Study On CPU And Memory Hierarchy

Study On CPU And Memory Hierarchy CPU must have compatibility with the memory in the computer system. Memory cannot increase the speed of the processor however it can help the processor increase its performance. If the CPU doesnt get the data it requires, it would sit idle wasting CPU clock cycles that would decrease the overall throughput and execution of the processes. If data needs to be accessed to and from hard disk which is slower as compared to the main memory, more and more cycles are wasted decreasing the efficiency of the system. Conclusion- For better performance of the system, faster program execution and proper CPU utilization the compatibility between CPU and memory is required. A computer employs RAM chips of 256*8 ROM chips of 1024*8. The computer society system needs 2K byte of RAM 4KBYTE of ROM, 4 interface units. Each with 4 registers. A memory mapped I/O configuration is used. The 2 highest order bits of the address bus are connected with address 00 or RAM and 01 for ROM 10 for interface. How many RAM ROM chips are needed? Draw a memory address map. 2 kb of RAM required i.e. 21024(bytes) =2048 bytes (Since 1 kb =1024 bytes) RAM = = 8 chips; and 4kb of ROM is required i.e. 4 x 1024 = 4096 bytes Therefore ROM = = 4 chips; and There are 4 interfaces each having 4 register, So total no. of registers is 44=16 registers; Memory address map Cache Coherence- Caches allow greater performance by storing frequently used data. In multiprocessing system, each processor is provided with its own cache and they all share the same memory or address space so it is possible for more than one processor to access a data item at a time. What if one processor updates the data item without informing the other processors, inconsistencies may result and cause incorrect executions and the problem of inconsistencies is known as Cache Coherence in computing. The coherence of caches is obtained if the following conditions are met. However these read and write operations are said to be one after another and this is not possible due to memory access latency and a write by first processor may not be seen by a read from second processor if the read is made within a very small time after the write has been made. Case 1 Case 2 Processor P1 reads memory location X and then writes back to same location X while no other processor is not accessing the memory location X. Processor P1 reads and then processor P2 writes to and from same location X and currently the location would return value written by processor P2 only. Processor P1 and P2 writes to same memory location X in a sequence and currently the value returned would be decided as per the sequence. Mechanisms- Bus Snooping- In Bus Snooping each cache is connected through the same bus and it is where every CPU knows who has a copy of its cached data. So each CPU watches continually for write activity concerned with data addresses which it has cached. This assumes that all communication can be seen by all. However it is far more complex to implement. Directory Based Approach- In a directory-based system, the data being shared is placed in a common directory that preserves the coherence connecting caches. The directory acts as a filter through which the processor must ask authorization to fill an entry from the primary memory to its cache. When an entry is distorted the directory either updates or invalidates the other caches with that entry. The MESI protocol is the best suited protocol to avoid cache coherence, where M stands for MODIFIED, E stands for EXCLUSIVE, S stands for SHARED and I stands for INVALID. Write Back Cache- Cache uses two approaches to write data back to main memory. Write Through Write Back It is the simplest one in which all write all operations are made to the main memory as well as to cache; ensuring main memory is always valid. Any other CPU- cache module can monitor traffic to main memory to update the data in its own cache, but always results in substantial memory traffic. It minimizes memory writes. In write back method modifications to data in the cache arent copied to the cache source until absolutely necessary. It is also known as copy back cache .In write back updates are made only in the cache. When an update occurs UPDATE bit are set associated with the slot and when the block is replaced it is checked whether the UPDATE bit is set or not. If it is set then data is written back to main memory. For Example- Intel processors since the 80486 uses back caching. Problem with this kind of implementation is that performance improvement comes with a slight threat that data may be vanished if the system crashes and more complex circuitry. Onboard Cache- Cache is a part of multi-level storage strategy which is used to increase the performance of CPU by providing a bridge in between the slower memory RAM and CPU. The cache that is the part of the CPU is known as off-board cache and the cache which is present on the motherboard is known as on-board cache. Generally L1 cache is referred as off-board and L2 is known as on-board. Sometimes L3 cache is also present on the motherboard along with L2. Now a days specific CPU vendors incorporates L2 as