1) a) Name the components of CPU

b.What is the purpose of Instruction Decoder?

c. What is program counter?

d.What is an address bus? 

e.What are the possible threats to a computer system and how to provide security?

f.Explain the typical causes of computer failures.

g.What is the function of MDR / MBR?

1.a.Name the components of CPU

Unit of arithmetic logic
The computer's arithmetic and logical operations are handled by the arithmetic logic unit (ALU). Two registers (A and B) are used to store input data for an operation, while the accumulator is used to store output. This register carries the ALU's instructionsinstruction .'s

The A register and the B register are used, for example, when adding two numbers to a calculator. In the accumulator, the ALU executes the addition and stores the result. In a logical operation, the input registers are filled with the data to be compared. The accumulator holds the outcome of the comparison, which is either a 1 or 0. The accumulator's contents are then written to the cache location reserved by the program for the result, regardless of whether the operation is logical or arithmetic.

In addition, the ALU performs yet another function. There is a memory region to begin loading instructions based on the result of this calculation. An instruction pointer register entry is created to store the result.

a pointer and an instruction register
It is the position of the next instruction that will be executed by the CPU that is specified by the instruction pointer. Memory location pointing to a new instruction is loaded into a register after each execution of a previously executed instruction is complete, as seen in this example.

Instruction register points are increased one instruction address once the instruction has been placed into the instruction register. For this to be done successfully, it must be incremented by one.

Cache

 Memory is never accessed directly by the CPU. Caches are now commonplace in modern CPUs. Data can be fed to the CPU far faster than it can be processed by the CPU. There are several reasons for this, but I'll go into more detail in the following piece.

Because it is on the processor chip, cache memory is both faster and closer to the CPU than system RAM. In order to keep the CPU from having to wait for data to be fetched from RAM, the cache provides data storage and instructions for the CPU. Whenever the CPU wants data, the cache checks to see if the data is already in residence and then provides it to the CPU.

Data is retrieved from RAM if it is not in the cache and predictive techniques are used to shift additional RAM into the cache. An analysis of what is requested is performed by the cache controller in order to determine what further data is needed from RAM. It prepares the cache for the incoming data. In order to keep the CPU active and not waste time waiting for data, a cache that is faster than RAM might be used.

Three levels of cache are built into our basic CPU. These two levels are intended to anticipate what data and instructions will be needed next and shift them from RAM to the CPU as close as possible so that they are readily available when required. Depending on the processor's speed and intended purpose, cache sizes can range from 1 MB to 32 MB.

There is a Level 1 cache right next to the processor. There are two kinds of L1 cache in our CPU. There is an instruction cache and a data cache in L1i and L1d, respectively. From 64KB to 512KB are typical levels 1 cache sizes.

Control and monitoring software for a computer's memory(memory management)
The data flow between RAM and the CPU is managed by the memory management unit (MMU). Virtual memory addresses can also be converted to physical locations, which is necessary in multitasking situations.

The CPU's clock and control unit.
To ensure seamless operation, all of the CPU's components must be timed in sync. Using timing signals that reach throughout the CPU, the control unit performs this function at a rate set by the clock speed.

Random Access Memory (RAM)
Even though it's displayed in this diagram and the following, RAM (the main storage) isn't actually part of the CPU. Its job is to keep data and programs in a ready-to-use state for when the CPU calls for them.

 

b.What is the purpose of Instruction Decoder?

The instruction decoder in a processor is a combinatorial circuit that can be either a read-only memory or a regular combinatorial circuit. Its job is to translate an instruction code into the address in micro memory where the instruction code starts.

The Plan of Action After that, the decoder reads the next instruction from memory and dispatches its components to their proper locations.

The control unit generates the pulse sequences required to implement each machine-language command on each control signal (and to fetch the next instruction).

Many of those control signals can be "directly decoded" from the instruction register if you're lucky. The instruction register's IR output bits, for example, can be wired directly to the ALU's "which function" inputs. If the ALU does a bogus SUBTRACT while the rest of the processor executes a STORE command, that's fine.

Any residual control signals that cannot be deciphered from the instruction register are generated by a [Moore machine] or a [Mealy machine]. There are numerous approaches to implement the control unit.

If you're making a Princeton processor (which obtains instructions from the same single-ported memory that reads and writes data), LOAD and STORE must require more than one clock cycle. (One for data, and another for reading the next instruction.) This holds true for a wide range of processors, including simple Harvard architecture computers and complicated high-performance processors with a separate instruction cache.

 

c. What is program counter?

This is a CPU register that holds the next instruction to be performed from memory, and it is called a program counter (PC). Faster job completion and tracking of where the process is in its execution are both made possible by this digital counter.

It is also known as an instruction counter, instruction pointer, instruction address register, or sequence control register.

