DOS Memory Administration: Difference between revisions
Created page with "<br>1024 bytes) (KiB) of "standard memory". The 640 KiB restrict was particular to the IBM Pc and shut compatibles; other machines operating MS-DOS had different limits, [https://thestarsareright.org/index.php/The_Memory_Wave_-_Unlocking_Your_Mind%E2%80%99s_Potential Memory Wave] for instance the Apricot Laptop might have up to 768 KiB and the Sirius Victor 9000, 896 KiB. DOS, while permitting computer users to benefit from giant amounts of low-value memory and new gene..." |
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Latest revision as of 12:32, 21 October 2025
1024 bytes) (KiB) of "standard memory". The 640 KiB restrict was particular to the IBM Pc and shut compatibles; other machines operating MS-DOS had different limits, Memory Wave for instance the Apricot Laptop might have up to 768 KiB and the Sirius Victor 9000, 896 KiB. DOS, while permitting computer users to benefit from giant amounts of low-value memory and new generations of processors. Since DOS has given technique to Microsoft Windows and other 32-bit working techniques not restricted by the unique arbitrary 640 KiB restrict of the IBM Computer, managing the memory of a personal pc no longer requires the user to manually manipulate internal settings and parameters of the system. The 640 KiB limit imposed nice complexity on hardware and software program supposed to avoid it; the bodily memory in a machine could possibly be organized as a mixture of base or typical memory (together with lower memory), upper Memory Wave App, high memory (not the same as upper memory), extended memory, and expanded memory, all handled in alternative ways.
The Intel 8088 processor utilized in the original IBM Pc had 20 deal with traces and so could straight address 1 MiB (220 bytes) of memory. Totally different areas of this deal with space were allotted to totally different kinds of memory used for various functions. Starting at the bottom finish of the tackle house, the Laptop had read/write random entry memory (RAM) put in, which was utilized by DOS and software applications. The first part of this memory was installed on the motherboard of the system (in very early machines, sixty four KiB, later revised to 256 KiB). Additional memory could be added with playing cards plugged into the expansion slots; every card contained straps or switches to control what a part of the handle space accesses memory and devices on that card. On the IBM Laptop, all of the handle area as much as 640 KiB was available for RAM. This part of the deal with space known as "standard memory" since it is accessible to all versions of DOS routinely on startup.
Section 0, the primary 64 KiB of standard memory, can be referred to as low memory space. Normally expansion memory is about to be contiguous within the tackle area with the memory on the motherboard. If there was an unallocated hole between motherboard memory and the enlargement memory, the memory wouldn't be automatically detected as usable by DOS. The upper memory space (UMA) refers back to the address area between 640 and 1024 KiB (0xA0000-0xFFFFF). The 128 KiB region between 0xA0000 and 0xBFFFF was reserved for VGA screen memory and legacy SMM. The 128 KiB area between 0xC0000 and 0xDFFFF was reserved for device Option ROMs, including Video BIOS. The sixty four KiB area between 0xE0000 to 0xEFFFF was reserved for BIOS as decrease BIOS area. The 64 KiB region between 0xF0000 and 0xFFFFF was reserved for BIOS as higher BIOS area. For instance, the monochrome video adapter memory area ran from 704 to 736 KiB (0xB0000-0xB7FFF). If solely a monochrome show adapter was used, the handle house between 0xA0000 and 0xAFFFF might be used for RAM, which can be contiguous with the standard memory.
The system BIOS ROMs must be on the higher finish of the address space as a result of the CPU starting address is mounted by the design of the processor. The beginning handle is loaded into the program counter of the CPU after a hardware reset and will need to have a defined worth that endures after power is interrupted to the system. On reset or energy up, the CPU hundreds the tackle from the system ROM after which jumps to a defined ROM location to start executing the system power-on self-test, and eventually load an working system. Since an expansion card reminiscent of a video adapter, laborious drive controller, or network adapter may use allocations of memory in many of the higher memory areas, configuration of some combinations of playing cards required careful reading of documentation, Memory Wave App or experimentation, to search out card settings and memory mappings that worked. Mapping two devices to use the identical physical memory addresses may result in a stalled or unstable system.
Not all addresses within the higher memory area were utilized in a typical system; unused physical addresses would return undefined and system-dependent information if accessed by the processor. As memory prices declined, application programs corresponding to spreadsheets and laptop-aided drafting were changed to take advantage of more and more bodily memory within the system. Digital memory in the 8088 and 8086 was not supported by the processor hardware, and disk technology of the time would make it too gradual and cumbersome to be sensible. Expanded memory was a system that allowed utility packages to entry more RAM than straight seen to the processor's deal with area. The method was a type of financial institution switching. When additional RAM was wanted, driver software would temporarily make a piece of expanded memory accessible to the processor; when the info in that piece of memory was up to date, one other part might be swapped into the processor's address area.
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