Document the COM32R format

1 files changed, 11 insertions, 8 deletions

diff --git a/doc/comboot.txt b/doc/comboot.txt
index f5fefdaf..1b087a16 100644
--- a/doc/comboot.txt
+++ b/doc/comboot.txt
@@ -51,25 +51,28 @@ program), or execute INT 20h or INT 21h AH=00h or INT 21h AH=4Ch.
 If compatiblity with Syslinux 1.xx is desired, use INT 20h.
 
 
-	++++ COM32 file format ++++
+	++++ COM32R file format ++++
 
-A COM32 file is a raw binary file containing 32-bit code.  It should
-be linked to run at address 0x101000, and should not contain any
-segment references.  It will be run in flat-memory 32-bit protected
+A COM32R file is a raw binary file containing 32-bit code.  It should
+be self-relocating, as it will be loaded by the Syslinux core at any
+4K aligned address.  It will be run in flat-memory 32-bit protected
 mode.  Under Syslinux, it will be run in CPL 0, however, since it may
 be possible to create a COM32 execution engine that would run under
 something like Linux DOSEMU, it is recommended that the code does not
 assume CPL 0 unless absolutely necessary.
 
-It is highly recommended that every COM32 program begins with the byte
-sequence B8 FF 4C CD 21 (mov eax,21cd4cffh) as a magic number.
+It is highly recommended that every COM32R program begins with the byte
+sequence B8 FE 4C CD 21 (mov eax,21cd4cfeh) as a magic number.
 
-A COM32 file should have extension ".c32".
+The COM32R format replaces the earlier COM32 format, which was linked
+to a fixed address (0x101000).
+
+A COM32R file should have extension ".c32".
 
 On startup, CS will be set up as a flat 32-bit code segment, and DS ==
 ES == SS will be set up as the equivalent flat 32-bit data segment.
 FS and GS are reserved for future use and are currently initialized to
-zero.  A COM32 image should not assume any particular values of
+zero.  A COM32R image should not assume any particular values of
 segment selectors.
 
 ESP is set up at the end of available memory and also serves as