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| | [No title] |
 | | Therefore the total amount of virtual memory is the number of segments (16,384) times the number of bytes (64K) per segment, or 1 GB. | | | B) The advantage of page-based virtual memory over segments only based virtual memory is that the swapping is much more efficient since the data is broken into 4K chunks. | | | A) Three major advances that the 80386 has over the 80286 are a 32-bit versus a 16-bit Arithmetic Logic Unit, an allowable segment size of up to 4GB instead of 64K, and the addition of a "virtual 8086" mode which allows the 80386 to switch between protected and real-mode tasks. |
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http://coscorrosa.com/school/sophomore/cs201/201-8.html
(722 words)
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| | Windows NT: Lesson 7 - The Virtual Memory Manager |
| | When the computer's physical memory is in high demand, the virtual memory manager is responsible for swapping (copying) code and data to disk for temporary storage. | | | Effectively, the virtual memory available on a computer is equal to its physical memory plus whatever hard disk space the virtual memory manager uses to temporarily store swapped code and data. | | | In this case, the three blocks of free memory were consolidated into one larger block by moving system memory upward and application 1 downward in physical memory. |
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http://www.microsoft.com/technet/archive/winntas/training/ntarchitectoview/ntarc_7.mspx
(2957 words)
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| | CS554A Syllabus: Memory Management Tutorial. |
| | However, the existence of those page tables makes the physical memory location of a program's memory pages transparent to the program itself, so that the programmer and most higher level components of the Operating System think they're operating in a contiguous piece of memory. | | | Because the machine's memory is finite, there will always be pages that don't fit in physical memory: these pages will be paged out to mass storage by the OS, and swapped back in when required. | | | A virtual address page may be mapped to physical memory, or it may be mapped to memory that's swapped out to mass storage. |
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http://www.rivier.edu/faculty/amoreira/web/cs554a/Tut3
(1676 words)
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| | [No title] |
| | The amount of memory allocated for the interrupt stack is determined by the interrupt_stack_size field in the CPU Configuration Table. | | | RTEMS assumes that the memory regions in which its code, data, and the RTEMS Workspace reside are configured as little endian. | | | Although the models do vary in significant ways, the high level of compatibility makes it possible to share the bulk of the CPU dependent executive code across the entire family. |
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http://www.rtems.com/onlinedocs/rtems-doc-20030417/info/i960.info-1
(5160 words)
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| |
| | Flat (disambiguation) - Wikipedia, the free encyclopedia |
| | Similarly, a flat file can refer to a flat file database or to a simple type of file system for computers. | | | In computer programming, a flat memory model is an approach to organizing memory address space. | | | In New Zealand, flats refer to houses or other accommodation where groups of people, often University students, live together. |
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http://en.wikipedia.org/wiki/Flat_(disambiguation)
(329 words)
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| | Guide: About the 80386 architecture |
| | Opcodes that operate on memory operands must be modified to indicate the size of the memory operands. | | | That is the lower byte of a word is at a lower memory location than the higher byte of a word. | | | Also the low byte, or low word, is at a lower memory location than the high byte, and high word. |
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http://www.delorie.com/djgpp/doc/ug/asm/about-386.html
(3744 words)
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| | Overview of the OS/2 Operating System |
| | This is in contrast to the segmented memory model implemented by the 80286 processor. | | | Memory objects or parts of memory objects, which are not reuired by the currently executing process, may be temporarily migrated out to secondary storage(disk). | | | Since memory is managed by the operating system on a page-by-page basis, even the allocation of a 1 byte memory object will actually reserve a full page(4KB) in memory. |
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http://www.cs.wayne.edu/~tom/guide/os2.html
(17176 words)
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| | 6.8 NUMA and Peripheral Devices |
| | Unlike caches and the virtual memory subsystem that operate in a transparent fashion, programs that write to NUMA devices must be aware of this and minimize the accesses whenever possible (e.g., by using an off-screen bitmap to hold temporary results). | | | Segments are an especially powerful memory management system when a program needs to manipulate different variable sized objects and the program cannot determine the size of the objects before run time. | | | However, if you are aware of the effects of the memory hierarchy on program performance, you can write faster programs by organizing your data and code so that it conforms to the expectations of the caching and virtual memory subsystems in the memory hierarchy. |