Memory has a unique address for each instruction and each piece of data. The software application in charge of processing each instruction increments the program counter with the address of the next instruction to be fetched. As part of the execution cycle/standard fetch, the program counter transfers this information to the memory address register. When the next instruction is fetched, the program counter increments by one. The program counter normally resets to zero when the machine is restarted or reset.

Every binary latch in the program counter corresponds to a single bit in the computer's program counter. Using the program counter and other registers, the current instruction is identified. There are instructions for modifying or jumping to this location. Jump and branch instructions can be used to access and modify the PC. As a result, branch instructions can be used to load the destination address into the program counter. The data processing instructions can also be used to load the address into the program counter.

 

d.What is an address bus? 

 

An address bus is a computer bus design for transferring data between devices defined by the physical memory's hardware address (the physical address), which is recorded in binary integers to allow the data bus to access memory storage.

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Using the address bus, the CPU or a DMA-capable device can determine the physical address and send read/write orders to the memory. Bits are used to read and write all address busses by the CPU or DMA.

In order to reduce costs and improve modularity, the system bus architecture was designed. Rather than using a single bus for all of a computer's functions, most modern computers use many buses.

The address bus, data bus, and control bus are all components of a computer system's system bus, which connects the essential components of a computer system.

The quantity of memory that can be accessed by a system is how an address bus is evaluated. A 32-bit address bus allows a system to access 4 gibibytes of memory space. With a 64-bit address bus and a supported operating system, newer computers can address up to 16 exbibytes of memory, making them nearly limitless in terms of memory access.

 

e.What are the possible threats to a computer system and how to provide security?

 

Threats to Computer Security

Threats to computer security include Trojans, viruses, adware, malware, rootkits, hackers, and more. Check out the most dangerous computer security threats.
Computer Viruses
Malicious software that multiplies itself and infects the files and programs on your computer, rendering them inoperable.
computer worms
Computer worms exploit the network to deliver copies of harmful malware to other PCs. It can also send and receive documents using the user's email.
Scareware
It displays false virus notifications to lure users into buying software. False malware pop-ups may appear on a scareware infected PC, prompting users to buy a fake anti-virus program.
Keylogger
Keyloggers can monitor a user's computer activity in real-time. Keyloggers run in the background, recording all keystrokes and sending them to hackers to steal passwords and banking information.
Rootkit
A rootkit is a malicious program that masquerades as genuine files to deceive the computer user. Rootkits disguise viruses and worms as required files. Rootkits are tough to remove and only an antivirus with anti-rootkit capability can do it.

 

 How to provide security?

Anti-virus software should be installed.

Ensure that all PCs have trustworthy anti-virus software installed. All servers, PCs, and laptops should be included. If employees use computers at home for work or to connect to the network remotely, anti-virus software should be installed.

Check to see if your anti-virus software is up to date.

Every day, new computer viruses are published, and it is critical that organizations maintain their anti-virus software up to date to defend themselves from these threats. Companies should consider regulations that prevent computers from connecting to the network unless they have the most up-to-date anti-virus software installed.

To safeguard networks, use a firewall.
Because computer viruses can spread by methods other than email, it's critical to install a firewall to prevent unauthorized traffic from accessing the network. A personal firewall should be established to ensure that users who use computers for business away from the security of the company's network, such as home PCs or laptops, are protected.

All email traffic should be filtered.
Computer viruses should be filtered out of all incoming and outgoing email. To avoid computer infections, this filter should be placed at the network's perimeter. Emails with particular file attachments, such as.EXE,.COM, and.SCR files, that are typically used by computer viruses to spread themselves, should also be blocked from entering the network.

All users should be taught to be wary of strange e-mails.

Ensure that all users are aware of the importance of never opening an attachment or clicking on a link in an email they did not expect. Even if the email comes from a trusted source, use caution when opening attachments or clicking links in emails. Criminals take advantage of your trust in a known email contact to deceive you into clicking on a link or attachment.

Examine any downloaded files from the internet.

Before using any files downloaded from the Internet, make sure they've been screened for viruses. To guarantee that all files are properly scanned, this scanning should ideally be done from a single central location on the network.

Run programs from unknown sources with caution.

It is critical that you obtain your software from a reliable source. This is to ensure that all software installed can be traced back to its source and that its legitimacy can be verified. Aside from ensuring that the proper licensing agreements are in place, working with a reputable vendor can help limit the chance of virus-infected software damaging your company. All users should be taught not to run a computer software unless the source is known or has come from a reputable person or company.

Create a vulnerability management strategy.

The majority of computer viruses and worms attempt to take advantage of flaws and vulnerabilities in the operating system and programs that businesses utilize. Every day, new vulnerabilities are introduced into networks, whether as a result of the installation of new software and services, the modification of existing systems, or the discovery of previously unknown flaws. It's critical to check your network and the programs that operate on it for new vulnerabilities on a frequent basis. Any uncovered vulnerabilities should be prioritized and rated in terms of their criticality and potential commercial effect. After that, devise a strategy for dealing with the vulnerabilities, whether by patching, updating, or controlling the vulnerability using tools like firewalls or Intrusion Detection Systems.