a part of CPU and L3 on motherboard. Implementation of Cache- In Cache, latency needs to be decreased and hit rate needs to be increased. Larger caches have better hit rates but longer latency. To address this problem, many computers use multiple levels of cache. The smaller and faster one is L1 cache built inside the CPU known as on-chip. If CPU needs data it first checks in L1; if it hits the processor proceeds at high speed. If the smaller cache misses, the next larger cache (L2) is checked, and so on, before external memory is checked. As the latency difference between main memory and the fastest cache has become larger, some processors have begun to utilize as many as three levels of on-chip cache. For Example- Intels Xeon MP Product code-named Tulsa, AMD Phenom II (2008), Intel Core i7 (2008) uses unified L3 cache. However Cache can be implemented by using Direct Mapped, Associative Mapping or Set-Associative Mapping. Virtual Memory- For the execution of programs memory required is more than what is actually present. So, the technique used to overcome this size limitation is Virtual Memory which is illusion of memory not physically present. The purpose is to allow multiple programs share same memory allowing splitting up of program into smaller pieces that can be loaded into different parts of memory whenever space can be found. Implementation of Virtual Memory- It is implemented using two techniques- one is Demand Paging and other one is Demand Segmentation. CPU generates address which is not physically present. These are the program addresses referred to as logical addresses, they dont have any existence outside the program, the actual memory addresses are known as physical addresses. These virtual addresses are mapped or interchanged to its corresponding physical address through a process known as mapping. A page table or look up table is maintained for this purpose. In Demand paging, valid-invalid bit scheme is used in which a valid-invalid bit is associated with each page. 1 for the page in memory and 0 for not present in memory. During address translation if bit in entry is 0 the page fault occurs. In virtual memory process are divided into chunks of equal size known as pages and chunks of memory in which pages are loaded are known as frames. In Demand Segmentation each row of the lookup table contains a starting address for a logical block of memory, together with the size of the block and a corresponding starting address in physical memory. Paging and Segmentation operates both the same. Problem of Fragmentation- Fixed Memory Partitioning- Operating system occupies fixed portion of main memory and partitions are created for multiple processes but not of same size, so there will be wastage of memory. In most cases the process will not acquire memory provided to it. Variable Memory Partitioning- In variables-size partitions, the memory allocated is as much it is required by process. However when processes are swapped in, small holes are created leading to problem of fragmentation. Compaction is done to solve problem, but it waste CPU time. In Virtual Memory demand paging method is implemented, in which memory is partitioned into equal chunks that are relatively small, and each process is divided into small fixed size chunks of some size. The lists of the frames that are free are maintained by the operating system. As the size of the pages and frames are same so suffer less fragmentation problem. The Memory Hierarchy The design constraints on a computers memory can be summed up by three questions: how much memory is available, how fast it is and how much it will cost? Following are the relationships between these tradeoffs- Smaller access time, greater cost per bit. Greater capacity, smaller cost per bit. Greater capacity, greater access time. Access Time Increase Transfer Rate DecreasesCPU Registers Cache Cost per/bit Decreases Capacity IncreasesRAM Magnetic Disk Figure -Memory Hierarchy Memory hierarchy helps in increasing the performance of processor, without hierarchy, faster process wont help and all time waiting on memory, It provides a large pool of memory that costs as much as the cheap storage near the bottom of the hierarchy, but that serves data to programs at the rate of the fast storage near the top of the hierarchy. It provides a faster access of data stored in the memory. If it is understand how the system moves data up and down the memory hierarchy, then application programs can be written so that data items are stored higher in the hierarchy, where the CPU can access them more quickly. Addressing modes affecting performance of system- It simplifies the memory references, produces variable length instruction format and instruction manipulates operands in memory directly. It adds convenience and flexibility to have modes of addressing, and it allows a large range of addressable memory while using a reasonable number of bits. Addressing modes make it easier to write certain type of programs such as loops that uses an index to address different entries in a table or array. For Example- Indexed Addressing. Now a days computer allows programmer accessible registers that manipulate data directly between registers.

