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XIP
In computer science, execute in place (XIP) is a method of executing programs directly from long-term storage rather than copying it into RAM. It is an extension of using shared memory to reduce the total amount of memory required. Its general effect is that the program text consumes no writable memory, saving it for dynamic data, and that all instances of the program are run from a single copy. For this to work, several criteria have to be met: * The storage must provide a similar interface to the CPU as regular memory (or an adaptive layer must be present). * This interface must provide sufficiently fast read operations with a random access pattern. * The file system, if one is used, needs to expose appropriate mapping functions. * The program must either be linked to be aware of the address the storage appears at in the system or be position-independent. * The program must not modify data within the loaded image. The storage requirements are usually met by using NOR flash ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AXFS
AXFS (Advanced XIP Filesystem) is a compressed read-only file system for Linux, initially developed at Intel, and now maintained at Numonyx. It was designed to use execute in place (XIP) alongside compression aiming to reduce boot and program load times, while retaining a small memory footprint for embedded devices. This is achieved by mixing compressed and uncompressed pages in the same executable file. AXFS is free software (licensed under the GPL). Cramfs is another read-only compressed file system that supports XIP (with patches); however, it uses a strategy of decompressing entire files, whereas AXFS supports XIP with page granularity.Justin Treon, (2008-05-09) ', LinuxDevices.com, "There are two XIP-enabled Linux filing systems that can be used for a Balanced XIP implementation: Linear XIP CRAMFS and AXFS. The Linear XIP CRAMFS decompresses files on a file-by-file basis, whereas AXFS decompresses files on a page-by-page basis offering more optimal Flash usage." See also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flash Memory
Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both use the same cell design, consisting of floating gate MOSFETs. They differ at the circuit level depending on whether the state of the bit line or word lines is pulled high or low: in NAND flash, the relationship between the bit line and the word lines resembles a NAND gate; in NOR flash, it resembles a NOR gate. Flash memory, a type of floating-gate memory, was invented at Toshiba in 1980 and is based on EEPROM technology. Toshiba began marketing flash memory in 1987. EPROMs had to be erased completely before they could be rewritten. NAND flash memory, however, may be erased, written, and read in blocks (or pages), which generally are much smaller than the entire device. NOR flash memory allows a single machine word to be written to an era ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparison Of File Systems
The following tables compare general and technical information for a number of file systems. General information Limits Metadata Features File capabilities Block capabilities Note that in addition to the below table, block capabilities can be implemented below the file system layer in Linux ( LVM, integritysetup, cryptsetup) or Windows (Volume Shadow Copy Service, SECURITY), etc. Resize capabilities "online" and "offline" are synonymous with "mounted" and "not mounted". Allocation and layout policies OS support See also * List of file systems * Comparison of file archivers * List of archive formats * Comparison of archive formats Notes References External links A speed comparison of filesystems on Linux 2.4.5(archived) Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch{{Webarchive, url=https://web.archive.org/web/20180304191727/https://debian-administration.org/article/388/Filesystems_ext3_reiser_xfs_jfs_comparison ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shared Memory (interprocess Communication)
In computer science, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Shared memory is an efficient means of passing data between programs. Depending on context, programs may run on a single processor or on multiple separate processors. Using memory for communication inside a single program, e.g. among its multiple threads, is also referred to as shared memory. In hardware In computer hardware, ''shared memory'' refers to a (typically large) block of random access memory (RAM) that can be accessed by several different central processing units (CPUs) in a multiprocessor computer system. Shared memory systems may use: * uniform memory access (UMA): all the processors share the physical memory uniformly; * non-uniform memory access (NUMA): memory access time depends on the memory location relative to a processor; * cache-only memory architecture (COMA): the local memor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical disciplines (including the design and implementation of Computer architecture, hardware and Computer programming, software). Computer science is generally considered an area of research, academic research and distinct from computer programming. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and for preventing Vulnerability (computing), security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Progr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Page Table
