/* Physical memory layout on IBM compatible PCs. Only the major, fixed memory * areas are detailed here. Known addresses of the BIOS data area are defined * in . The map upper memory area (UMA) is only roughly defined * since the UMA sections may vary in size and locus. * * Created: March 2005, Jorrit N. Herder */ /* I/O-mapped peripherals. I/O addresses are different from memory addresses * due to the I/O signal on the ISA bus. Individual I/O ports are defined by * the drivers that use them or looked up with help of the BIOS. */ #define IO_MEMORY_BEGIN 0x0000 #define IO_MEMORY_END 0xFFFF /* Physical memory layout. Design decisions made for the earliest PCs, caused * memory to be broken broken into the following four basic pieces: * - Conventional or base memory: first 640 KB (incl. BIOS data, see below); * The top of conventional memory is often used by the BIOS to store data. * - Upper Memory Area (UMA): upper 384 KB of the first megabyte of memory; * - High Memory Area (HMA): ~ first 64 KB of the second megabyte of memory; * - Extended Memory: all the memory above first megabyte of memory. * The high memory area overlaps with the first 64 KB of extended memory, but * is different from the rest of extended memory because it can be accessed * when the processor is in real mode. */ #define BASE_MEM_BEGIN 0x000000 #define BASE_MEM_TOP 0x090000 #define BASE_MEM_END 0x09FFFF #define UPPER_MEM_BEGIN 0x0A0000 #define UPPER_MEM_END 0x0FFFFF #define HIGH_MEM_BEGIN 0x100000 #define HIGH_MEM_END 0x10FFEF #define EXTENDED_MEM_BEGIN 0x100000 #define EXTENDED_MEM_END ((unsigned) -1) /* The logical memory map of the first 1.5 MB is as follows (hexadecimals): * * offset [size] (id) = memory usage * ------------------------------------------------------------------------ * 000000 [00400] (I) = Real-Mode Interrupt Vector Table (1024 B) * 000400 [00100] (B) = BIOS Data Area (256 B) * 000800 [00066] (W) = 80286 Loadall workspace * 010000 [10000] (c) = Real-Mode Compatibility Segment (64 KB) * 020000 [70000] (.) = Program-accessible memory (free) * 090000 [10000] (E) = BIOS Extension * 0A0000 [10000] (G) = Graphics Mode Video RAM * 0B0000 [08000] (M) = Monochrome Text Mode Video RAM * 0B8000 [08000] (C) = Color Text Mode Video RAM * 0C0000 [08000] (V) = Video ROM BIOS (would be "a" in PS/2) * 0C8000 [18000] (a) = Adapter ROM + special-purpose RAM (free UMA space) * 0E0000 [10000] (r) = PS/2 Motherboard ROM BIOS (free UMA in non-PS/2) * 0F0000 [06000] (R) = Motherboard ROM BIOS * 0F6000 [08000] (b) = IBM Cassette BASIC ROM ("R" in IBM compatibles) * 0FD000 [02000] (R) = Motherboard ROM BIOS * 100000 [.....] (.) = Extended memory, program-accessible (free) * 100000 [0FFEF] (h) = High Memory Area (HMA) * * * Conventional (Base) Memory: * * : [~~~~~16 KB~~~~][~~~~~16 KB~~~~][~~~~~16 KB~~~~][~~~~~16 KB~~~~] * : 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F--- * 000000: IBW............................................................. * 010000: cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc * 020000: ................................................................ * 030000: ................................................................ * 040000: ................................................................ * 050000: ................................................................ * 060000: ................................................................ * 070000: ................................................................ * 080000: ................................................................ * 090000: EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE * * Upper Memory Area (UMA): * * : 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F--- * 0A0000: GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG * 0B0000: MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC * 0C0000: VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa * 0D0000: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa * 0E0000: rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr * 0F0000: RRRRRRRRRRRRRRRRRRRRRRRRbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbRRRRRRRR * * Extended Memory: * * : 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F--- * 100000: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh. * 110000: ................................................................ * 120000: ................................................................ * 130000: ................................................................ * 140000: ................................................................ * 150000: ................................................................ * 160000: ................................................................ * 170000: ................................................................ * * Source: The logical memory map was partly taken from the book "Upgrading * & Repairing PCs Eight Edition", Macmillan Computer Publishing. */ /* The bottom part of conventional or base memory is occupied by BIOS data. * The BIOS memory can be distinguished in two parts: * o The first the first 1024 bytes of addressable memory contains the BIOS * real-mode interrupt vector table (IVT). The table is used to access BIOS * hardware services in real-mode by loading a interrupt vector and issuing * an INT instruction. Some vectors contain BIOS data that can be retrieved * directly and are useful in protected-mode as well. * o The BIOS data area is located directly above the interrupt vectors. It * comprises 256 bytes of memory. These data are used by the device drivers * to retrieve hardware details, such as I/O ports to be used. */ #define BIOS_MEM_BEGIN 0x00000 /* all BIOS memory */ #define BIOS_MEM_END 0x004FF #define BIOS_IVT_BEGIN 0x00000 /* BIOS interrupt vectors */ #define BIOS_IVT_END 0x003FF #define BIOS_DATA_BEGIN 0x00400 /* BIOS data area */ #define BIOS_DATA_END 0x004FF /* The base memory is followed by 384 KB reserved memory located at the top of * the first MB of physical memory. This memory is known as the upper memory * area (UMA). It is used for memory-mapped peripherals, such as video RAM, * adapter BIOS (adapter ROM and special purpose RAM), and the motherboard * BIOS (I/O system, Power-On Self Test, bootstrap loader). The upper memory * can roughly be distinguished in three parts: * * o The first 128K of the upper memory area (A0000-BFFFF) is reserved for use * by memory-mapped video adapters. Hence, it is also called Video RAM. The * display driver can directly write to this memory and request the hardware * to show the data on the screen. */ #define UMA_VIDEO_RAM_BEGIN 0xA0000 /* video RAM */ #define UMA_VIDEO_RAM_END 0xBFFFF #define UMA_GRAPHICS_RAM_BEGIN 0xA0000 /* graphics RAM */ #define UMA_GRAPHICS_RAM_END 0xAFFFF #define UMA_MONO_TEXT_BEGIN 0xB0000 /* monochrome text */ #define UMA_MONO_TEXT_END 0xB7FFF #define UMA_COLOR_TEXT_BEGIN 0xB8000 /* color text */ #define UMA_COLOR_TEXT_END 0xBFFFF /* o The next 128K (the memory range C0000-DFFFF) is reserved for the adapter * BIOS that resides in the ROM on some adapter boards. Most VGA-compatible * video adapters use the first 32 KB of this area for their on-board BIOS. * The rest can be used by any other adapters. The IDE controller often * occupies the second 32 KB. */ #define UMA_ADAPTER_BIOS_BEGIN 0xC0000 /* adapter BIOS */ #define UMA_ADAPTER_BIOS_END 0xDFFFF #define UMA_VIDEO_BIOS_BEGIN 0xC0000 /* video adapter */ #define UMA_VIDEO_BIOS_END 0xC7FFF #define UMA_IDE_HD_BIOS_BEGIN 0xC8000 /* IDE hard disk */ #define UMA_IDE_HD_BIOS_END 0xCBFFF /* o The last 128K of the upper memory area (E0000-FFFFF) is reserved for * motherboard BIOS (Basic I/O System). The POST (Power-On Self Test) and * bootstrap loader also reside in this space. The memory falls apart in * two areas: Plug & Play BIOS data and the system BIOS data. */ #define UMA_MB_BIOS_BEGIN 0xE0000 /* motherboard BIOS */ #define UMA_MB_BIOS_END 0xFFFFF #define UMA_PNP_ESCD_BIOS_BEGIN 0xE0000 /* PnP extended data */ #define UMA_PNP_ESCD_BIOS_END 0xEFFFF #define UMA_SYSTEM_BIOS_BEGIN 0xF0000 /* system BIOS */ #define UMA_SYSTEM_BIOS_END 0xFFFFF