Back up crucial data on a regular basis.

To ensure that you have a reliable source of data in the event that your network is compromised with a computer virus, make regular copies of key files on removable media such as portable drives or tape. Backups will not only ensure that essential data is available in the event that a computer virus infects the firm's network; they will also allow the company to restore systems to software that is known to be virus-free. You should keep these backups safely offsite for enhanced security. That way, if the firm suffers a catastrophic setback, such as the building catching fire, the data will be protected in a secure offsite location and may be swiftly restored in a new location.

Create a policy for information security.

The design and dissemination of an Information Security Policy is vital in ensuring that information security is given the attention it deserves inside the organization, and it is the first and most important step in securing the company's systems and data. It's critical that senior management backs the Information Security Policy, and that all users understand their roles and obligations under it.
Keep an eye on the logs and systems.

f . Explain the typical causes of computer failures.

Spike in voltage -

This is a brief interruption in the supply of electricity. It's vital to understand that transients can last anywhere from a few milliseconds to several minutes. Even a minor power outage can cause a computer to malfunction and corrupt data. If your screen goes black during a thunderstorm, it's most likely due to a voltage spike.

The normal scenario is that a circuit board dies with no obvious signs of damage, and the computer goes down. The failure is assumed to be caused by a faulty circuit board, but a check reveals no signs of physical damage. The operation is resumed after a replacement board is fitted.

Failure to update software - Computer software frequently has bugs or vulnerabilities. These are merely code errors, but they can expose the software to viruses and malfunctions. When a bug is found, the software designer issues a "patch" that must be downloaded and rebooted. Failure to upgrade the program by installing the patch can result in data corruption.

Failure to maintain virus protection up to date - Malware protection products for computer rooms and data centers are available. The subscription must be kept up to date once it has been installed. Slow data processing is one of the telltale signs of a malware-infected machine.

Insufficient cooling - Computers generate heat, and the more data they process, the more heat they generate. Excessive heat causes servers, the "brains" of computers, to fail, hence appropriate cooling is required.

Environment - If a computer room has its own cooling system, it may be possible to regulate the temperature more precisely. When the cooling is shared with other equipment or the space includes offices, the task becomes more difficult. People have different comfort requirements than machines.

Power outage, PDU failure - Power Distribution Units (PDUs) in homes and offices are comparable to power bars. They are commonly found adjacent to the server racks and distribute electricity to various components in a computer room. PDUs have a variety of issues. Receptacles corrode and wear out, causing faulty connections. Moisture can also cause corrosion.

Uninterruptible Power Supply (UPS) batteries - UPS batteries are prevalent in computer rooms. During an outage, they are most commonly utilized to provide continuous power for a limited duration. The life expectancy of a "10 year life" battery might be as short as 4-5 years depending on how it is used and the architecture of the battery. Any battery's life will be shortened if the room temperature is too hot. Even a tiny business like a dentist's office relies on UPS batteries.

Defective transfer switch battery - This could indicate that the facility doesn't have a good battery maintenance program in place. It could also indicate that the transfer switch has become "locked" in place. Preventative maintenance might be able to help you avoid a breakdown.
Failure to synchronize (come on line) standby power - When the grid's electric power goes out, standby power takes over in one of two ways. The goal of a small computer room is to turn computers off in a controlled manner. A fully charged UPS will provide enough power for a computer to preserve its data and shut down for 10-15 minutes. In a larger facility, it's a question of keeping cooling and power running long enough for the backup generator to "synchronize," or get up to a speed fast enough to power the infrastructure and keep data processing going.

 

g.What is the function of MDR / MBR?

Any information sent to or received from an immediate access storage device is stored in the CPU's memory buffer register, also known as the memory data register (MDR). The memory address register includes a duplicate of the value in the specified memory location. Minor changes in the operation of the processor and memory units are not influenced by this buffer. As soon as a data item is written to the MBR, it is ready to be read or written back into main memory at any time during the next clock cycle.

Data from memory is stored in this register and can be moved between components or from one component to another. It is necessary to transfer a word to the MBR before it can be placed in the correct location in memory, and arithmetic data that has to be processed in the ALU must first be transferred to the MBR before being stored in the accumulation register and then processed in the ALU.

In other words, the MDR is a register that works both ways. As soon as the memory is accessed and the MDR is accessed, the data is written in one direction and only one direction. Memory Data Register (MDR) is used to store the data that will be written to memory when a write instruction is issued by a CPU.

The memory address register and memory data register form a simple interface between computer storage and a microprogram (MAR).