Virtual memory

The question as to whether and to what extent and in what area optical mass storage would replace magnetic systems (disk, tape) was controversially being discussed in the 1980s. In spite of all predictions of an imminent substitution, as of late 1994 magnetic hard disks stiU are the system of choice for computer-dedicated mass storage due to their speed (access time, transfer rate), physical size, and energy consumption this is especially tme when memory-intensive appHcations are mn which use the hard disk as virtual memory. 

Everything in QED is stored in "triples like in the LEAP language. (28) Each triple consists of an index, an attribute, and a value. QED maintains pointer lists to entries that have the same index, attribute, or value so that it can quickly retrieve relations given any combination of I, A, or V. The triples are stored in QED s software implemented virtual memory that is mapped to disk. The internal form of the ALPHA-TO-SC rule is shown in Table IV. 

The memory organization of DSPs are also different from ordinary processors because (1) Memory is typical static RAM and virtual memory support is totally absent (2) Several machines separate data and instruction streams (Harvard Architecture) (at the cost of extra pins). Additionally, modular arithmetic address modes have been added to most processors. This mode finds particular utility in filter coefficient pointers, ring buffer pointers and, with bit reversed addressing, FFTs. One further difference is the use of loop buffers for filtering. Although often called instruction caches by the chip manufacturers, they are typically very small (for example, the AT T DSP-16 has 16 instructions) and furthermore, the buffer is not directly interposed between memory and the processor. 

A large program space requiring virtual memory. 

Any machine with virtual memory suffers performance degradation when page swaps are too frequent. Some pipelined machines like the TI-ASC (3) or the CDC Star-100 (4) have rather long setup times for their arithmetic pipes. Multiprocessor machines like the Illiac IV (5) are next to useless if the programmer pays no attention to the architecture. These features all directly impact the user they have not been effectively hidden by software at any level. Improvement of this situation could result if compilers took on the burden of optimizing code so as to promote efficient hardware utilization. 

Virtual memory (allows a microcomputer to act as though it were a much larger machine)... 

NUMA is one of the fundamental concepts needed to understand the design of a parallel software application. Every modern computer has several levels of memory, and parallel computers tend to have more levels than uniprocessors. Typical memory levels in a parallel computer include the processor registers, local cache memory, local main memory, and remote memory. If the parallel computer supports virtual memory, local and remote disk are added to this hierarchy. These levels vary in size, speed, and method of access. In this chapter, we will lump all these differences under the general term nonuniform memory access (NUMA). Note that this is a broader use of the term than is often found in computer science literature, where NUMA often refers only to differences in the speed with which given memory items can be accessed using the same method. In our use, memory access is often synonymous with data transfer. ... 

Complex numbers Composite family Composite materials Composting Compound, chemical Compton effect Compulsion Computer, analog Computer, digital Computer languages Computer memory, physical and virtual memory Computer software Computer virus... 

Windows 3.0 featured a far more flexible memory model, allowing it to access more memory than the 640KB limit normally imposed by DOS. It also featured the addition of the File Manager and Program Manager, allowed for network support, and could operate in 386 Enhanced mode. 386 Enhanced mode used parts of the hard drive as virtual memory and was therefore able to use disk... 

System, configuration, and user interface files lO.SYS BOOT.INI WIN.COM MSDOS.SYS AUTOEXEC.BAT CONFIG.SYS Command line prompt VIemory management Conventional Extended/upper memory High memory Virtual memory... 

As shown Figure 13.33, the default behavior for virtual memory is that Windows 9x simply handles it for you. This is a good thing, and unless you have a particular need to modify the file, you are best served by letting the computer handle it. If a particular application does require extensive virtual memory, you can modify it easily, though. To find the Virtual Memory button, choose Start > Settings > Control Panel. Double-click the System icon and select the Performance tab. The Virtual Memory button is along the bottom of the window. 

Let Wrdows manage my virtual memory settings. (Recommended C Let me specif my own virtual memory settings. 

Once the machine is up and running, getting it to run better, or to support certain applications, may require additional configuration. Tools such as the Registry Editor and Device Manager facilitate this, as do configuration options such as the Virtual Memory settings. 

Although it is hidden away in the backwaters of Windows 2000 s system configuration settings, the Performance button holds some of the most important settings you may need to configure on a 2000 Professional system. Among the settings in the Performance window are the size of your virtual memory and the maximum... 

The initial Performance window has two options application response and virtual memory. Application response is normally not something you will need to modify. It is set by default to optimize the system for foreground applications, making the system most responsive to the user who is running programs. This is generally best, but it does mean that any applications (databases, network services, etc.) that are run by the system are given less time by the system. 

The virtual memory settings (see Figure 14.14) tell you how much hard drive space is allocated to the system as a swap file. For a review of what virtual memory is, return to Part II, Chapter 13, Windows 95/98. Windows 2000 recommends a particular virtual memory level, but you can add to or subtract from this as you need. Often, certain applications (SQL Server for instance) will need to have Windows 2000 Professional s virtual memory limit raised in order to work properly. Graphics and CAD applications also require raising the virtual memory level, but if this is the case, the setup instructions for the application will generally tell you what modifications need to be made. 

A. You can change the size of virtual memory and the maximum size of the... 

You can change the size of virtual memory and the maximum size of the Registry by accessing the Control Panel and clicking the Virtual Memory icon. Registry size may also be changed within that option. 

Virtual memory and Registry size are changed during the setup process. From that point on, they automatically change based upon the user profile. D. Virtual memory and Registry size should not be modified. 

B. Open the Control Panel, click the System Panel button, select the Advanced tab, click the Performance button, and then increase the size of your virtual memory. 

A. There are three subheadings under the Advanced tab Performance, Environment Variables, and Startup and Recovery. The Performance button allows you to change the size of your virtual memory and Registry. 

B. The virtual memory settings tell the user how much hard drive space is allocated to the system as a swap file. With minimum RAM on the system illustrated in this question, this setting may need to be modified. 

ALEX and Smalltalk/V create a virtual memory structure with an efficient paging facility to minimize the memory limitations of the PC delivery platform. 

In this early study SCF and SCF-CI computations were carried out by the technique described above on a DEC PDP-11/55 with the hard drive providing virtual memory. For these computations, a truncated set of basis orbitals was used. The truncation criterion utilized those orbitals that were part of the n-system and those that were involved in bond formation or loss of a bond. 

The operating system (e.g., VMS [Virtual Memory System], Windows NT, etc.) provides the platform for the product. Where the operating system utilized is an "established, commercially available operating system. . . ", the funaion-ality of the operating system is considered validated as part of the application software. 

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