Disadvantage of democracy Essay

The primary disadvantages of democracy are a general lack of accountability, the prospect of personal interest becoming the predominant factor in decisions, and negative financial implications. A democracy lays the power to make decisions in the hands of the majority. This, ironically, places an emphasis on both individual and group power. A group controls the decision-making process, but an influential individual can control the group. The issue with democracy, in spite of the power of the people to control the decision-making process, is that there is no sense of accountability when the group makes a decision that turns out to be a bad one. Even particularly influential individuals in the group who may have persuaded the majority to vote for what led to the bad decision is free from blame because, ultimately, everyone in the group is responsible for his or her choice. In this way democracy, although a group-oriented approach, can become very much about what individuals believe is best for themselves and not for the majority. This type of decision-making also can be very expensive and have negative financial implications. First, a considerable amount of money can be spent in persuading voters to support an idea or cause. Second, voters may embrace an idea or cause, such as lowering taxes, because it sounds ideal when, in practice, it could lead to financial disaster. Disadvantages of Democracy Making the wrong choice In a democratic country, it is the common man who has the supreme right to choose their legislature and their prevailing authorities. As per a general study, not all the people are completely conscious of the political circumstances in their nation. The common masses may not be acquainted of the political matters in their society. This may lead to common man taking an erroneous selection during election. Authorities May Lose focus As the government is bound to changes and modification after each election tenure, the authorities may function with a interim objective. Since they have to go through an election procedure after the conclusion of each tenure, they may lose focus on functioning effectively for the citizens and  instead might concentrate on winning elections. Hordes Have Influence A further disadvantage of democracy is that hordes can manipulate citizens. People may vote in support of a party under the pressure of the bulk. Constrained or influenced by the ideas of those around, an individual may not put across his/her accurate judgment. Democracy averts radicalism and encourages teamwork and synchronization. It also slows things down, stops those in authority doing what they wish regardless of the majority’s desires. Since the military incursion into the Nigerian political scene on January 15, 1966, all the woes of this country are placed on the military. Most Nigerians do not want to hear the word â€Å"military†. They see the military as synonymous with evil. But does the military symbolize evil? Colonel Muamma Gaddafi is a military officer who seized power from the Libyan Monarch in 1969. Colonel Muamma Gaddafi as a military leader, was able to transform Libya to the envy of the world so much that other nationals including Nigerians are queuing at the Libyan embassy for her visa. Under a military leadership in Libya, Nigerians are rushing to the country on a daily basis because the country has a lower inflation of 1% than that of Nigeria which is 20% and a per capita of $8,400 while Nigeria’s per capital is $50. If military regime is synonymous with evil, why are Nigerians running from a country that is under civil rule to a country which is under a military leader? Ghana, our neighbouring West African country was also transformed from a corrupt and poverty stricken nation it was, to a transparent and an accountable nation by a military officer, Flight lieutenant, John Jerry Rawlings. At the moment, Nigerians are running to live in Ghana because the country has improved tremendously in terms of economy and infrastructural development. Ghana has also attained democratic growth and stability having transited from one democratically elected government to another two times. However, let us now compare and contrast the difference between military and civil rules in Nigeria. Nigeria gained independence from Britain on October 1, 1960. Out of the 50 years of Nigeria’s existence as an independent  nation, the military has ruled the country for 29 years. Within the 29 years the military ruled the country, 3 years were used to prosecute the Nigerian civil war, between 1967 to 1970, this means the military actually spent 26 years to rule the country. Out of the 50 years of the nation’s existence, civilians have ruled for 21 years. So, the difference between the years the military have ruled the country and those of civilians nine years. The questions one is asking are, if the military has destroyed the country within the space of 29 years as claimed by the civil leaders, can’t the civil leaders repair it within a space of 21 years? How long does it take to repair what is damaged? What has the civilian leaders be able to remedy since they have been ruling the country? Since Nigeria returned to democracy in 1999, we are still hearing the same old song by politicians, â€Å"You know the military have destroyed the country and you know that it is not easy to repair what has been destroyed†. I find this excuse unacceptable to the Nigerian people because something that was destroyed can be repaired. For instance, Germany, France, Austria etc were devastated during the first and second World War but today they have rebuilt to enviable status. Of all the things the military destroyed, which of them has the civilian leaders been able to put right? Some politicians who are out to deceive the poor masses will say that â€Å"the worst civilian regime is better than military regime.