diff --git a/src/arch/i386/prefix/romprefix.S b/src/arch/i386/prefix/romprefix.S
index 4a5bd2e6..ced0f49c 100644
--- a/src/arch/i386/prefix/romprefix.S
+++ b/src/arch/i386/prefix/romprefix.S
@@ -6,412 +6,180 @@
  * table so using a noticeable amount of stack space is a no-no.
  */
 
-/* Define DELAYED_INT when NO_DELAYED_INT is not defined.
- * This allows positive tests instead of tests that contain
- * double negatives, and become confusing.
- */
-#ifndef NO_DELAYED_INT
-#define DELAYED_INT
-#endif
-
-/* We need some unique magic ID, if we defer startup thru the INT18H or INT19H
- * handler. This way, we can check if we have already been installed.
- */
-#ifndef MAGIC
-#define MAGIC		0xE44C
-#endif
-
-/* Hook into INT18H or INT19H handler */
-#ifdef	BOOT_INT18H
-#define BOOT_INT	0x18
-#else
-#define BOOT_INT	0x19
-#endif
-
-#define BOOT_INT_VEC	BOOT_INT*4
-#define SCRATCHVEC	0x300
-
-/* Prefix exit codes.  We store these on the stack so that we will
- * know how to return control to the BIOS when Etherboot exits.
- */
-#define EXIT_VIA_LRET  		0x0
-#define EXIT_VIA_INT_18		0x1
-#define EXIT_VIA_BOOT_INT	0x2
-
 	.text
 	.code16
 	.arch i386
-	.org 0
 	.section ".prefix", "ax", @progbits
-_prefix: 
-	.word 0xAA55			/* BIOS extension signature */
-size:	.byte 0				/* number of 512 byte blocks */
-					/* = number of 256 word blocks */
-					/* filled in by makerom program */
-	jmp	over			/* skip over checksum */
-	.byte 0				/* checksum */
-	jmp	legacyentry		/* alternate entry point +6 */
-					/* used by mknbi-rom */
-
-#ifdef	PCI_PNP_HEADER
-mfgstr:
-	.asciz	"Etherboot"
 	
-#ifdef	PXE_EXPORT
+	.org	0x00
+romheader:
+	.word	0xAA55			/* BIOS extension signature */
+	.byte	_rom_size		/* Size in 512-byte blocks */
+	jmp	init_vector		/* Initialisation vector */
 	.org	0x16
-	.word	UNDIROMID - _prefix
-#endif	/* PXE_EXPORT */
-	
+	.word	undiheader
 	.org	0x18
-	.word	PCI - _prefix
-	.word	PnP - _prefix
+	.word	pciheader
+	.org	0x1a
+	.word	pnpheader
+	.size romheader, . - romheader
 
-PCI: 
-	.ascii	"PCIR"
-	.word 0x0000			/* vendor ID, filled in by makerom */
-	.word 0x0000			/* device ID, filled in by makerom */
-	.word 0x0000			/* pointer to vital product data */
-	.word 0x0018			/* PCI data structure length */
-	.byte 0x00			/* PCI data structure revision */
-	.byte 0x02			/* Device Base Type code */
-	.byte 0x00			/* Device Sub-Type code */
-	.byte 0x00			/* Device Interface Type code */
-	.word 0x0000			/* Image length same as offset 02h */
-	.word 0x0001			/* revision level of code/data */
-	.byte 0x00			/* code type */
-	.byte 0x80			/* indicator (last PCI data structure) */
-	.word 0x0000			/* reserved */
+pciheader:
+	.ascii	"PCIR"			/* Signature */
+	.word	pci_vendor_id		/* Vendor ID */ 
+	.word	pci_device_id		/* Device ID */
+	.word	0x0000			/* pointer to vital product data */
+	.word	pciheader_len		/* PCI data structure length */
+	.byte	0x00			/* PCI data structure revision */
+	.byte	0x02			/* Device Base Type code */
+	.byte	0x00			/* Device Sub-Type code */
+	.byte	0x00			/* Device Interface Type code */
+	.word	_rom_size		/* Image length same as offset 02h */
+	.word	0x0001			/* revision level of code/data */
+	.byte	0x00			/* code type */
+	.byte	0x80			/* Flags (last PCI data structure) */
+	.word	0x0000			/* reserved */
