The Computer Revolution/Hardware/Virtual Memory
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Virtual memory is a management technique used by operating systems. Virtual memory is only not virtual at all, it uses a portion of the computers hard drive appropriated for some functions of RAM if more memory is required to run things than the virtual memory can provide without slowing down. Program and data placed in RAM is divided into fixed-length pages, it depends on the operating system used. Virtual memory allows to use more memory than is physically available on the computer.
Virtual memory is a common part of most operating systems found in desktop computers. Because the ram on the ordinary computer isn’t enough to run all of the programs that most users need to at the same time, virtual memory is required. Without virtual memory you would not be able to open a web browser and a word processor program at the same time. Virtual memory allows the computer to look at RAM for areas that have not been used recently and copy them onto the hard disk. This frees up enough space in RAM so that the user can load the new program. Since the hard disk space is much cheaper than RAM chips, virtual memory has an economic benefit to it. However, since the read/write speed of a hard drive is much slower than RAM the user may find that there is a performance drop if the computer relies too heavily on the virtual memory. The key for the user is to have enough RAM to handle everything they tend to work on simultaneously so that the only time there seems to be slowness due to virtual memory reliance is when they’re changing tasks only.
An Austrian astronomer named Rudi Albrecht worked at ESO developed a virtual memory system to handle files on tape that were larger than the available memory on his Hewlett Packard 2116 microcomputer (A large computer with one processor and 16 kilobytes of magnetic-core memory). His contributions helped develop our current technology in regards to virtual memory today. http://www.eso.org/public/images/potw1223b Here is a link of Albrecht today in the Data Center at ESO Headquarters in Germany surrounded by a 40 processor core, 138 terabyte storage and 83 gigs of RAM.