GNU Info

(grub.info)Memory map

---

Next: Embedded data Up: Internals

---

Enter node , (file) or (file)node

The memory map of various components
====================================

   GRUB consists of two distinct components, called "stages", which are
loaded at different times in the boot process. Because they run
mutual-exclusively, sometimes a memory area overlaps with another
memory area. And, even in one stage, a single memory area can be used
for various purposes, because their usages are mutually exclusive.

   Here is the memory map of the various components:

0 to 4K-1
     BIOS and real mode interrupts

0x07BE to 0x07FF
     Partition table passed to another boot loader

down from 8K-1
     Real mode stack

0x2000 to ?
     The optional Stage 1.5 is loaded here

0x2000 to 0x7FFF
     Command-line buffer for Multiboot kernels and modules

0x7C00 to 0x7DFF
     Stage 1 is loaded here by BIOS or another boot loader

0x7F00 to 0x7F42
     LBA drive parameters

0x8000 to ?
     Stage2 is loaded here

The end of Stage 2 to 416K-1
     Heap, in particular used for the menu

down from 416K-1
     Protected mode stack

416K to 448K-1
     Filesystem buffer

448K to 479.5K-1
     Raw device buffer

479.5K to 480K-1
     512-byte scratch area

480K to 512K-1
     Buffers for various functions, such as password, command-line, cut
     and paste, and completion.

The last 1K of lower memory
     Disk swapping code and data

   See the file `stage2/shared.h', for more information.