include/arch/i386/memory.h

   1 /* Physical memory layout on IBM compatible PCs. Only the major, fixed memory
   2  * areas are detailed here. Known addresses of the BIOS data area are defined
   3  * in <ibm/bios.h>. The map upper memory area (UMA) is only roughly defined
   4  * since the UMA sections may vary in size and locus.
   5  *
   6  * Created: March 2005, Jorrit N. Herder
   7  */
   8
   9 /* I/O-mapped peripherals. I/O addresses are different from memory addresses
  10  * due to the I/O signal on the ISA bus. Individual I/O ports are defined by
  11  * the drivers that use them or looked up with help of the BIOS.
  12  */
  13 #define IO_MEMORY_BEGIN             0x0000
  14 #define IO_MEMORY_END               0xFFFF
  15
  16
  17 /* Physical memory layout. Design decisions made for the earliest PCs, caused
  18  * memory to be broken broken into the following four basic pieces:
  19  *  - Conventional or base memory: first 640 KB (incl. BIOS data, see below);
  20  *    The top of conventional memory is often used by the BIOS to store data.
  21  *  - Upper Memory Area (UMA): upper 384 KB of the first megabyte of memory;
  22  *  - High Memory Area (HMA): ~ first 64 KB of the second megabyte of memory;
  23  *  - Extended Memory: all the memory above first megabyte of memory.
  24  * The high memory area overlaps with the first 64 KB of extended memory, but
  25  * is different from the rest of extended memory because it can be accessed
  26  * when the processor is in real mode.
  27  */
  28 #define BASE_MEM_BEGIN            0x000000
  29 #define BASE_MEM_TOP              0x090000
  30 #define BASE_MEM_END              0x09FFFF
  31
  32 #define UPPER_MEM_BEGIN           0x0A0000
  33 #define UPPER_MEM_END             0x0FFFFF
  34
  35 #define HIGH_MEM_BEGIN            0x100000
  36 #define HIGH_MEM_END              0x10FFEF
  37
  38 #define EXTENDED_MEM_BEGIN        0x100000
  39 #define EXTENDED_MEM_END    ((unsigned) -1)
  40
  41
  42 /* The logical memory map of the first 1.5 MB is as follows (hexadecimals):
  43  *
  44  * offset [size]  (id) = memory usage
  45  * ------------------------------------------------------------------------
  46  * 000000 [00400] (I) = Real-Mode Interrupt Vector Table (1024 B)
  47  * 000400 [00100] (B) = BIOS Data Area (256 B)
  48  * 000800 [00066] (W) = 80286 Loadall workspace
  49  * 010000 [10000] (c) = Real-Mode Compatibility Segment (64 KB)
  50  * 020000 [70000] (.) = Program-accessible memory (free)
  51  * 090000 [10000] (E) = BIOS Extension
  52  * 0A0000 [10000] (G) = Graphics Mode Video RAM
  53  * 0B0000 [08000] (M) = Monochrome Text Mode Video RAM
  54  * 0B8000 [08000] (C) = Color Text Mode Video RAM
  55  * 0C0000 [08000] (V) = Video ROM BIOS (would be "a" in PS/2)
  56  * 0C8000 [18000] (a) = Adapter ROM + special-purpose RAM (free UMA space)
  57  * 0E0000 [10000] (r) = PS/2 Motherboard ROM BIOS (free UMA in non-PS/2)
  58  * 0F0000 [06000] (R) = Motherboard ROM BIOS
  59  * 0F6000 [08000] (b) = IBM Cassette BASIC ROM ("R" in IBM compatibles)
  60  * 0FD000 [02000] (R) = Motherboard ROM BIOS
  61  * 100000 [.....] (.) = Extended memory, program-accessible (free)
  62  * 100000 [0FFEF] (h) = High Memory Area (HMA)
  63  *
  64  *
  65  * Conventional (Base) Memory:
  66  *
  67  *       : [~~~~~16 KB~~~~][~~~~~16 KB~~~~][~~~~~16 KB~~~~][~~~~~16 KB~~~~]
  68  *       : 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F---
  69  * 000000: IBW.............................................................
  70  * 010000: cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
  71  * 020000: ................................................................
  72  * 030000: ................................................................
  73  * 040000: ................................................................
  74  * 050000: ................................................................
  75  * 060000: ................................................................
  76  * 070000: ................................................................
  77  * 080000: ................................................................
  78  * 090000: EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
  79  *
  80  * Upper Memory Area (UMA):
  81  *
  82  *       : 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F---
  83  * 0A0000: GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG
  84  * 0B0000: MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
  85  * 0C0000: VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
  86  * 0D0000: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
  87  * 0E0000: rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
  88  * 0F0000: RRRRRRRRRRRRRRRRRRRRRRRRbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbRRRRRRRR
  89  *
  90  * Extended Memory:
  91  *
  92  *       : 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F---
  93  * 100000: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh.
  94  * 110000: ................................................................