† But is it always true that the worst civilian regime is better than military regime? Politicians are also quick to say that â€Å"at least we can talk now that we are in a civilian regime and that we could not talk during the military administrations.† I found this argument very amusing because our mouths were not muzzled by the military during their administrations. I make bold to say that we spoke more during the military administrations than we do today because then we all saw the military as our common enemy and were united to fight against them. There were so many civil society organizations such as National Democratic Coalition (NADECO) which was headed by late Pa Adekunle Ajasin, Campaign for Democracy headed by late Dr. Beko Ransom Kuti, Civil Liberties Organization headed by former President of Nigerian Bar Association ( NBA ), Olisa Agbakoba (SAN), Afenifere, the Yoruba socio- cultural group headed by late Pa Abraham Adesanya, Association of Senior Staff Union of Uni versities, headed by the INEC Chairman, Professor Atahiru Jega, Petroleum and Natural Gas Senior Staff Association of Nigeria (PENGASSAN ), headed by Chief Frank Ovie Kokori etc. These civil society groups spoke openly against the ills of the military and sent them back to the barracks. At that time too, journalists engaged in revolutionary journalism which made the press very vibrant and added impetus to the voice of the masses. During the military era, television and radio stations were mostly owned by both states and the federal governments. DAAR communications, owner of African Independent Television and Ray power Radio station and Minaj television and FM radio station which started in 1994 were the only privately owned broadcast organizations in the country, the rest belonged to both the states and federal governments. Would the governments have allowed the masses to use their media to criticize them? There is no government that allows such a thing in any part of the world. Let us assume that we did not talk during military administrations, what have we achieved since 1999 that we have been talking? Have those who claimed to be representing us both in th e State Houses of Assembly and the National Assembly ever taken our advise? We said the National Assembly should pass the Freedom of Information Bill into law, have they done it since it was introduced into the house? We said the Justice Mohammed Uwais recommendations on Electoral Reform be adopted by the National Assembly, have they adopted them? The Federal Government has earmarked #6.6 billion towards the celebration of Nigeria’s 50th anniversary, which the masses condemned in totality, yet the Federal Government is bent on wasting such amount of money on the celebration of failure. Will the States and Federal Governments ever listen to the masses? We said the huge allowances our so call representatives are receiving should be reduced, did they agree to reduce their allowances? A senator receives #45 million allowance quarterly, while each member of the House of Representatives receives #27.2 million allowance quarterly. Each senator receives #500 million constituency development allowance yearly which is not accounted for. Their salaries and other benefits are not included these allowances. Is there justification for such huge allowances considering the fact that they sit for 180 days in a year? Can we say with a sense of pride that the lives of Nigerians have improved positively since we returned to democracy in 1999? Let me make it clear that democracy is not just about having freedom to talk, it goes beyond mere talking. Democracy is about quality leadership that translates  into accelerated development and growth in all areas of human aspirations. Democracy goes beyond just having civilians in government. Any administration, be it military or civil government that cannot better or improve the lives of the people is a monumental failure. The main purpose of governance is to coordinate and harness the wealth of the people for an effective development that will enhance the standard of living of the people. Have we seen such achievements and development since 1999? Let us compare and contrast civil administrations since 1999 till date and military administrations from 1985 till 1999 when the military handed over the reins of power to civilians. We shall start this comparison with the economy. Before the civilians took over government in 1999, a 50 kg bag of rice was sold for N2,500, today it is selling for N8,000. A small bag of beans that was sold for N1,800, now sells for as much as N7,000. Is this not outrageous. Before the commencement of the Obasanjo’s regime in 1999, Nigerians were able to eat twice daily. Morning and night, which was popularly called one –zero-one. At present, most Nigerians eat once daily, which is popularly called zero – one- zero. Is this not regression? If the agricultural sector is well funded and productive, why are prices of foodstuffs on the increase? The unemployment rate has gone up drastically because many industries are closing down while some are relocating to our neighbouring countries due to lack of regular supply of electricity. The Obasanjo’s regime in 1999, inherited 3,500 megawatts of electricity from the military, today it has reduced to a mere 2,500 megawatts for a population of 150 million people. The problems of industries and other organizations that consume large quantity of electricity are compounded as a result of the high cost of petroleum products such as petrol and diesel. These products are used to power generators which provide alternative power for industries. As at the time Nigeria return to democracy in 1999, the prices of petroleum product were cheap. But before ex-president Olusegun Obasanjo, who also doubled as petroleum minister, left office in 2007, he had increased the prices of these products eleven times. A litre of kerosene that cost N9.00 in 1999, now sells for N125.00. Petrol that cost N11.00 at that time, now goes for N65.00 while diesel that cost N10.00 then now sells for N120 per litre.

