diff --git a/docs/bootloader.md b/docs/bootloader.md
index 229a310..ee3764f 100644
--- a/docs/bootloader.md
+++ b/docs/bootloader.md
@@ -14,6 +14,19 @@
 | 0x80000 | 0x9ffff | EDBA, partially usable    |
 | 0xa0000 | 0xfffff | unusable                  |
 
+## Bootsector layout
+
+(all addresses are offsets from 0x7C00)
+
+| start  | end    | use               |
+|--------|--------|-------------------|
+| 0x0000 | ?      | Bootloader code   |
+| ?      | 0x0193 | _padding_         |
+| 0x0194 | 0x01bd | SFS header        |
+| 0x01be | ?      | _padding_         |
+| ?      | 0x01fd | data              |
+| 0x01fe | 0x01ff | 0x55AA boot magic |
+
 ## Drive layout
 
 The first 512 bytes are the bootloader, right after that the 32-bit kernel ELF-file, this kernel can be 32KiB big. In the future, this "kernel" can be replaced by a second stage of the bootloader.