+	.equ pciheader_len, . - pciheader
+	.size pciheader, . - pciheader
 
-PnP:
-	.ascii	"$PnP"
-	.byte 0x01			/* structure revision */
-	.byte 0x02			/* length (in 16 byte increments) */
-	.word 0x0000			/* offset of next header */
-	.byte 0x00			/* Reserved */
-	.byte 0x00			/* checksum filled by makerom */
-	.long 0x00000000		/* Device identifier */
-	.word mfgstr - _prefix
-	.word 0x0			/* pointer to product name */
-					/* filled by makerom */
-	.byte 0x02			/* Device Base Type code */
-	.byte 0x00			/* Device Sub-Type code */
-	.byte 0x00			/* Device Interface Type code */
-	.byte 0x14			/* device indicator */
-	.word 0x0000			/* boot connection vector */
-	.word 0x0000			/* disconnect vector */
-	.word pnpentry - _prefix
-	.word 0x0000			/* reserved */
-	.word 0x0000			/* static resource information vector */
-#ifdef	PXE_EXPORT
-UNDIROMID:
-	.ascii	"UNDI"
-	.byte	UNDIROMID_end - UNDIROMID /* length of structure */
+pnpheader:
+	.ascii	"$PnP"			/* Signature */
+	.byte	0x01			/* Structure revision */
+	.byte	( pnpheader_len	/ 16 )	/* Length (in 16 byte increments) */
+	.word	0x0000			/* Offset of next header */
+	.byte	0x00			/* Reserved */
+	.byte	0x00			/* Checksum */
+	.long	0x00000000		/* Device identifier */
+	.word	mfgstr			/* Manufacturer string */
+	.word	prodstr			/* Product name */
+	.byte	0x02			/* Device base type code */
+	.byte	0x00			/* Device sub-type code */
+	.byte	0x00			/* Device interface type code */
+	.byte	0x54			/* Device indicator */
+	.word	0x0000			/* Boot connection vector */
+	.word	0x0000			/* Disconnect vector */
+	.word	exec_vector		/* Boot execution vector */
+	.word	0x0000			/* Reserved */
+	.word	0x0000			/* Static resource information vector*/
+	.equ pnpheader_len, . - pnpheader
+	.size pnpheader, . - pnpheader
+
+mfgstr:
+	.asciz	"http://etherboot.org"
+	.size mfgstr, . - mfgstr
+prodstr:
+	.asciz	"Etherboot"
+	.size prodstr, . - prodstr
+	
+undiheader:
+	.ascii	"UNDI"			/* Signature */
+	.byte	undiheader_len		/* Length of structure */
 	.byte	0			/* Checksum */
 	.byte	0			/* Structure revision */
-	.byte	0,1,2			/* PXE version 2.1.0 */
-	.word	UNDILoader - _prefix	/* Offset to loader routine */
-	.word	_real_mode_stack_size	/* Stack segment size */
-	.word	_real_mode_stack_size	/* Data segment size */
-	.word	_pxe_stack_size		/* Code segment size */
-	.ascii	"PCIR"
+	.byte	0,1,2			/* PXE version: 2.1.0 */
+	.word	undiloader		/* Offset to loader routine */
+	.word	_data16_size		/* Stack segment size */
+	.word	_data16_size		/* Data segment size */
+	.word	_text16_size		/* Code segment size */
+	.equ undiheader_len, . - undiheader
+	.size undiheader, . - undiheader
 
-	/* The code segment contains our pxe_stack_t plus the PXE and
-	 * RM callback interfaces.  We don't actually use a data
-	 * segment, but we put a nonzero value here to avoid confusing
-	 * things.  16k of stack space should be enough.
-	 *
-	 * When we claim our own memory, we fill out the data segment
-	 * with the address and size of the real-mode stack, so that
-	 * NBPs will free that area of memory for us.  When the UNDI
-	 * loader is used to initialise us, we will never need a
-	 * real-mode stack because we will only ever be called via the
-	 * PXE API, hence our stack is already in base memory.