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http://webster.cs.ucr.edu/AoA/Windows/HTML/MemoryArchitecturea4.html
(5625 words)
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| | Optimizing Memory and Processing |
| | With a segmented memory model, memory is broken into a number of 64K chunks called “segments.&; These segments create artificial boundaries that developers are forced to code around, an often difficult and tedious task. | | | This limitation of the segmented memory model is the cause of many of the inherent limitations and problems with MS-DOS and Windows 3.x’s designs, including the 64K resource heap limit that is imposed on the User, GDI, and Kernel heaps in Windows 3.x. | | | Although paging is a neat way of getting more memory than is physically installed on the computer, it can also become a significant performance bottleneck because hard drive access (measured in milliseconds, or thousandths of a second) is exponentially slower than physical RAM access (measured in nanoseconds, or billionths of a second). |
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http://www.windowsitlibrary.com/Content/435/05/2.html
(2202 words)
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| | Virtual memory allocation in Windows 95 |
| | Virtual memory is managed using a swap file containing the current complete memory contents across all processes that are available to execute. | | | Windows 95 uses a flat memory model and a virtual memory paging algorithm. | | | You will be prompted to inform you that you will need to restart your computer for the changes to take effect. |
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http://www.lansa.com/support/tips/e0008.htm
(240 words)
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| | Some fundamental OS/2 concepts - Part 2 |
| | When this code has to be bumped out of main memory to make room for something else, the memory image doesn't need to be saved in the swap file; it can be re-read, the next time it's swapped in, from the original source file. | | | In a typical operating system, the segment tables are maintained by that part of the software that looks after memory allocation, and the page tables are the concern of the software that does disk swapping. | | | With modern processors, we also find that the main memory is itself a bottleneck, in that it can't deal with data as fast as the processor can produce or consume the data. |
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http://www.os2ss.com/Information/Fundamentals/conc2.html
(5391 words)
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| | The memory model |
| | There is memory hierarchy of registers to cache to disk. |
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http://www.cs.washington.edu/homes/mausam/cachepq/tsld002.htm
(10 words)
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| | [No title] |
| | Watcom has a split memory model, with the first megabyte of physical memory mapped to the first megabyte of its logical address space and the data segment and the rest of memory mapped starting at 0x400000. | | | There are three calls that are relevant to conventional memory, 100h/101h/102h, which are for allocating, freeing, and resizing buffers of conventional memory. | | | Unlike real-mode, you cannot simply load this segment a segment register and access the memory (if you want to do it that way, you can access the memory using the selector and 48-bit far pointers). |
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http://homepages.cae.wisc.edu/~brodskye/tomes/watcom.txt
(560 words)
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| | Stack pointer etc |
| | There is nothing in the x86 that prevents the classical virtual memory model from being used, ie, program at 0, stack at 0 (which is the wrapped top of memory), and all memory unregulated and virtual. | | | This is because segments don't matter in virtual memory, the memory access is according to the page tables. | | | Heaps don't need to worry about the guard page problem, because each allocation is done specifically by code, and the "jumpover" check can be done at that time. |
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http://www.codecomments.com/message169077.html
(1077 words)
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| | ERCB: DDJ Programmer's Bookshelf December 1992 |
| | As Stone shows, paged virtual memory depends on the fact that all programs have reasonably sized working sets or "footprints;" that is, that all programs can run for a while with only discrete, page-sized bits of themselves in memory at any given time. | | | The reason for most programmers to study virtual memory, then, is so they can understand its performance implications for their software. | | | Obviously, the presence of virtual memory is no more relevant to your average programmer than is, say, the presence of an instruction prefetch queue on the processor. |
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http://www.ercb.com/ddj/1992/ddj.9212.html
