maybe many thousands. Each frame can hold a block of virtual memory referred to as a page. SRM receives control approximately 20 times per second and inspects eachand every page frame. If the page has not been referenced or changed, a counter is incremented by 1. Over time, SRM averages these numbers to determine theaverage number of seconds that a page frame in the system goes untouched. What might be the purpose of this and what action might SRM take?