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| author | Freya Murphy <freya@freyacat.org> | 2025-03-25 17:36:52 -0400 |
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| committer | Freya Murphy <freya@freyacat.org> | 2025-03-25 17:38:22 -0400 |
| commit | 6af21e6a4f2251e71353562d5df7f376fdffc270 (patch) | |
| tree | de20c7afc9878422c81e34f30c6b010075e9e69a /doc/Memory.txt | |
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initial checkout from wrc
Diffstat (limited to 'doc/Memory.txt')
| -rw-r--r-- | doc/Memory.txt | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/doc/Memory.txt b/doc/Memory.txt new file mode 100644 index 0000000..cecfea3 --- /dev/null +++ b/doc/Memory.txt @@ -0,0 +1,92 @@ +Systems Programming framework memory layout + +Version: @(#)Memory.txt 2.2a +Date: 3/23/25 +--------------------------------------------------------------------------- + +This diagram shows important areas in the first 1MB of memory as seen +by the standalone framework code. + +Each row in the diagram represents 0x100 (256) bytes of memory, except in +"elided" areas (< ... >). The starting address is indicated for each +region in hex; if a CPP #define exists for that region in either +bootstrap.h or x86/bios.h, its name is also given. + + ----------------------- + | Interrupt Vector | 0x00000 + | 256 x 4 bytes | + | (1024, 0x400) | + | | + ----------------------- + | BIOS Data Area (BDA)| 0x00400 BIOS_BDA + ----------------------- + | GDT | 0x00500 GDT_ADDR + | 1024 x 8 bytes | + | (8192, 0x2000) | + | | + < . . . > + | | + ----------------------- + | IDT | 0x02500 IDT_ADDR + | 256 x 8 bytes | + | (2048, 0x800) | + | | + | | + | | + | | + | | + ----------------------- + | Mmap data | 0x02D00 MMAP_ADDR + | | + | | + | | + | | + < . . . > + | | + ----------------------- + | Bootstrap sector 1 | 0x07c00 BOOT_ADDR + | | + ----------------------- + | Bootstrap sector 2 | 0x07e00 PART2_ADDR + | | + ----------------------- + | | 0x08000 + | | + < . . . > + | ^ | + | Bootstrap stack | | + ----------------------- + | | 0x0bc00 BOOT_SP_ADDR + | | + | | + < . . . > + | OS stack | + ----------------------- + | Operating System | 0x10000 TARGET_ADDR, TARGET_STACK + | (size varies) | + | | + < . . . > + | | + ----------------------- + | User Code Blob | 0x30000 + | (size varies) | + | | + < . . . > + | | + ----------------------- + | Extended BIOS Data | 0x9fc00 + | Area (EBDA) | + | | + < . . . > + | | + ----------------------- + | Video memory | 0xb8000 VID_BASE_ADDR + | | + < . . . > + | | + ----------------------- + | The BIOS | 0xf0000 + | | + < . . . > + | | + ----------------------- 0xfffff |