(1414 words)
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| | Cogsys: Data Segments |
| | The data segment is a segment of memory where some of this function's data, including certain constants, local array structures and many other variables specific to the function, resides. | | | The "what" question is easy: as far as the extension writer is concerned, the data segment register should either have it's original value (that is, the value it had when the function was entered), or it should be set to the data segment of the block of memory where the extension was loaded. | | | The value of the data segment register is used whenver the function needs a value from its data segment. |
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http://condor.depaul.edu/~dallbrit/extra/cogsys-html/cogref_89.html
(1272 words)
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| | [No title] |
| | This memory model defaults to near (two-byte) addresses for code and data, which makes the program run faster and use less memory. | | | Choose the smallest memory model available that can contain your data and code, since near references operate more efficiently than far references. | | | Far Code Segments XE "Segments:code:far" \z "SEGMNW.DOC-1169"XE "Memory models:far code segments" \z "SEGMNW.DOC-1170" When you need more than 64K of code, use the medium, large, or huge memory model to create far segments. |
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http://www.mathcs.sjsu.edu/faculty/kennedy/cs140/prguide/chap_02.doc
(7170 words)
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| | EETimes.com - Embedding security into servers |
| | Similar protection word mechanisms are sometimes used by debuggers and memory managers in any kind of memory model, but it's possible to use the bits for so much more. | | | Systems such as Linux and Windows effectively isolate the memory for a process, and a typical RTOS' flat memory model would seem to increase the likelihood of a buffer overrun. | | | Many systems feature their own memory manager, whereby processes allocate and deallocate fixed-size blocks of memory. |
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http://www.eetimes.com/in_focus/communications/OEG20021014S0063
(1745 words)
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| | Linking C & ASM |
| | Note: in the 32-bit FLAT memory model, all addresses in memory are 4 bytes long and it is not necessary to use the SEGMENT:OFFSET format to refer to a memory location. | | | Memory window--- you will need to set a memory address to look at. | | | This can be done by copying an address from a register and pasting it into the 0x00000000 address field an replacing the string of 0's with the numeric value of the address being used. |
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http://www2.hawaii.edu/~walbritt/ics312/hllInterface/notesSally.htm
(1407 words)
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| | Runtime Environment |
| | The memory model chosen determines whether near or far addressing is used to access various objects like procedures, variables, parameters, and pointers. | | | For purposes of defining the memory models, the data accessed by a Stony Brook program is divided into five data classes: | | | A group is a logical structure used by the linker to represent a set of data that is limited to 64K bytes. |
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http://www.modula2.org/sb/websitearchive/env/index590.htm
(1824 words)
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| | Format of Pointers in Unix |
| | Hello, On a x86 machine, what is the format of a pointer in C? I know for a fact that the x86 p-mode uses a /selector:offset/ notation where the selector is defined in either the GDT or LDT. | | | Furthermore, keep in mind that all modern OSes use _virtual_ memory, so you'll probably find that two different pointers in two different programs can hold the same value, but that's normal, since they are virtual addresses. | | | All unixes I've seen use a flat memory model for user space applications. |
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http://www.codecomments.com/message197115.html
(1999 words)
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| | [No title] |
| | Whenever memory is accessed, be it instruction fetch, data read or data write, the attributes of the used segment are checked against the instruction. | | | The error conditions are many, and the reader is referred to Intel's 80386 Programmer's Reference Manual for details. | | | All Intel 80386 (and higher) microprocessors share the same strategy for memory access. |
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http://www.ddci.com/art_10040.php
(663 words)
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| | Memory Model Flat Memory Model |
| | Each address is represented by a 32-bit value and memory is addressable. | | | By not requiring that logical addresses map directly to physical addresses, the memory space of an RTEMS space can be separated from that of a ROM monitor. | | | RTEMS treats the space registers as system resources shared by all tasks and does not modify or context switch them. |
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http://www.rtems.com/onlinedocs/releases/4.0.0/doc/support/c_hppa1_1/a00014.html
