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Wednesday, February 17, 2010
Monday, February 15, 2010
What is Clock Speed?
Clock speed is a measure of how quickly a computer completes basic computations and operations. It is measured as a frequency in hertz, and most commonly refers to the speed of the computer's CPU, or Central Processing Unit. Since the frequency most clock speed measures is very high, the terms megahertz and gigahertz are used. A megahertz is one-million cycles per second, while a gigahertz is one-billion cycles per second. So a computer with a clock speed of 800MHz is running 800,000,000 cycles per second, while a 2.4GHz computer is running 2,400,000,000 cycles per second.
How clock speed should be used as a benchmark of a computer's speed is a matter of some contention, though most chip makers appear to be drifting towards the conclusion that clock speed should be abandoned as the primary value given. The problem comes from the fact that, although clock speed works as a fairly reliable indicator of how one of a company's chips stacks up against another of their chips, it is a poor indicator of how that chip might compete against a different company's chipset. One reason clock speed of the CPU isn't such a reliable test of overall computer speed is that many other factors come into play. The amount of RAM a computer has, the clock speed of that RAM, the clock speed of the front-side bus, and the cache size all play significant roles in determining overall performance.
When comparing one Intel Pentium chip to another Pentium chip, for example, the clock speed is a fairly good indicator of an improvement in speed. An 800Mhz Pentium computer will perform most processor-based tasks roughly twice as quickly as a 400MHz Pentium computer. When comparing a different company's processors, however, the story changes. If we look at both a Pentium chip and an AMD chip, for example, we find that the AMD tends to perform most tasks more quickly than a comparable Pentium. A 1.8GHz AMD chip significantly outperforms a Pentium 1.8Ghz chip, instead performing near the speed of a Pentium 2.2Ghz.
For this reason, AMD stopped listing their clock speed as a primary method of advertising on their computers, instead associating a number with the computer meant to show its performance in comparison to a Pentium. The AMD Athlon 64 3000, for example, has a clock speed of only 1.8GHz, but AMD determined it to be roughly comparable to a Pentium 4 at 3GHz. Intel itself has also begun to move away from the clock speed model of advertising, mostly due to their introduction of a laptop-oriented M line, which has much lower clock speeds to optimize portable performance. By sticking to a clock speed model, Intel made its Pentium-M computers look like they were slow and weak compared to their Pentium 4 models.
While clock speed can still give a general idea of computing power, it is more often recommended these days to look at some sort of trusted benchmark as a way to compare computers. Looking at benchmarks of how various processors handled tasks you care about will give a clearer picture of how the computer will perform for you. One computer might be significantly faster than another at transforming images in a graphic design program, for example, but slower at video-intensive games. This paradigm of more task-specific computer ratings, rather than a focus exclusively on clock speed, ultimately offers consumers a better understanding of what sort of product they can expect.
How clock speed should be used as a benchmark of a computer's speed is a matter of some contention, though most chip makers appear to be drifting towards the conclusion that clock speed should be abandoned as the primary value given. The problem comes from the fact that, although clock speed works as a fairly reliable indicator of how one of a company's chips stacks up against another of their chips, it is a poor indicator of how that chip might compete against a different company's chipset. One reason clock speed of the CPU isn't such a reliable test of overall computer speed is that many other factors come into play. The amount of RAM a computer has, the clock speed of that RAM, the clock speed of the front-side bus, and the cache size all play significant roles in determining overall performance.
When comparing one Intel Pentium chip to another Pentium chip, for example, the clock speed is a fairly good indicator of an improvement in speed. An 800Mhz Pentium computer will perform most processor-based tasks roughly twice as quickly as a 400MHz Pentium computer. When comparing a different company's processors, however, the story changes. If we look at both a Pentium chip and an AMD chip, for example, we find that the AMD tends to perform most tasks more quickly than a comparable Pentium. A 1.8GHz AMD chip significantly outperforms a Pentium 1.8Ghz chip, instead performing near the speed of a Pentium 2.2Ghz.
For this reason, AMD stopped listing their clock speed as a primary method of advertising on their computers, instead associating a number with the computer meant to show its performance in comparison to a Pentium. The AMD Athlon 64 3000, for example, has a clock speed of only 1.8GHz, but AMD determined it to be roughly comparable to a Pentium 4 at 3GHz. Intel itself has also begun to move away from the clock speed model of advertising, mostly due to their introduction of a laptop-oriented M line, which has much lower clock speeds to optimize portable performance. By sticking to a clock speed model, Intel made its Pentium-M computers look like they were slow and weak compared to their Pentium 4 models.
While clock speed can still give a general idea of computing power, it is more often recommended these days to look at some sort of trusted benchmark as a way to compare computers. Looking at benchmarks of how various processors handled tasks you care about will give a clearer picture of how the computer will perform for you. One computer might be significantly faster than another at transforming images in a graphic design program, for example, but slower at video-intensive games. This paradigm of more task-specific computer ratings, rather than a focus exclusively on clock speed, ultimately offers consumers a better understanding of what sort of product they can expect.
microprocessor
A silicon chip that contains a CPU. In the world of personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.
Three basic characteristics differentiate microprocessors:
• Instruction set: The set of instructions that the microprocessor can execute.
• bandwidth : The number of bits processed in a single instruction.
• clock speed : Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.
In both cases, the higher the value, the more powerful the CPU. For example, a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at 25MHz.