Formation of a Company Essay

Refers to the entire process by which a company is brought into existence. It starts with the conceptualisation of the birth a a company and determination of the purpose for which it is to be formed. The persons who conceive the company and invest the initial funds are known as the promoters of the company. The promoters enter into preliminary contracts with vendors and make arrangements for the preparation, advertisement and the circulation of prospectus and placement of capital. However, a person who merely acts in his professional capacity on behalf of the promoter (eg lawyer, CA, etc) for drawing up the agreement or other documents or prepares the figures on behalf of the promoter and who is paid by the promoter is not a promoter. The promoters have certain basic duties towards the company formed :- In case of default on the part of the promoter in fulfilling the above duties, the company may :- A promoter may be rewarded by the company for efforts undertaken by him in forming the company in several ways. The more common ones are :- If the promoter fails to disclose the profit made by him in course of promotion or knowingly makes a false statement in the prospectus whereby the person relying on that statement makes a loss, he will be liable to make good the loss suffered by that other person. The promoter is liable for untrue statements made in the prospectus. A person who subscribes for any shares or debenture in the company on the faith of the untrue statement contained in the prospectus can sue the promoter for the loss or damages sustained by him as the result of such untrue statement. II. Incorporation by Registration : The promoters must make a decision regarding the type of company i. e a pulic company or a private company or an unlimited company, etc and accordingly prepare the documents for incorporation of the company. In this connection the Memorandum and Articles of Association (MA & AA) are crucial documents to be prepared. Memorandum of Association of a company : Is the constitution or charter of the company and contains the powers of the company. No company can be registered under the Companies Act, 1956 without the memorandum of association. Under Section 2(28) of the Companies Act, 1956 the memorandum means the memorandum of association of the company as originally framed or as altered from time to time in pursuance with any of the previous companies law or the Companies Act, 1956. The memorandum of association should be in any of the one form specified in the tables B,C,D and E of Schedule 1 to the Companies Act, 1956. Form in Table B is applicable in case of companies limited by the shares , form in Table C is applicable to the companies limited by guarantee and not having share capital, form in Table D is applicable to company limited by guarantee and having a share capital whereas form in table E is applicable to unlimited companies. Contents of Memorandum : The memorandum of association of every company must contain the following clauses :- Name clause The name of the company is mentioned in the name clause. A public limited company must end with the word ‘Limited’ and a private limited company must end with the words ‘Private Limited’. The company cannot have a name which in the opinion of the Central Government is undesirable. A name which is identical with or the nearly resembles the name of another company in existence will not be allowed. A company cannot use a name which is prohibited under the Names and Emblems (Prevntion of Misuse Act, 1950 or use a name suggestive of connection to government or State patronage. Domicile clause The state in which the registered office of company is to be situated is mentioned in this clause. If it is not possible to state the exact location of the registered office, the company must state it provide the exact address either on the day on which commences to carry on its business or within 30 days from the date of incorporation of the company, whichever is earlier. Notice in form no 18 must be given to the Registrar of Comapnies within 30 days of the date of incorporation of the company. Similarly, any change in the registered office must also be intimated in form no 18 to the Registrar of Companies within 30 days. The registered office of the company is the official address of the company where the statutory books and records must be normally be kept. Every company must affix or paint its name and address of its registered office on the outside of the every office or place at which its activities are carried on in. The name must be written in one of the local languages and in English. Objects clause This clause is the most important clause of the company. It specifies the activities which a company can carry on and which activities it cannot carry on. The company cannot carry on any activity which is not authorised by its MA. This clause must specify :- In case of the companies other than trading corporations whose objects are not confined to one state, the states to whose territories the objects of the company extend must be specified. Consequences of an ultravires transaction :- However, the doctrine of ultra-vires does not apply in the following cases :- The following are exceptions to the rule of limited liability of members :- Capital clause The amount of share capital with which the company is to be registered divided into shares must be specified giving details of the number of shares and types of shares. A company cannot issue share capital greater than the maximum amount of share capital mentioned in this clause without altering the memorandum. Association clause A declaration by the persons for subscribing to the Memorandum that they desire to form into a company and agree to take the shares place against their respective name must be given by the promoters. Articles of Association The Articles