(297 words)
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| | EETimes.com - RTOSes shield from net-centric bugs |
| | A critical but largely unaddressed problem for net-centric computing infrastructures is viruses, whether inserted maliciously or the result of bad code-that is, bugs. | | | If the task or tasks in a particular address space are badly written and exceed the quota established by the system designer, then they cannot execute. | | | The number of address spaces is limited only by either the processor capacity or the available memory. |
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http://www.eetimes.com/story/OEG20010406S0049
(1497 words)
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| | Porting MicroC/OS-II to the X86 (PM) |
| | DEBUG loads the file in memory at offset 0100h (the segment address is irrelevant) and copies 512 bytes from offset 100h (where the file is) onto drive A, on track 0, for 1 sector (512 bytes). | | | Loads the first 64k of the floppy disk (the first file in fact) at the physical address 1000h (we will see why this address is important later). | | | Since all tasks are given full privileges (CPL 0) and share the same address space (e.g. |
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http://www.exposecorp.com/embedded/portx86p-2.htm
(1498 words)
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| | [No title] |
| | 2.4.3 Memory (pg 55) Basic types of memory are ROM (Read-Only Memory), which can't be altered, EPROM (Erasable Programmable Read-Only Memory), can be erased, reprogrammed, Dynamic RAM (Random Access Memory), inexpensive, must be refreshed constantly, Static RAM, expensive, high-speed cache memory which doesn't need refreshing. | | | Virtual memory allows total running program to exceed physical memory (4 GB). | | | 2.2.4.3 CISC and RISC (pg 46) Early Intel processors were based on a Complex Instruction Set (CISC) model. |
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http://grail.cba.csuohio.edu/~jackie/cis335/notes/cis33503.txt
(1159 words)
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| | Out-of-Core Divisible Load Processing |
| | The problem is to partition the load so that the total processing time, including communications and computations, is the shortest possible. | | | In this paper, we analyze processing divisible loads in systems with a memory hierarchy. | | | Divisible loads are computations that can be divided into parts of arbitrary sizes and these parts can be independently processed in a distributed system. |
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http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/trans/td/&toc=comp/trans/td/2003/10/lxtoc.xml&DOI=10.1109/TPDS.2003.1239872
(680 words)
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| | Allocatin 320*200 in TURBOC - GameDev.Net Discussion Forums |
| | You'll need to use far pointers or a huge memory model instead, unfortunately I don't know how to allocate them properly from C (I always just took a memory area without asking or used a DOS interrupt instead). | | | Posted - 1/30/2005 6:05:46 PM There shouldn't be any problem with allocating 64000 bytes as it's less than a segment.. | | | EDIT: also you might need to write your 320*200 as 320*200L as it might be doing 16 bit arithmetic. |
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http://www.gamedev.net/community/forums/topic.asp?topic_id=297733
(899 words)
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| | Hexapedia - 32-bit application |
| | The shift from 16-bit software to 32-bit software on IBM compatible systems became possible with the introduction of the '386 microprocessor. | | | The term 32-bit application came about because DOS and Microsoft Windows were originally written for the Intel 8088 and Intel 80286 microprocessors. | | | Furthermore, programming with segments is more involved than programming in a flat address space, giving rise to some complications in programming languages like "memory models" in C programming language and C plus plus programming language. |
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http://www.hexafind.com/encyclopedia/32-bit_application
(307 words)
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| | Technote103 |
| | EMS memory (Which is provided by EMM386) was available on 808x CPU's through special bank-switching hardware (LIM memory cards), on 386+ CPUs, this is simulated through the paging features of these CPU's in protected mode. | | | This is possible on the 80286, 80386, and some 80486 by using an instruction called 'loadall'. | | | The same goes for the INT15h functions introduced with the IBM PC, but there had been no "security" build in to prevent that two programs access the same memory areas (other than XMS,the functions don't keep track of the allocated memory areas). |
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http://www.freedos.org/freedos/news/technote/103.html
(756 words)
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| | Memory Model Flat Memory Model |
| | For example, on the Force Computers CPU386, the ROM monitor loads application programs into a logical address space where logical address 0x00000000 corresponds to physical address 0x0002000. | | | Each address is represented by a 32-bit value and is byte addressable. | | | The selector number of this segment is provided to RTEMS in the CPU Dependent Information Table. |