-	 */
-	.equ	UNDICodeSize, _pxe_stack_size
-	.equ	UNDIDataSize, _real_mode_stack_size
-	.equ	UNDIStackSize, _real_mode_stack_size
-UNDIROMID_end:	
-#endif	/* PXE_EXPORT */
-	
-#endif	/* PCI_PNP_HEADER */
-
-/*
- *	Explicitly specify DI is wrt ES to avoid problems with some BIOSes
- *	Discovered by Eric Biederman
- *	In addition, some BIOSes don't point DI to the string $PnP so
- *	we need another #define to take care of that.
+/* Initialisation vector
+ *
+ * Determine whether or not this is a PnP system via a signature
+ * check.  If it is PnP, return to the PnP BIOS indicating that we are
+ * a boot-capable device; the BIOS will call our boot execution vector
+ * if it wants to boot us.  If it is not PnP, hook INT 19.
  */
-over:	
-#ifdef	DEBUG_ROMPREFIX
-	call	print_bcv
-#endif
-/* Omit this test for ISA cards anyway */
-#ifdef	PCI_PNP_HEADER
-/* Accept old name too for backward compatibility */
-#if	!defined(BBS_BUT_NOT_PNP_COMPLIANT) && !defined(PNP_BUT_NOT_BBS_COMPLIANT)
-	cmpw	$'$'+'P'*256,%es:0(%di)
+init_vector:
+	pushw	%si
+	cmpw	$'$'+'P'*256, %es:0(%di)
 	jne	notpnp
-	cmpw	$'n'+'P'*256,%es:2(%di)
+	cmpw	$'n'+'P'*256, %es:2(%di)
 	jne	notpnp
-#endif	/* BBS_BUT_NOT_PNP_COMPLIANT */
-	movw	$0x20,%ax
-	lret
-#endif	/* PCI_PNP_HEADER */
+ispnp:
+	movw	$ispnp_message, %si
+	jmp	99f
 notpnp:
-#ifdef	DEBUG_ROMPREFIX
-	call	print_notpnp
-#endif
-#ifdef  DELAYED_INT
-	pushw	%ax
 	pushw	%ds
-	xorw	%ax,%ax
-	movw	%ax,%ds			/* access first 64kB segment */
-	movw	SCRATCHVEC+4, %ax	/* check if already installed */
-	cmpw	$MAGIC, %ax		/* check magic word */
-	jz	installed
-	movw	BOOT_INT_VEC, %ax	/* hook into INT18H or INT19H */
-	movw	%ax, SCRATCHVEC
-	movw	BOOT_INT_VEC+2, %ax
-	movw	%ax, SCRATCHVEC+2
-	movw	$start_int - _prefix, %ax
-	movw	%ax, BOOT_INT_VEC
-	movw	%cs,%ax
-	movw	%ax, BOOT_INT_VEC+2
-	movw	$MAGIC, %ax		/* set magic word */
-	movw	%ax, SCRATCHVEC+4
-#ifdef	DEBUG_ROMPREFIX
-	call	print_installed
-#endif
-installed:
+	pushw	$0
 	popw	%ds
-	popw	%ax
-	movw	$0x20,%ax
-	lret
-
-start_int:				/* clobber magic id, so that we will */
-#ifdef	DEBUG_ROMPREFIX
-	call	print_start_int
-#endif
-	xorw	%ax,%ax			/* not inadvertendly end up in an */
-	movw	%ax,%ds			/* endless loop */
-	movw	%ax, SCRATCHVEC+4
-	movw	SCRATCHVEC+2, %ax	/* restore original INT19h handler */
-	movw	%ax, BOOT_INT_VEC+2
-	movw	SCRATCHVEC, %ax
-	movw	%ax, BOOT_INT_VEC
-	pushl	%eax			/* padding */
-	pushw	$EXIT_VIA_BOOT_INT
-	jmp	invoke
-#endif	/* DELAYED_INT */
-
-
-
-	
-legacyentry:
-#ifdef	DEBUG_ROMPREFIX
-	call	print_legacyentry
-#endif
-	pushw	$EXIT_VIA_LRET
-	jmp	invoke
-
-	
-	
-#ifdef PCI_PNP_HEADER
-pnpentry:
-#ifdef	DEBUG_ROMPREFIX
-	call	print_bev
-#endif
-	pushl	%eax			/* padding */
-	pushw	$EXIT_VIA_INT_18
-	jmp	invoke
-#endif /* PCI_PNP_HEADER */
-
-
-invoke:
-	/* Store ROM segment and size on stack */
-	pushw	%ax
-	pushw   %ds
 	pushw	%cs
-	movzbw	%cs:(size-_prefix), %ax
-	shlw	$9, %ax			/* 512-byte blocks */
-	pushw	%ax
-	/* Relocate to free base memory, switch stacks */
-	pushw	$12			/* Preserve exit code & far ret addr */
-	call	prelocate
-	/* We are now running in RAM */
-	popw	%ax			/* padding */
-	movw	%cs, %ax
-	movw	%ax, %ds
-	popw	%ds:(_prefix_rom+2)	/* ROM size */
-	popw	%ds:(_prefix_rom+0)	/* ROM segment */
-	popw	%ds			/* Original %ds */
-	popw	%ax			/* Original %ax */
-	pushw	%ax			/* 4-byte alignment */
-	pushl	$8			/* Preserve exit code & far ret addr */
-	pushw	$0			/* Set null return address */
-	jmp	_start
-	
-
-	.section ".text16", "ax", @progbits
-prefix_exit:
-	popw	%ax			/* padding */
-	popw	%ax			/* %ax = exit code */
-	cmpw	$EXIT_VIA_LRET, %ax
-	jne	1f
-	/* Exit via LRET */
+	pushw	$exec_vector
+	popl	( 0x19 * 4 )
+	popw	%ds
+	movw	$notpnp_message, %si
+99:
+	call	print_message
+	movw	$0x20, %ax
+	popw	%si
 	lret
-1:	addw	$4, %sp			/* Strip padding */
-	cmpw	$EXIT_VIA_BOOT_INT, %ax
-	jne	2f
-	/* Exit via int BOOT_INT */
-	int	$BOOT_INT		/* Try original vector */
-2:	/* Exit via int $0x18 */
-	int	$0x18			/* As per BIOS Boot Spec, next dev */
-prefix_exit_end:
+	.size init_vector, . - init_vector
+
+ispnp_message:
+	.asciz	"Etherboot detected PnP BIOS\r\n"
+	.size ispnp_message, . - ispnp_message
+notpnp_message:
+	.asciz	"Etherboot detected non-PnP BIOS\r\n"
+	.size notpnp_message, . - notpnp_message
+
+/* Boot execution vector
+ *
+ * Called by the PnP BIOS when it wants to boot us, or via the hooked
+ * INT 19 if we detected a non-PnP BIOS.
+ */	
+exec_vector:
+	/* Obtain a reasonably-sized stack */
+	xorw	%ax, %ax
+	movw	%ax, %ss
+	movw	$0x7c00, %sp
+	
+	movw	$exec_message, %si
+	call	print_message
+
+	call	install
+
+	/* Jump to .text16 segment */
+	pushw	%ax
+	pushw	$1f
+	lret
+	.section ".text16", "awx", @progbits
+1:
+	pushl	$main
+	pushw	%cs
+	call	prot_call
+	popl	%eax /* discard */
+
+	/* Boot next device */
+	int	$0x18
 	.previous
 
-	
-
-/* UNDI loader needs to be rewritten to use new mechanism */
-#if 0
-		
-#ifdef 	PXE_EXPORT
-
-#define PXENV_UNDI_LOADER		0x104d
-
-	.section ".prefix"
-UNDILoader:
-	/* Loader API is different to the usual PXE API; there is no
-	 * opcode on the stack.  We arrange the stack to look like a
-	 * normal PXE API call; this makes the Etherboot internals
-	 * cleaner and avoids adding an extra API type just for the
-	 * PXE loader.
