computer science essay
06-18, 2015
RAM是指随机存取存储器，是所有计算机中都有的一种数据存储。它为电脑提供了读/写空间，存入CPU(中央处理器)中。内存的主要目的是为了存储临时数据和指令所需的常规操作，加快CPU的存取时间。RAM是一个不稳定的内存,所以一旦关闭电源，存储指令和数据会丢失。
随机存取存储器是如何让工作的—How RAM works
RAM是“随机存取”，因为您可以一如既往的访问任何存储单元，如果你能辨别相交的行和列单元。在RAM中，存储单元可以以任意顺序访问。
动态随机存取存储器(DRAM)是最常见的计算机内存，晶体管和电容配对形成记忆细胞代表一位的数据。晶体管像开关一样控制电路，使内存芯片阅读电容器或更改其状态。与此同时，电容器包含信息0或1。
RAM stands for Random Access Memory which is a type of data storage used in all computers. It provides space to your computer to read/write to be accessed by the CPU (Central Processing Unit). The main purpose of RAM is to store temporary data and instructions required for it regular operation, resulting in faster access time for the CPU. RAM is a volatile memory, so stored instructions and data are lost once the power is turned off.
随机存取存储器是如何让工作的—How RAM works
RAM is considered "random access" because you can access any memory cell unswervingly if you can identify the row and column that intersect at that cell. Memory cells in RAM can be accessed in any order.
The most common form of computer memory which is the Dynamic RAM (DRAM), a transistor and a capacitor are paired to form a memory cell representing a single bit of data. The transistor operates as a switch that enables the control circuitry on the memory chip to read the capacitor or changes its state. Meanwhile, the capacitor contains the bits of information 0 or 1.
A capacitor is similar to a small bucket that is capable of storing electron. The bucket is filled with electrons by storing a 1 in the memory cell and it is emptied by storing a 0. The problem with the capacitor bucket is that it has a leak, thus for dynamic memory to work, either the CPU or the memory controller has to proceed and recharge all of the capacitors containing a 1 before they release. By doing this, the memory controller reads the memory and then writes it back, resulting in the refresh operations taking place repeatedly thousands of times per second.
DRAM works by transferring a charge through the appropriate column to turn on the transistor at each bit in the column. The row lines hold the state capacitor should take on when writing, while the sense-amplifier decides the level of charge in the capacitor when reading. If it is more than 50%, it reads as 1; else, it reads as 0.#p#分页标题#e#
Static RAM uses a completely different technology. The main difference is it never has to be refreshed which make SRAM a lot faster than DRAM. Furthermore, Static RAM is faster and expensive whereas DRAM is opposite. Therefore, SRAM is used to make CPU's speed sensitive cache, while DRAM forms the larger system RAM space.
随机存取存储器的类型—Types of RAM
SRAM (Static RAM)
Static RAM also known as SRAM is the first type of RAM and it does not need to be refresh. SRAM can be accessed at around 10 nanoseconds. SRAM is more costly and may require up to four times the size for a given amount of data than DRAM. The structure of SRAM restricts them to maximum data capacity of 256kb, therefore, SRAM is used in system cache.
DRAM (Dynamic RAM)
DRAM was created to overcome the restriction of SRAM. Even though, DRAM chips provide much slower access time compare to SRAM, it can store several megabytes of data on a single chip. DRAM stores each bit of data in a separate capacitor inside an integrated circuit and need to be refresh periodically. However, with the constant refresh, it can make access even much slower and causes the DRAM chips to draw extra power from the computer. Thereafter, DRAM is used as main memory in the computer because of it high capacity and low cost.
EDO RAM (Extended Data Output RAM)
EDO RAM is the leading RAM in the mid-1900s. When one piece of data is being sent to the processer, another is being retrieved from the RAM module. The usual accessed time for EDO DRAM is 60 ns.
SDRAM (Synchronous DRAM)
SDRAM is around twice as fast as EDO RAM because it is able to run the speed at the speed of the system bus (up to 100-133 MHz). Besides, SDRAM allow new memory access before the proceeding access is accomplished.
RDRAM (Rambus RAM)
The name Rambus originated from a company named Rambus Inc that manufactured it and RDRAM has a data transfer rate of 800MHz. RDRAM can only used in computers with special RDRAM channels and slots.
DDR RAM (Double-data Rate RAM)
DDR RAM is used to replace SDRAM which it can double the rate speed at which standard SDRAM can process. The data transfer rate of DDR RAM is between 100 and 200MHz.