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http://www.engr.usask.ca/classes/EP/424/lab/rtemsdocs/i386/i38600016.html
(338 words)
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| | OSNews.com |
| | All things being equal, a larger pointer size requires more memory which requires a faster memory bus to get the same performance, and the memory bus is already slowing things down. | | | As to why we don't have 128bit cpu, well I think we don't need that large of a number represented by 128bits and/or don't need to address such huge memory yet. | | | This tends to bloat every structure that contains pointers, and is the primary reason that 64-bit programs tend to need twice the core memory of the 32-bit equivalent. |
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http://www.osnews.com/comment.php?news_id=9498&offset=30&rows=45
(1471 words)
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| | Memory Model Flat Memory Model |
| | RTEMS does not support any SPARC Memory Management Units, therefore, virtual memory or segmentation systems involving the SPARC are not supported. | | | Each address is represented by a 32-bit value and is byte addressable. | | | Memory accesses which are not properly aligned generate a "memory address not aligned" trap (type number 7). |
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http://www.engr.usask.ca/classes/EP/424/lab/rtemsdocs/sparc/sparc00025.html
(236 words)
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| | The pre-boot sequence initializes the computer and locates the boot sector |
| | The minifile system that is used depends on whether Windows NT will be loaded from NTFS or FAT. | | | The boot sequence prepares the computer for the Windows NT load phases to begin. | | | The boot sequence for an Intel-based computer uses the NTLDR, BOOT.INI, BOOTSECT.DOS, NTDETECT.COM and NTOSKRNL.EXE files and consists of the following steps: |
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http://home.clara.net/gwood/nt4/Information/Server/initialisation/intel-boot.htm
(276 words)
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| |
| | CauseWay for Watcom C/C++ & Assembly Language: Manual Page 30 |
| | Creating a standard DOS EXE-format file only works for programs which do not exceed the DOS memory limit when fully loaded into memory. | | | Medium to large-sized programs which require a DOS extender or overlays probably will not work when linked using the /ex option. | | | This option instructs WL32 to create a standard real mode DOS EXE- format file, similar to those created by non-DOS extended linkers such as TLink or Microsoft Link. |
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http://www.devoresoftware.com/cwwman/page_30.htm
(301 words)
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| | [No title] |
| | two-level page tables; Figure in page 283 of the dinasour book; Windows 95: three memory models:. | | | ) ------------------------------------------------------------------------------ Sharing in VM: Example: - Solaris 2.5 Memory Regions: ------------------------------------------------------------------------------ Example: - Windows 95 i386: Segmentation with Paging:. | | | segment + offset used to generate the 20-bit address; ============================================================================== Multiprogramming and Paging: (section 9.6) (minimum number of page frames;) - global replacement versus local replacement; In local replacement: - equal allocation; - proportional allocation; - thrashing: one process thrashing; multiple process thrashing; - working set model; - page fault frequency; ============================================================================== |
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http://www.cs.wisc.edu/~cao/cs537/lecture18-discussion.txt
(372 words)
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| | When you should use segmentation |
| | It's not a good idea for C projects, since C wasn't constructed with segmentation in mind. | | | In a assembler project, this isn't very common, so it doesn't affect performance too much. | | | Returns to invalid code is caught at return instruction (easier to debug) |
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http://www.rdos.net/misc/segment.htm
(136 words)
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| | Programming with the Intel architecture in the flat memory model |
| | How to initialize the Intel386™ and Intel486™ processors to run in protected mode using the flat memory model. | | | Programming with the Intel architecture in the flat memory model | | | Tools available for programming in the flat memory model. |
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http://www.intel.com/design/intarch/PAPERS/ESC_IA_P.HTM
(58 words)
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| | Utilized Protected Mode Features |
| | With this hurdle cleared, it will also be possible to allocate threads in different protected memory segments, allowing for the protection of one thread from another's errors. | | | When in real-mode (for disk reads, console input and output) the results of I/O must be transfered to a real-mode segment. | | | We are restricted, however, to an amount of memory that corresponds to a single real-mode segment. |
