diff --git a/src/arch/i386/core/relocate.c b/src/arch/i386/core/relocate.c
index b9b02944..5fbf2d2c 100644
--- a/src/arch/i386/core/relocate.c
+++ b/src/arch/i386/core/relocate.c
@@ -33,8 +33,10 @@ extern char _etextdata[];
 /**
  * Relocate iPXE
  *
- * @v ix86		x86 register dump from prefix
- * @ret ix86		x86 registers to return to prefix
+ * @v ebp		Maximum address to use for relocation
+ * @ret esi		Current physical address
+ * @ret edi		New physical address
+ * @ret ecx		Length to copy
  *
  * This finds a suitable location for iPXE near the top of 32-bit
  * address space, and returns the physical address of the new location
@@ -59,7 +61,7 @@ __asmcall void relocate ( struct i386_all_regs *ix86 ) {
 
 	/* Determine maximum usable address */
 	max = MAX_ADDR;
-	if ( ix86->regs.ebp && ( ix86->regs.ebp < max ) ) {
+	if ( ix86->regs.ebp < max ) {
 		max = ix86->regs.ebp;
 		DBG ( "Limiting relocation to [0,%lx)\n", max );
 	}
diff --git a/src/arch/i386/firmware/pcbios/memmap.c b/src/arch/i386/firmware/pcbios/memmap.c
index cf659226..0937a7ce 100644
--- a/src/arch/i386/firmware/pcbios/memmap.c
+++ b/src/arch/i386/firmware/pcbios/memmap.c
@@ -63,6 +63,10 @@ struct e820_entry {
 static struct e820_entry __bss16 ( e820buf );
 #define e820buf __use_data16 ( e820buf )
 
+/** We are running during POST; inhibit INT 15,e820 and INT 15,e801 */
+uint8_t __bss16 ( memmap_post );
+#define memmap_post __use_data16 ( memmap_post )
+
 /**
  * Get size of extended memory via INT 15,e801
  *
@@ -74,6 +78,12 @@ static unsigned int extmemsize_e801 ( void ) {
 	unsigned int flags;
 	unsigned int extmem;
 
+	/* Inhibit INT 15,e801 during POST */
+	if ( memmap_post ) {
+		DBG ( "INT 15,e801 not available during POST\n" );
+		return 0;
+	}
+
 	__asm__ __volatile__ ( REAL_CODE ( "stc\n\t"
 					   "int $0x15\n\t"
 					   "pushfw\n\t"
@@ -164,6 +174,12 @@ static int meme820 ( struct memory_map *memmap ) {
 	unsigned int flags;
 	unsigned int discard_D;
 
+	/* Inhibit INT 15,e820 during POST */
+	if ( memmap_post ) {
+		DBG ( "INT 15,e820 not available during POST\n" );
+		return -ENOTTY;
+	}
+
 	/* Clear the E820 buffer.  Do this once before starting,
 	 * rather than on each call; some BIOSes rely on the contents
 	 * being preserved between calls.
diff --git a/src/arch/i386/prefix/exeprefix.S b/src/arch/i386/prefix/exeprefix.S
index acd3f83c..cb61287d 100644
--- a/src/arch/i386/prefix/exeprefix.S
+++ b/src/arch/i386/prefix/exeprefix.S
@@ -114,7 +114,7 @@ _exe_start:
 	call	alloc_basemem
 	xorl	%esi, %esi
 	movl	$EXE_DECOMPRESS_ADDRESS, %edi
-	xorl	%ebp, %ebp
+	orl	$0xffffffff, %ebp	/* Allow arbitrary relocation */
 	call	install_prealloc
 
 	/* Set up real-mode stack */
diff --git a/src/arch/i386/prefix/libprefix.S b/src/arch/i386/prefix/libprefix.S
index 0bd80b0a..197a86bc 100644
--- a/src/arch/i386/prefix/libprefix.S
+++ b/src/arch/i386/prefix/libprefix.S
@@ -622,7 +622,7 @@ install:
 	/* Image destination = default */
 	xorl	%edi, %edi
 	/* Allow arbitrary relocation */
-	xorl	%ebp, %ebp
+	orl	$0xffffffff, %ebp
 	/* Install text and data segments */
 	call	install_prealloc
 	/* Restore registers and return */
@@ -642,7 +642,9 @@ install:
  *   %bx  : .data16 segment address
  *   %esi : Image source physical address (or zero for %cs:0000)
  *   %edi : Decompression temporary area physical address (or zero for default)
- *   %ebp : Maximum end address for relocation (or zero for no maximum)
+ *   %ebp : Maximum end address for relocation
+ *          - 0xffffffff for no maximum
+ *          - 0x00000000 to inhibit use of INT 15,e820 and INT 15,e801
  * Corrupts:
  *   none
  ****************************************************************************
@@ -796,6 +798,13 @@ payload_death_message:
 	movw	%ax, (init_librm_vector+2)
 	lcall	*init_librm_vector
 
+	/* Inhibit INT 15,e820 and INT 15,e801 if applicable */
+	testl	%ebp, %ebp
+	jnz	1f
+	incb	memmap_post
+	decl	%ebp
+1:
+
 	/* Call relocate() to determine target address for relocation.
 	 * relocate() will return with %esi, %edi and %ecx set up
 	 * ready for the copy to the new location.
diff --git a/src/arch/i386/prefix/romprefix.S b/src/arch/i386/prefix/romprefix.S
index 35d037ef..18fef75e 100644
--- a/src/arch/i386/prefix/romprefix.S
+++ b/src/arch/i386/prefix/romprefix.S
@@ -445,7 +445,7 @@ no_pmm:
 	 * picked up by the initial shell prompt, and we will drop
 	 * into a shell.
 	 */
-	movl	$0xa0000, %ebp	/* Inhibit relocation during POST */
+	xorl	%ebp, %ebp	/* Inhibit use of INT 15,e820 and INT 15,e801 */
 	pushw	%cs
 	call	exec
 2:
@@ -630,7 +630,7 @@ decompress_to:
  * Called by the PnP BIOS when it wants to boot us.
  */
 bev_entry:
-	xorl	%ebp, %ebp	/* Allow relocation */
+	orl	$0xffffffff, %ebp	/* Allow arbitrary relocation */
 	pushw	%cs
 	call	exec
 	lret
@@ -665,7 +665,7 @@ int19_entry:
 	/* Leave keypress in buffer and start iPXE.  The keypress will
 	 * cause the usual initial Ctrl-B prompt to be skipped.
 	 */
-	xorl	%ebp, %ebp	/* Allow relocation */
+	orl	$0xffffffff, %ebp	/* Allow arbitrary relocation */
 	pushw	%cs
 	call	exec
 1:	/* Try to call original INT 19 vector */
diff --git a/src/arch/i386/prefix/undiloader.S b/src/arch/i386/prefix/undiloader.S
index bb3d469b..ccdd816e 100644
--- a/src/arch/i386/prefix/undiloader.S
+++ b/src/arch/i386/prefix/undiloader.S
@@ -31,7 +31,7 @@ undiloader:
 	movw	%es:14(%di), %ax
 	movl	image_source, %esi
 	movl	decompress_to, %edi
-	xorl	%ebp, %ebp		/* Allow relocation */
+	orl	$0xffffffff, %ebp	/* Allow arbitrary relocation */
 	call	install_prealloc
 	popw	%di
 	/* Call UNDI loader C code */