A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the program executed by the accessing process, while physical addresses are used by the hardware, or more specifically, by the random-access memory (RAM) subsystem. The page table is a key component of virtual address translation that is necessary to access data in memory. Role of the page table In operating systems that use virtual memory, every process is given the impression that it is working with large, contiguous sections of memory. Physically, the memory of each process may be dispersed across different areas of physical memory, or may have been moved ( paged out) to secondary storage, typically to a hard disk drive (HDD) or solid-state drive (SSD). When a process requests access to data in its memory, it is the responsibility of the operating system to map the virtual addres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ottawa Linux Symposium
The Linux Symposium was a Linux and Open Source conference held annually in Canada from 1999 to 2014. The conference was initially named Ottawa Linux Symposium and was held only in Ottawa, but was renamed after being held in other cities in Canada. Even after the name change, however, it was still referred to as OLS. The conference featured 100+ paper presentations, tutorials, birds of a feather sessions and mini summits on a wide range of topics. There were 650 attendees from 20+ countries in 2008. History The 2009 Symposium was held in Montréal, Quebec. The 2011 and 2012 Symposium were both held in Ottawa. In 2014, OLS organizers put together an unsuccessful campaign on Indiegogo to raise funds in order to pay off debts from previous events. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firmware
In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide hardware abstraction services to higher-level software such as operating systems. For less complex devices, firmware may act as the device's complete operating system, performing all control, monitoring and data manipulation functions. Typical examples of devices containing firmware are embedded systems (running embedded software), home and personal-use appliances, computers, and computer peripherals. Firmware is held in non-volatile memory devices such as ROM, EPROM, EEPROM, and flash memory. Updating firmware requires ROM integrated circuits to be physically replaced, or EPROM or flash memory to be reprogrammed through a special procedure. Some firmware memory devices are permanently installed and cannot be changed after manufacture. C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NetBSD
NetBSD is a free and open-source Unix operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems. The NetBSD project focuses on code clarity, careful design, and portability across many computer architectures. Its source code is publicly available and permissively licensed. History NetBSD was originally derived from the 4.3BSD-Reno release of the Berkeley Software Distribution from the Computer Systems Research Group of the University of California, Berkeley, via their Net/2 source code release and the 386BSD project. The NetBSD project began as a result of frustration within the 386BSD developer community with the pace and direction of the operating system's development. The four founders of the NetBSD project, Chris Demetriou, Theo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
User-space
A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour. Kernel space is strictly reserved for running a privileged operating system kernel, kernel extensions, and most device drivers. In contrast, user space is the memory area where application software and some drivers execute. Overview The term user space (or userland) refers to all code that runs outside the operating system's kernel. User space usually refers to the various programs and libraries that the operating system uses to interact with the kernel: software that performs input/output, manipulates file system objects, application software, etc. Each user space process normally runs in its own virtual memory space, and, unless explicitly allowed, cannot access the memory of other processes. This is the basis for memory protection in tod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOS Technology 6532
The 6532 RAM-I/O-Timer (RIOT) was an integrated circuit made by MOS Technology, as well as second sources such as Rockwell. It incorporated 128 bytes of static RAM, two bidirectional 8-bit digital input/output ports, and a Programmable interval timer. This high degree of integration made it quite popular in the late 1970s and early 1980s, as it could take the place of several different integrated circuits (ICs). Perhaps its best-known application was the Atari 2600 video game console. The chip was also famously deployed in Gottlieb pinball machines, such as ''Haunted House'' and '' Black Hole'', the Atari 810 and 1050 disk drives, as well as Commodore's 8050, 8250 & 8250LP PET disk drives. The Atari 850 Interface, which gave Atari 400 and 800 computers an RS-232 interface, used two 6532 chips. 6532 ICs were available in 1 MHz and 2 MHz versions. The form factor was a JEDEC The JEDEC Solid State Technology Association is an independent semiconductor engineering tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