  95  * 120000: ................................................................
  96  * 130000: ................................................................
  97  * 140000: ................................................................
  98  * 150000: ................................................................
  99  * 160000: ................................................................
 100  * 170000: ................................................................
 101  *
 102  * Source: The logical memory map was partly taken from the book "Upgrading
 103  *         & Repairing PCs Eight Edition", Macmillan Computer Publishing.
 104  */
 105
 106
 107 /* The bottom part of conventional or base memory is occupied by BIOS data.
 108  * The BIOS memory can be distinguished in two parts:
 109  * o The first the first 1024 bytes of addressable memory contains the BIOS
 110  *   real-mode interrupt vector table (IVT). The table is used to access BIOS
 111  *   hardware services in real-mode by loading a interrupt vector and issuing
 112  *   an INT instruction. Some vectors contain BIOS data that can be retrieved
 113  *   directly and are useful in protected-mode as well.
 114  * o The BIOS data area is located directly above the interrupt vectors. It
 115  *   comprises 256 bytes of memory. These data are used by the device drivers
 116  *   to retrieve hardware details, such as I/O ports to be used.
 117  */
 118 #define BIOS_MEM_BEGIN             0x00000      /* all BIOS memory */
 119 #define BIOS_MEM_END               0x004FF
 120 #define   BIOS_IVT_BEGIN           0x00000      /* BIOS interrupt vectors */
 121 #define   BIOS_IVT_END             0x003FF
 122 #define   BIOS_DATA_BEGIN          0x00400      /* BIOS data area */
 123 #define   BIOS_DATA_END            0x004FF
 124
 125 /* The base memory is followed by 384 KB reserved memory located at the top of
 126  * the first MB of physical memory. This memory is known as the upper memory
 127  * area (UMA). It is used for memory-mapped peripherals, such as video RAM,
 128  * adapter BIOS (adapter ROM and special purpose RAM), and the motherboard
 129  * BIOS (I/O system, Power-On Self Test, bootstrap loader). The upper memory
 130  * can roughly be distinguished in three parts:
 131  *
 132  * o The first 128K of the upper memory area (A0000-BFFFF) is reserved for use
 133  *   by memory-mapped video adapters. Hence, it is also called Video RAM. The
 134  *   display driver can directly write to this memory and request the hardware
 135  *   to show the data on the screen.
 136  */
 137 #define UMA_VIDEO_RAM_BEGIN        0xA0000      /* video RAM */
 138 #define UMA_VIDEO_RAM_END          0xBFFFF
 139 #define   UMA_GRAPHICS_RAM_BEGIN   0xA0000      /* graphics RAM */
 140 #define   UMA_GRAPHICS_RAM_END     0xAFFFF
 141 #define   UMA_MONO_TEXT_BEGIN      0xB0000      /* monochrome text */
 142 #define   UMA_MONO_TEXT_END        0xB7FFF
 143 #define   UMA_COLOR_TEXT_BEGIN     0xB8000      /* color text */
 144 #define   UMA_COLOR_TEXT_END       0xBFFFF
 145
 146 /* o The next 128K (the memory range C0000-DFFFF) is reserved for the adapter
 147  *   BIOS that resides in the ROM on some adapter boards. Most VGA-compatible
 148  *   video adapters use the first 32 KB of this area for their on-board BIOS.
 149  *   The rest can be used by any other adapters. The IDE controller often
 150  *   occupies the second 32 KB.
 151  */
 152 #define UMA_ADAPTER_BIOS_BEGIN     0xC0000      /* adapter BIOS */
 153 #define UMA_ADAPTER_BIOS_END       0xDFFFF
 154 #define   UMA_VIDEO_BIOS_BEGIN     0xC0000      /* video adapter */
 155 #define   UMA_VIDEO_BIOS_END       0xC7FFF
 156 #define   UMA_IDE_HD_BIOS_BEGIN    0xC8000      /* IDE hard disk */
 157 #define   UMA_IDE_HD_BIOS_END      0xCBFFF
 158
 159 /* o The last 128K of the upper memory area (E0000-FFFFF) is reserved for
 160  *   motherboard BIOS (Basic I/O System). The POST (Power-On Self Test) and
 161  *   bootstrap loader also reside in  this space. The memory falls apart in
 162  *   two areas: Plug & Play BIOS data and the system BIOS data.
 163  */
 164 #define UMA_MB_BIOS_BEGIN          0xE0000      /* motherboard BIOS */
 165 #define UMA_MB_BIOS_END            0xFFFFF
 166 #define   UMA_PNP_ESCD_BIOS_BEGIN  0xE0000      /* PnP extended data */
 167 #define   UMA_PNP_ESCD_BIOS_END    0xEFFFF
 168 #define   UMA_SYSTEM_BIOS_BEGIN    0xF0000      /* system BIOS */
 169 #define   UMA_SYSTEM_BIOS_END      0xFFFFF
 170
 171