TEL VME-U10B 381-641697-5 模拟量输出模块

TEL VME-U10B 381-641697-5   模拟量输出模块

计算机是第一台具有真正虚拟内存的计算机。第一个真正的虚拟内存系统是在曼彻斯特大学创建一级存储系统作为的一部分阿特拉斯计算机。它使用了一个分页将程序员可用的虚拟地址映射到由16，384个主内存字组成的真实内存的机制磁心存储器再加上98304字的二次计算机的磁鼓记忆装置。将虚拟内存添加到Atlas中还消除了一个迫在眉睫的编程问题:规划和调度主内存和辅助内存之间的数据传输，并针对主内存大小的每次变化重新编译程序。第一个Atlas于1962年投入使用，但寻呼的工作原型在1959年就已经开发出来了。1961年巴勒斯公司独立发布了第一台带有虚拟内存的商用计算机B5000，与分割而不是寻呼。

访问存储器中一个特定位置所需的时间。相关的测量单位通常是十亿分之一秒对于主存储，毫秒用于二级存储，以及第二用于三级存储。将读取等待时间和写入等待时间分开(特别是对于非易失性存储器)以及在顺序存取存储的情况下，最小、最大和平均等待时间是有意义的。从存储器中读取信息或向存储器中写入信息的速率。在计算机数据存储中，吞吐量通常用每秒兆字节(MB/s)来表示比特率也可以使用。与延迟一样，可能需要区分读取速率和写入速率。此外，顺序访问介质(而不是随机访问)通常会产生最大的吞吐量。存储信息的紧凑性。它是介质的存储容量除以长度、面积或体积的单位(如每平方英寸1.2兆字节)。基于存储在那里的(部分)内容来选择每个可单独访问的信息单元。内容寻址存储可以使用软件(计算机程序)或五金器具(计算机设备)，硬件速度更快，但价格更高。硬件内容可寻址存储器通常用于计算机的CPU缓存。

TEL VME-U10B 381-641697-5   模拟量输出模块

Computer is the first computer with real virtual memory. The first real virtual memory system was created in Manchester University as a part of Atlas computer. It uses a paging mechanism to map the virtual address available to the programmer to the real memory consisting of 16,384 main memory words, the core memory plus the drum memory device of the secondary computer with 98,304 words. Adding virtual memory to Atlas also eliminates an urgent programming problem: planning and scheduling data transmission between main memory and auxiliary memory, and recompiling the program for each change of main memory size. The first Atlas was put into use in 1962, but the working prototype of paging was developed in 1959. In 1961, Burroughs Company independently released the first commercial computer B5000 with virtual memory, which was divided instead of paging.

The time required to access a specific location in memory. The relevant units of measurement are usually billionths of a second for primary storage, milliseconds for secondary storage, and second for tertiary storage. It makes sense to separate the read latency from the write latency (especially for nonvolatile memory) and in the case of sequential access storage, the minimum, maximum and average latency. The rate at which information is read from or written to memory. In computer data storage, throughput is usually expressed in megabytes per second (MB/s), and bit rate can also be used. As with latency, it may be necessary to distinguish between read rate and write rate. In addition, sequential access to media (rather than random access) usually produces the maximum throughput. The compactness of stored information. It is the storage capacity of a medium divided by the length, area or volume (for example, 1.2 megabytes per square inch). Each individually accessible information unit is selected based on the (partial) content stored there. Content addressable storage can use software (computer program) or hardware (computer equipment), which is faster but more expensive. Hardware content addressable memory is usually used for CPU cache of computers.