memorymap

0x0     - 0x3FF:    IVT
0x400   - 0x4FF:    BDA
0x500   - 0x7BFF:   Unused - Free
0x7C00  - 0x7DFF:   Boot sector
0x7E00  - 0x7FFFF:  Unused - Free
0x80000 - 0x9FBFF:  Partially free; check EBDA size before use
0x9FC00 - 0x9FFFF:  EBDA
0xA0000 - 0xFFFFF:  VRAM, ROM, VBIOS/BIOS, HW Data, etc (unusable) 

===================== OS Memory Map =====================
0x500 - 0x6FF:	Boot sector copy, used for disk info stuff
0x700 - 0x8FF:	System data area (SDA), contains data required for the OS
0x900 - 0x7BFF:	Reserved for stack (29440 bytes)
0x7C00- 0x7DFF:	Starts with boot sector, later will have Kernel
0x7E00- 0x9FFF:	Reserved for Kernel
0xA000- 0xA3FF:	FAT Copy
0xA400- 0xA7FF: Root Dir Copy
0xA800- 0xABFF: SubDir Copy
0xAC00- 0xFFFF: System (Command Interpreter)
0x10000-0x????: Loaded Program

===================== SDA Structure =====================
0x700 - 0x70F (16 Bytes): DAP (Disk Access Packet)
0x710 - BYTE: BIOS allows LBA
0x711 - WORD: FAT Offset
0x713 - WORD: FAT Dir Offset
0x715 - WORD: FAT Dir Size
0x717 - WORD: FAT FData Offset
0x719 - BYTE: Selected FAT
0x71A - WORD: Cached FAT Sector (Offset)
0x71C - WORD: Cached FAT Root Dir Sector (Offset)
0x71E - WORD: Cached SubDir Sector (FData Offset)