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http://www.cs.virginia.edu/~bah6f/nachos486/paper/node15.html
(130 words)
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| | [No title] |
| | ;* ;* ======================================================================== ;* ;* Language: NetWide Assembler (NASM) ;* Environment: Any Intel IA32 Environment ;* ;* Description: Macros to provide memory model independant assembly language ;* module for C programming. | | | This evaluates to nothing in the flat memory ; model, but is saves and restores DS in the large memory model. | | | This does nothing for 32-bit code, but for 16-bit code ; will set up a far model code segment as well for later use. |
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http://unununium.org/darcs/scitech-snap/include/scitech.mac
(1110 words)
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| | [No title] |
| | BPERL1S.ZIP 32-bit Perl 4.0pl36 w/VM & Win 3.1 supt. (src) BPERL1S contains the sources for "BIGPERL4", a version of Perl 4.0pl36 that supports large amounts of memory (up to 32MB), and works under Windows 3.1. | | | BIGPERL4 is Perl 4.0pl36 that has been compiled using the Watcom C/386 compiler (a 32-bit, flat-memory model C compiler), which gives this version the following features: * Up to 32MB of memory can be used. | | | A 386/486 with at least 4MB RAM is required, and a third-party memory manager such as QEMM is strongly recommended. |
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http://www.cpan.org/ports/msdos/old/perl4/README.bperl1x
(219 words)
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| | 19.6 Match Memory Models and Other Qualifiers |
| | For example, if you compiled using the flat memory model, make sure you are linking to a library compiled with the flat memory model. | | | ), the choice to use (or not use) shared libraries, and memory models. | | | Similarly, if you are using a debug version of the library, be sure to compile your programs with the same debug settings (see Section 17.5). |
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http://www.roguewave.com/support/docs/hppdocs/tlsug/19.6.html
(130 words)
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| | Creating 32-Bit Flat Memory Model MASM Code for OS/2 2.0 (94577) |
| | MASM versions 6.0, 6.0a, and 6.0b does not include either the required library support for OS/2 operating system calls or a linker capable of producing flat memory model applications. | | | Place the.386 or.486 directive before the.MODEL flat, syscall directive to ensure that your code and data segments are set up correctly for a 32-bit flat memory model application. | | | When combined with the LINK386 utility and DOSCALLS.LIB library provided with OS/2 version 2.0, you can generate a 32-bit flat memory model application for the OS/2 version 2.0 environment. |
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http://www.it-faq.pl/mskb/94/577.HTM
(355 words)
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| | flat out - Idioms - by the Free Dictionary, Thesaurus and Encyclopedia. |
| | if a person or a machine is doing something flat out, they are doing it as fast and with as much energy as they can. | | | This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. | | | if someone says something flat out, they say it in a very clear and direct way, even if it might upset people. |
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http://idioms.thefreedictionary.com/flat+out
(211 words)
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| | [No title] |
| | & ’ " , > % ª> “ ú 1 ó p 4 ¨ .MODEL Directive ¡ , ¨G .MODEL directive specifies a program's memory model and model options (language-specifier) Syntax.MODEL memorymodel [,modeloptions] memorymodel is one of the following (p. |
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http://www2.hawaii.edu/~walbritt/ics312/hllInterface/lecture.ppt
(63 words)
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| | flat foot - Hutchinson encyclopedia article about flat foot |
| | This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. | | | Under the age of one and a half years 97% of children have flat feet, but only 4% have flat feet by the age of ten years. | | | No treatment is required, and modifications to footwear do not alter the shape of the foot. |
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http://encyclopedia.farlex.com/flat+foot
(315 words)
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| | Kevin B Smith's WebLog : Processing Large Interchanges |
| | Because the interchange is sub-divided the memory for each sub-batch may be relinquished in order to keep the memory model flat. | | | In order to keep the memory model flat the engine breaks the interchange into many sub-batches under the scope of a transaction, the transaction is committed only once the interchange has been entirely disassembled successfully. | | | If you consider the implications of this on a large interchanges they are quite interesting... |
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http://blogs.msdn.com/kevinsmi/archive/2005/04/27/412698.aspx
(483 words)
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