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Computer Storage A Medium Used To Store A Discontinuous Physical Quantity In Computer Memory
Sep 14, 2017

A medium used to store a discontinuous physical quantity in computer memory. Computer storage media are mainly semiconductor, magnetic core, drum, tape, laser disc and so on. Semiconductor memory for the computer's semiconductor storage components are mainly Mos and bipolar type two. Mos component integration is high, the process is simple but slower. Bipolar components of the complex process, power consumption, low integration but fast. NMos and CMos after the advent of the Mos memory in the semiconductor memory began to dominate. NMos speed, such as Intel's 1K bit static random access memory access time is 45ns. While the CMos power consumption, 4K bit CMos static memory access time is 300ns. The above-mentioned semiconductor memories are random access memory (RAM), that is, in the course of work can be randomly read and write new content. The semiconductor read-only memory (ROM) in the course of work can be randomly read but can not write, it is used to store the program has been cured and data. ROM is divided into non-rewritable fuse-type read-only memory ─ ─ PROM and rewritable read-only memory EPROM two.

Core memory due to low cost, high reliability, and more than 20 years of practical experience. The core memory was widely used as the main memory before the mid-1970s. Its storage capacity of up to 10 or more, the fastest access time of 300ns. International typical core memory capacity of 4MS ~ 8MB, access cycle of 1.0 ~ 1.5μs. After the semiconductor storage is rapidly evolving to replace the core memory as the location of the main memory, the core memory can still be used as a large-capacity expansion memory. Figure 1 for the early production of IBM 64-bit / chip semiconductor chip chip placed in the same period on the production of the core memory board, you can see a chip equivalent to about 6 core area, that is, surface density increased by 10 times. The development of contemporary semiconductor integrated circuits has raised this scale several times in magnitude.

A external memory of magnetic recording. Because of its fast access to information, stable and reliable, although its smaller capacity, is gradually being replaced by disk storage, but still used as real-time process control computer and medium and large computer external memory. In order to meet the needs of small and micro-computer, the emergence of ultra-small drum, its small size, light weight, high reliability, easy to use.

A external memory of magnetic recording. It has the advantage of both drum and tape memory, that is, its storage capacity is larger than the drum capacity, and access speed is faster than the tape memory, but also offline storage, so in a variety of computer systems are widely used as a large disk Capacity of the external memory. Disk is generally divided into hard disk and floppy disk storage two categories. There are many varieties of hard disk memory. From the structure, the sub-exchangeable and fixed two. Replaceable disk discs are removable and fixed disk discs are fixed. Both interchangeable and fixed disks have multiple combinations and monolithic structures, and can be divided into fixed head type and movable head type. Fixed head type disk capacity is small, recording density is low access speed, but the cost is high. The active head type disc has a high recording density (up to 1000 to 6250 bits per inch) and thus a large capacity, but the access speed is relatively low relative to the fixed head disk. The current disk storage capacity of up to hundreds of megabytes, bit density of 6,225 per inch, the road density of 475 per inch. Among them, multi-chip removable disk memory can be used in online information retrieval system and database management system because of its large dismantling capacity, large capacity and high speed, which can store large-capacity intelligence data. Activity head fixed disk in recent years in the technology has been greatly improved, as a sealed combination of fixed disk disk storage, known as the Winchester disk. This disk is small, high reliability, large capacity, high recording density, on behalf of the current disk memory development direction.

Soft disk memory is developed in recent years, a new type of disk, the capacity of about 1-3MB. It is characterized by cheap, versatile, easy to use and portable, to meet the micro-computer system to auxiliary storage small, reliable and inexpensive requirements. Soft disk discs are 8 inches, 5 inches, 3.5 inches and so on. In addition to suitable for microcomputer external memory, floppy disk storage can also be used with the input keyboard from the key to the floppy disk input device instead of the traditional use of perforated paper and perforated card. Information can be stored offline on floppy disks and loaded into floppy disks for use in computers. The floppy disk memory storage medium is a floppy disk, its structure and shape shown in Figure 3.

Tape memory is still used for large capacity auxiliary memory because of its large capacity, low price and long-term storage. International tape machine commonly used semi-inch tape, track 7 or 9 tracks, recording density of 800,1600,3200 per inch, up to 6250, with a speed of 75 to 250 inches / second. Small tape machine for small machine, also known as cassette tape drive, the bandwidth is generally 0.15 inches, track for the 2, with a speed of 75 inches / second, recording density of 800 / inch. Large tape cartridge bandwidth of 0.25 inches, track for the four, recording density of 1600 / inch. Foreign tape in the form of a large number of databases issued, so through the tape drive can be directly into the computer intelligence information processing and retrieval. In order to meet the needs of large-scale systems, but also the development of massive tape memory, such as IBM3850 massive tape memory, storage capacity up to 472000MB.

CD-ROM memory is the use of laser read and write information memory, the main advantage is high density, large capacity, a 12-inch diameter disc can store 2.5GB of information, bit storage cost is low. CD access time than disk access time is long, generally 100 ~ 500ms, another drawback is that the recorded information can not erase rewrite.