-	 */
-	pushw	%bx
-	movw	%sp, %ax		/* Store original %ss:sp */
-	pushw	%ss
-	pushw	%ax
-	pushl	%eax			/* Space for loader structure ptr */
-	pushw	%bp
-	movw	%sp, %bp
-	movw	16(%bp), %ax		/* Copy loader structure ptr */
-	movw	%ax, 2(%bp)
-	movw	18(%bp), %ax
-	movw	%ax, 4(%bp)
-	popw	%bp
-	pushw	$PXENV_UNDI_LOADER	/* PXE 'opcode' */
-	pushl	%eax			/* dummy return address */
-	/* Stack now looks like a normal PXE API call */
-	/* Store ROM segment and size on stack */
-	pushw	%ax
-	pushw	%cs
-	movzbw	%cs:(size-_prefix), %ax
-	shlw	$9, %ax			/* 512-byte blocks */
-	pushw	%ax
-	/* Unpack Etherboot into temporarily claimed base memory */
-	pushw	$20			/* Dummy ret, PXE params, orig ss:sp */
-	call	prelocate
-	popw	%ax			/* discard */
-	popw	%cs:(_prefix_rom+2)	/* ROM size */
-	popw	%cs:(_prefix_rom+0)	/* ROM segment */
-	popw	%ax			/* Original %ax */
-	/* Inhibit automatic deallocation of base memory */
-	movl	$0, %cs:_prefix_image_basemem
-	/* Make PXE API call to Etherboot */
-	pushl	$0x201			/* PXE API version */
-	/* Need to USE_INTERNAL_STACK, since we will call relocate() */
-	pushl	$(EB_OPCODE_PXE|EB_USE_INTERNAL_STACK) /* PXE API call type */
-	call	_entry
-	addw	$18, %sp		/* discard */
-	popw	%bx			/* Restore original %ss:sp */
-	popw	%ss
-	movw	%bx, %sp
-	popw	%bx
-	call	deprelocate
-	lret	$2			/* Skip our PXE 'opcode' */
-#endif	/* PXE_EXPORT */
-
-#endif /* 0 */
-			
-#ifdef DEBUG_ROMPREFIX
-	.section ".prefix"
-
-print_bcv:
-	pushw	%si
-	movw	$1f-_prefix, %si
-	call	print_message
-	popw	%si
-	ret
-1:	.asciz	"ROM detected\r\n"
-
-print_bev:
-	pushw	%si
-	movw	$1f-_prefix, %si
-	call	print_message
-	popw	%si
-	ret
-1:	.asciz	"booting\r\n"
-
-print_notpnp:
-	pushw	%si
-	movw	$1f-_prefix, %si
-	call	print_message
-	popw	%si
-	ret
-1:	.asciz	": Non-PnP BIOS detected!\r\n"
-
-print_legacyentry:
-	pushw	%si
-	movw	$1f-_prefix, %si
-	call	print_message
-	popw	%si
-	ret
-1:	.asciz	"ROM using legacy boot mechanism\r\n"
-
-print_installed:
-	pushw	%si
-	movw	$1f-_prefix, %si
-	call	print_message
-	popw	%si
-	ret
-1:	.ascii	"hooked boot via INT"
-#ifdef	BOOT_INT18H
-	.asciz	"18\r\n"
-#else
-	.asciz	"19\r\n"
-#endif
-
-print_start_int:
-	pushw	%si
-	movw	$1f-_prefix, %si
-	call	print_message
-	popw	%si
-	ret
-1:	.asciz	"booting via hooked interrupt\r\n"
+exec_message:
+	.asciz	"Etherboot starting boot\r\n"
+	.size exec_message, . - exec_message
 
+/* UNDI loader
+ *
+ * Called by an external program to load our PXE stack.
+ */
+undiloader:
+	.size undiloader, . - undiloader
+				
+/* Utility function: print string
+ */
 print_message:
-	pushaw
-	pushw	%ds
-	pushw	%cs
-	popw	%ds
-	pushw	%si
-	movw	$1f-_prefix, %si
-	call	print_string
-	popw	%si
-	call    print_string
-	popw	%ds
-	popaw
-	ret
-1:	.asciz	"Etherboot "
-
-print_string:
-1:	lodsb
-	testb	%al,%al
+	pushw	%ax
+	pushw	%bx
+	pushw	%bp
+	movw    $0x0007, %bx
+1:	cs lodsb
+	testb	%al, %al
 	je	2f
-	movw    $0x0007, %bx            /* page 0, attribute 7 (normal) */
 	movb    $0x0e, %ah              /* write char, tty mode */
 	int     $0x10
 	jmp	1b
-2:	ret
-	
-#endif
+2:	popw	%bp
+	popw	%bx
+	popw	%ax
+	ret
+	.size print_message, . - print_message