In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer)
Three basic characteristics differentiate microprocessors:
• Instruction set: The set of instructions that the microprocessor can execute.
• bandwidth : The number of bits processed in a single instruction.
• clock speed : Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.
In both cases, the higher the value, the more powerful the CPU. For example, a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at 25MHz.
In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer)
CPU
Pronounced as separate letters it is the abbreviation for central processing unit. The CPU is the brains of the computer. Sometimes referred to simply as the central processor, but more commonly called processor, the CPU is where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system.
On large machines, CPUs require one or more printed circuit boards. On personal computers and small workstations, the CPU is housed in a single chip called a microprocessor. Since the 1970's the microprocessor class of CPUs has almost completely overtaken all other CPU implementations.
The CPU itself is an internal component of the computer. Modern CPUs are small and square and contain multiple metallic connectors or pins on the underside. The CPU is inserted directly into a CPU socket, pin side down, on the motherboard. Each motherboard will support only a specific type or range of CPU so you must check the motherboard manufacturer's specifications before attempting to replace or upgrade a CPU. Modern CPUs also have an attached heat sink and small fan that go directly on top of the CPU to help dissipate heat.
Two typical components of a CPU are the following:
• The arithmetic logic unit (ALU), which performs arithmetic and logical operations.
• The control unit (CU), which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.
On large machines, CPUs require one or more printed circuit boards. On personal computers and small workstations, the CPU is housed in a single chip called a microprocessor. Since the 1970's the microprocessor class of CPUs has almost completely overtaken all other CPU implementations.
The CPU itself is an internal component of the computer. Modern CPUs are small and square and contain multiple metallic connectors or pins on the underside. The CPU is inserted directly into a CPU socket, pin side down, on the motherboard. Each motherboard will support only a specific type or range of CPU so you must check the motherboard manufacturer's specifications before attempting to replace or upgrade a CPU. Modern CPUs also have an attached heat sink and small fan that go directly on top of the CPU to help dissipate heat.
Two typical components of a CPU are the following:
• The arithmetic logic unit (ALU), which performs arithmetic and logical operations.
• The control unit (CU), which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.
What is Cache Memory
Pronounced cash, a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent high-speed storage device. Two types of caching are commonly used in personal computers: memory caching and disk caching.
A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.
Some memory caches are built into the architecture of microprocessors. The Intel 80486 microprocessor, for example, contains an 8K memory cache, and the Pentium has a 16K cache. Such internal caches are often called Level 1 (L1) caches. Most modern PCs also come with external cache memory, called Level 2 (L2) caches. These caches sit between the CPU and the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger.
Disk caching works under the same principle as memory caching, but instead of using high-speed SRAM, a disk cache uses conventional main memory. The most recently accessed data from the disk (as well as adjacent sectors) is stored in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of applications, because accessing a byte of data in RAM can be thousands of times faster than accessing a byte on a hard disk.
When data is found in the cache, it is called a cache hit, and the effectiveness of a cache is judged by its hit rate. Many cache systems use a technique known as smart caching, in which the system can recognize certain types of frequently used data. The strategies for determining which information should be kept in the cache constitute some of the more interesting problems in computer science.
A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. Memory caching is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.
Some memory caches are built into the architecture of microprocessors. The Intel 80486 microprocessor, for example, contains an 8K memory cache, and the Pentium has a 16K cache. Such internal caches are often called Level 1 (L1) caches. Most modern PCs also come with external cache memory, called Level 2 (L2) caches. These caches sit between the CPU and the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger.
Disk caching works under the same principle as memory caching, but instead of using high-speed SRAM, a disk cache uses conventional main memory. The most recently accessed data from the disk (as well as adjacent sectors) is stored in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of applications, because accessing a byte of data in RAM can be thousands of times faster than accessing a byte on a hard disk.
When data is found in the cache, it is called a cache hit, and the effectiveness of a cache is judged by its hit rate. Many cache systems use a technique known as smart caching, in which the system can recognize certain types of frequently used data. The strategies for determining which information should be kept in the cache constitute some of the more interesting problems in computer science.
Cache memory
Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory.
Cache memory is sometimes described in levels of closeness and accessibility to the microprocessor. An L1 cache is on the same chip as the microprocessor. (For example, the PowerPC 601 processor has a 32 kilobyte level-1 cache built into its chip.) L2 is usually a separate static RAM (SRAM) chip. The main RAM is usually a dynamic RAM (DRAM) chip.
In addition to cache memory, one can think of RAM itself as a cache of memory for hard disk storage since all of RAM's contents come from the hard disk initially when you turn your computer on and load the operating system (you are loading it into RAM) and later as you start new applications and access new data. RAM can also contain a special area called a disk cache that contains the data most recently read in from the hard disk.
Cache memory is sometimes described in levels of closeness and accessibility to the microprocessor. An L1 cache is on the same chip as the microprocessor. (For example, the PowerPC 601 processor has a 32 kilobyte level-1 cache built into its chip.) L2 is usually a separate static RAM (SRAM) chip. The main RAM is usually a dynamic RAM (DRAM) chip.
In addition to cache memory, one can think of RAM itself as a cache of memory for hard disk storage since all of RAM's contents come from the hard disk initially when you turn your computer on and load the operating system (you are loading it into RAM) and later as you start new applications and access new data. RAM can also contain a special area called a disk cache that contains the data most recently read in from the hard disk.
