Added ISO-9660 boot sector description.

[reactos.git] / freeldr / notes.txt

diff --git a/freeldr/notes.txt b/freeldr/notes.txt
index 0402975..dae66a2 100644 (file)
--- a/freeldr/notes.txt
+++ b/freeldr/notes.txt
@@ -34,10 +34,32 @@ A000:0000 - FFFF:FFFF: reserved
 
 FreeLoader Boot Process
 
-Boot Sector
+FAT 12/16/32 Boot Sector
+
+       The BIOS loads the boot sector at 0000:7C00. The FAT32 boot sector
+relocates itself higher in memory at 9000:0000 and loads it's extra sector
+at 9000:0200 and then looks for freeldr.sys on the file system. Once found
+it loads freeldr.sys to 0000:7E00 and then jumps to it's entry point at
+0000:8000. The FAT12/16 boot sector does no relocation, it just searches for
+the freeldr.sys and loads the first 512 bytes to 0000:7E00. This extra code
+enables it to fully navigate the file allocation table. Then it loads
+freeldr.sys to 0000:7E00 and jumps to it's entry point at 0000:8000. Before
+FreeLoader gets control the boot sector saves the screen contents to a buffer
+at 9000:8000 and the cursor x & y position to bytes at 9000:8FA0 & 9000:8FA1
+respectively.
+
+
+ISO-9660 (CD-ROM) Boot Sector
+
+       The BIOS loads the boot sector (2048 bytes) at 0000:7C00. First, the
+boot sector relocates itself to 0000:7000 (up to 0000:7800). Then it looks
+for the I386 directory and makes it the current directory. Next it looks for
+FREELDR.SYS and loads it at 0000:8000. Finally it restores the boot drive
+number in the DL register and jumps to FreeLoader's entry point at 0000:8000.
 
-       The BIOS loads the boot sector at 0000:7C00. The FAT32 boot sector relocates itself higher in memory at 9000:0000 and loads it's extra sector at 9000:0200 and then looks for freeldr.sys on the file system. Once found it loads freeldr.sys to 0000:7E00 and then jumps to it's entry point at 0000:8000. The FAT12/16 boot sector does no relocation, it just searches for the freeldr.sys and loads the first 512 bytes to 0000:7E00. This extra code enables it to fully navigate the file allocation table. Then it loads freeldr.sys to 0000:7E00 and jumps to it's entry point at 0000:8000. Before FreeLoader gets control the boot sector saves the screen contents to a buffer at 9000:8000 and the cursor x & y position to bytes at 9000:8FA0 & 9000:8FA1 respectively.
 
 FreeLoader Initialization
 
-       When FreeLoader gets control it saves the boot drive, passed to it in the DL register, and sets up the stack, enables protected mode, and calls BootMain().
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+       When FreeLoader gets control it saves the boot drive, passed to it in
+the DL register, and sets up the stack, enables protected mode, and calls
+BootMain().
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