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Lecture 11

ITEC 1000 Lecture Notes - Lecture 11: Video Card, Program Counter, Block Diagram


Department
Information Technology
Course Code
ITEC 1000
Professor
Peter Khaiter
Lecture
11

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F13 ITEC 1000A Assignment #3
Assignment #3 Total = 35 marks: 30 marks (Solutions) + 5 marks (HTML
presentation).
Upload Due date: December 5, 11 PM -- No late submissions accepted.
Tasks: the use of a code generator is permitted for this assignment; validation is
not required. Content should be sensibly presented with sufficient
explanation, appropriately formatted.
1. Construct a well-composed single Web Page of your solutions and
explanations of the questions below.
2. Edit the title tag text consisting of the course, section number and your full
name
3. Publish and test your site for functionality -- save as a3.html in
the a3 folder of your remote site.
4. Submit the working URL to your instructor via Moodle Message by the
deadline.
1. As you know, a single CPU processes one instruction at a time. Adding a second
CPU (or core, in current terminology) allows the system to process two instructions
at a time, simultaneously, effectively doubling the processing power of the system. A
third core will offer triple the processing power of a single CPU, and so on.
However, studies have shown that, in general, the expected increase in computing
power starts to decline when the number of cores grows large, beyond eight or so.
Why would you expect this to be the case? For what types of computing problems
might this not be true? [10 marks]
Answers
Computers that have multiple CPU’s within a single computer, sharing some or all
of the system’s memory and I/O facilities, are called MULTIPROCESEEOR
SYSTEMs, or sometimes TIGHTLY COUPLED SYSTEMS. All the processors in a
multiprocessor configuration have access to the same programs and data in shared
memory and to the same I/O devices, so it is possible to divide program execution
between different CPUs.
In practical, increasing the number of CPUs is, in fact, usually effective, although,
as the number of CPU increases, the value of the additional CPUs diminishes because of
the overhead required to distribute the instructions in a useful way among the different
CPUs and the conflicts among the CPUs for shared resources, such as memory I/O and
access to the shared buses. With the exception of certain, specialized systems, there are
rarely more than sixteen CPUs sharing the workload in a multiprocessing computer; more
common today, a multiprocessor might consist of two, four or eight core CPUs within a
single chip. And each core in the chip is a full-blown superscalar CPU.
They are two basic ways of configuring a multiprocessing system. There are
known as MASTER-SLAV MULTIPROCESSING (the mater, manages the system, and

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controls all resources and scheduling. Only the master may execute the operation system.
And the other CPUs are slaves, performing works that are assigned to them by the
master). SYMMTRICAL MULTIPROCESSING (each CUP has identical access to the
operation system, and to all system resources, including memory. Each CPU schedules it
own work, within parameters, constraints, and priorities set by the operation system. )
2. Consider the interrupt that occurs at the completion of a disk transfer. [10 marks]
A) ‘Who is interrupting ‘‘whom’’?
B) Why is the interrupt used in this case? What would be necessary if there were no
interrupt capability on this computer?
C) Describe the steps that take place after the interrupt occurs.
The Data from disk and tapes are transferred only in blocks. These blocks include Gap,
header and the data it’s self, containing zeros and ones. In sublimation to that an interrupt
associated with a disk transfer (read or write operation, to or from a disk system), is
obviously associated with a block of data transfer, done to or from memory.
A. This kind of interruptions is known as IRQ. IRQ meaning Interruption Request from
hardware, in this case the disk. An interruption is a signal to the processor emitted by the
hardware or software (they are two type of interruption, Software and hardware
interruption) indication an event that needs an immediate attention. An interruption alerts
the processor to a high-propriety condition requiring the interruption of the current code
that the processor is executing. In this situation, the disk system is interrupting the
program code that’s running through the microprocessor.
b. The interruption is used in this case to indicate and signal that the block of data is
either 'ready' (RAM) or 'written' (transferred to the disk device), and is used to signify,
that the operation that’s carried out is done. “The service program sends a “ready”
message to the I/O module, again using programmed I/O. At this point, the direct
Memory Access transfer process takes place, outside the control of the CPU, the I/O
service, or the program that requested I/O service. The current application program may
resume execution of the other task, or it may be suspended until the DMA transfer
completes.”
In another view, if there is NO interruption going on, to tell the CPU the next step to be
carried out or execute, it means that there is no proper communication between the
processor and the disk.
Hence the processor cannot obtain the correct guidance on getting the signals what to do
on next (interruption is crustal in this case).
c. As we stated above, in systems programming, an interrupt is considered to be a signal
to the processor discharged by the hardware or software telling the CPU about an action
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