---
 core/isolinux.asm |   33 +++++++++++++++++++++++++++++++++
 core/layout.inc   |    7 +++++++
 core/parsecmd.inc |    8 ++++++++
 3 files changed, 48 insertions(+)

--- a/core/isolinux.asm
+++ b/core/isolinux.asm
@@ -20,6 +20,9 @@
 ; ****************************************************************************
 
 %define IS_ISOLINUX 1
+
+; %define DEBUG_DISKIO
+
 %include "head.inc"
 
 ;
@@ -964,10 +967,40 @@ getlinsec_cdrom:
 		; INT 13h with retry
 xint13:		mov byte [RetryCount],retry_count
 .try:		pushad
+%ifdef DEBUG_DISKIO
+		pushad
+		mov cx,16
+.zap:
+		lodsb
+		call writehex2
+		mov al,' '
+		call writechr
+		loop .zap
+		mov ah,0
+		int 16h
+		popad
+%endif
 		; seen buggy bios that overwrites buffer address on error...
 		push dword [dapa + 4]
 		call int13
 		pop dword [dapa + 4]
+%ifdef DEBUG_DISKIO
+		pushad
+		pushf
+		push ax
+		mov al,':'
+		call writechr
+		mov al,' '
+		call writechr
+		pop ax
+		sbb al,al
+		call writehex4
+		call crlf
+		mov ah,0
+		int 16h
+		popf
+		popad
+%endif
 		jc .error
 .noerror:
 		add sp,byte 8*4			; Clean up stack
--- a/core/layout.inc
+++ b/core/layout.inc
@@ -56,6 +56,11 @@ RBFG_brainfuck:	resb 2048		; Bigger than
 
 		section .bss2		write nobits align=16
 
+%ifdef IS_ISOLINUX
+		; Normal bss...
+		section .bss1		write nobits align=16
+%endif
+
 		section .text		exec write progbits align=16
 		section .bcopyxx	exec write progbits align=16
 		section .data		write progbits align=16
@@ -68,8 +73,10 @@ RBFG_brainfuck:	resb 2048		; Bigger than
 		; the spillover from the last fractional sector load.
 		section .uibss		write nobits align=16
 
+%ifndef IS_ISOLINUX
 		; Normal bss...
 		section .bss1		write nobits align=16
+%endif
 
 		; Symbols from linker script
 %macro SECINFO 1
--- a/core/parsecmd.inc
+++ b/core/parsecmd.inc
@@ -121,6 +121,14 @@ KbdMap		resb 256		; Keyboard map
 FKeyName	resb MAX_FKEYS*FILENAME_MAX	; File names for F-key help
 KernelCNameLen	resw 1			; Length of unmangled kernel name
 InitRDCNameLen	resw 1			; Length of unmangled initrd name
+
+%if IS_ISOLINUX
+%ifdef DEBUG_MESSAGES
+; we need to rearrange memory a bit to make isolinux-debug.bin fit
+		section .bss
+%endif
+%endif
+
 %if IS_SYSLINUX
 KernelName      resb FILENAME_MAX+1	; Mangled name for kernel
 KernelCName     resb FILENAME_MAX+2	; Unmangled kernel name