DDR RAM
DDR2 RAM
DDR2 RAM is the newer version of DDR RAM. The data transfer rate is between 200 and 400MHz. the significant features in DDR2 RAM are higher speed, density and require lower power than DDR RAM.
随机存取存储器是如何让工作的—How RAM works
RAM是“随机存取”，因为您可以一如既往的访问任何存储单元，如果你能辨别相交的行和列单元。在RAM中，存储单元可以以任意顺序访问。
动态随机存取存储器(DRAM)是最常见的计算机内存，晶体管和电容配对形成记忆细胞代表一位的数据。晶体管像开关一样控制电路，使内存芯片阅读电容器或更改其状态。与此同时，电容器包含信息0或1。
RAM stands for Random Access Memory which is a type of data storage used in all computers. It provides space to your computer to read/write to be accessed by the CPU (Central Processing Unit). The main purpose of RAM is to store temporary data and instructions required for it regular operation, resulting in faster access time for the CPU. RAM is a volatile memory, so stored instructions and data are lost once the power is turned off.
随机存取存储器是如何让工作的—How RAM works
RAM is considered "random access" because you can access any memory cell unswervingly if you can identify the row and column that intersect at that cell. Memory cells in RAM can be accessed in any order.
The most common form of computer memory which is the Dynamic RAM (DRAM), a transistor and a capacitor are paired to form a memory cell representing a single bit of data. The transistor operates as a switch that enables the control circuitry on the memory chip to read the capacitor or changes its state. Meanwhile, the capacitor contains the bits of information 0 or 1.
A capacitor is similar to a small bucket that is capable of storing electron. The bucket is filled with electrons by storing a 1 in the memory cell and it is emptied by storing a 0. The problem with the capacitor bucket is that it has a leak, thus for dynamic memory to work, either the CPU or the memory controller has to proceed and recharge all of the capacitors containing a 1 before they release. By doing this, the memory controller reads the memory and then writes it back, resulting in the refresh operations taking place repeatedly thousands of times per second.
DRAM works by transferring a charge through the appropriate column to turn on the transistor at each bit in the column. The row lines hold the state capacitor should take on when writing, while the sense-amplifier decides the level of charge in the capacitor when reading. If it is more than 50%, it reads as 1; else, it reads as 0.#p#分页标题#e#
Static RAM uses a completely different technology. The main difference is it never has to be refreshed which make SRAM a lot faster than DRAM. Furthermore, Static RAM is faster and expensive whereas DRAM is opposite. Therefore, SRAM is used to make CPU's speed sensitive cache, while DRAM forms the larger system RAM space.
随机存取存储器的类型—Types of RAM
SRAM (Static RAM)
Static RAM also known as SRAM is the first type of RAM and it does not need to be refresh. SRAM can be accessed at around 10 nanoseconds. SRAM is more costly and may require up to four times the size for a given amount of data than DRAM. The structure of SRAM restricts them to maximum data capacity of 256kb, therefore, SRAM is used in system cache.
DRAM (Dynamic RAM)
DRAM was created to overcome the restriction of SRAM. Even though, DRAM chips provide much slower access time compare to SRAM, it can store several megabytes of data on a single chip. DRAM stores each bit of data in a separate capacitor inside an integrated circuit and need to be refresh periodically. However, with the constant refresh, it can make access even much slower and causes the DRAM chips to draw extra power from the computer. Thereafter, DRAM is used as main memory in the computer because of it high capacity and low cost.
EDO RAM (Extended Data Output RAM)
EDO RAM is the leading RAM in the mid-1900s. When one piece of data is being sent to the processer, another is being retrieved from the RAM module. The usual accessed time for EDO DRAM is 60 ns.
SDRAM (Synchronous DRAM)
SDRAM is around twice as fast as EDO RAM because it is able to run the speed at the speed of the system bus (up to 100-133 MHz). Besides, SDRAM allow new memory access before the proceeding access is accomplished.
RDRAM (Rambus RAM)
The name Rambus originated from a company named Rambus Inc that manufactured it and RDRAM has a data transfer rate of 800MHz. RDRAM can only used in computers with special RDRAM channels and slots.
DDR RAM (Double-data Rate RAM)
DDR RAM is used to replace SDRAM which it can double the rate speed at which standard SDRAM can process. The data transfer rate of DDR RAM is between 100 and 200MHz.
DDR RAM
DDR2 RAM
DDR2 RAM is the newer version of DDR RAM. The data transfer rate is between 200 and 400MHz. the significant features in DDR2 RAM are higher speed, density and require lower power than DDR RAM.
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