of Association (AA) contain the rules and regulations of the internal management of the company. The AA is nothing but a contract between the company and its members and also between the members themselves that they shall abide by the rules and regulations of internal management of the company specified in the AA. It specifies the rights and duties of the members and directors. The provisions of the AA must not be in conflict with the provisions of the MA. In case such a conflict arises, the MA will prevail. Normally, every company has its own AA. However, if a company does not have its own AA, the model AA specified in Schedule I – Table A will apply. A company may adopt any of the model forms of AA, with or without modifications. The articles of association should be in any of the one form specified in the tables B,C,D and E of Schedule 1 to the Companies Act, 1956. Form in Table B is applicable in case of companies limited by the shares , form in Table C is applicable to the companies limited by guarantee and not having share capital, form in Table D is applicable to company limited by guarantee and having a share capital whereas form in table E is applicable to unlimited companies. However, a private company must have its own AA. The important items covered by the AA include :- Alteration of articles of association : A company can alter any of the provisions of its AA, subject to provisions of the Companies Act and subject to the conditions contained in the Memorandum of association of the company. A company, by special resolution at a general meeting of members, alter its articles provided that such alteration does not have the effect of converting a public limited company into a private company unless it has been approved by the Central Government. The articles must be printed, divided into paragraphs and numbered consequently and must be signed by each subscriber to the Memorandum of Association who shall add his address, description and occupation in presence of at least one witness who must attest the signature and likewise add his address, description and occupation. The articles of association of the company when registered bind the company and the members thereof to the same extent as if it was signed by the company and by each member. III. Registration of the Company Once the documents have been prepared, vetted, stamped and signed, they must be filed with the Registrar of Companies for incorporating the Company. The following documents must be filed in this connection :- {text:list-item} {text:list-item} {text:list-item} Certificate of Incorporation Once all the above documents have been filed and they are found to be in order, the Registrar of Companies will issue Certificate of Incorporation of the Company. This document is the birth certificate of the company and is proof of the existence of the company. Once, this certificate is issued, the company cannot cease its existence unless it is dissolved by order of the Court. IV. Commencement of Business A private company or a company having no share capital can commence its business immediately after it has been incorporated. However, other companies can commence their activities only after they have obtained Certificate of Commencement of Business. For this purpose, the following additional formalities have to be complied with :- If a company has share capital and has issued a prospectus, then :- {text:list-item} {text:list-item} {text:list-item} {text:list-item} {text:list-item} {text:list-item} {text:list-item} Once the above provisions have been complied with, the Registrar of Companies grants â€Å"Certificate of Commencement of Business† after which the company can commence its activities

The Rising Price Of The American Social Contract - 1204 Words

Many of the protesters occupying Wall Street and other places say they are upset about the rising price of going to college. There is little dispute today that the number of students who have debt has increased, and that the amount of money they have borrowed has gone up (Billitteri). Many students incur large amounts of debt that will never pay dividends in higher wages or greater job satisfaction, and they graduate into a world with weak employment prospects. It s a betrayal of the American social contract that says if you work hard and invest in yourself through education, you ll be able to build a better life. The current system is badly in need of an overhaul, and this paper will present several ways to bring about this needed†¦show more content†¦In the 1980s it covered about half; in the 1970s it covered more than 70 percent. (Abramson). The reality is that for young people today, it is harder to educate one s way into the middle class, and college costs are leaving many in this generation without the credentials they need to thrive in the 21st century economy. One radical solution that recently has been proposed is that the federal government should completely cancel student loan debt to stimulate the economy (Caffentzis, 31). However, history has shown that in the case of tax rebate checks, people tend to spend any rebates to pay off other existing debt, or they simply save them. This does little to stimulate the economy, and one suspects that the same would happen with across-the-board loan forgiveness (_Harris_). However, there are several measures that can be taken to make college more affordable. Let s start with the student loan and grant system. The government should increase the number of need-based Pell Grants awarded to students, but there should also be more grant money given to the students willing to chose a cheaper public college or start their academic career by attending community college. Most colleges would consequently want to keep their tuition costs low to remain attractive to prospective students. This goes hand in hand with the fact that administration