diff --git a/usr.sbin/acpi/acpidump/acpi_user.c b/usr.sbin/acpi/acpidump/acpi_user.c
index 2166e884c800..550420c677ea 100644
--- a/usr.sbin/acpi/acpidump/acpi_user.c
+++ b/usr.sbin/acpi/acpidump/acpi_user.c
@@ -142,7 +142,9 @@ acpi_scan_rsd_ptr(void)
 	for (; addr < end; addr += 16)
 		if ((rsdp = acpi_get_rsdp(addr)) != NULL)
 			return (rsdp);
-	for (addr = RSDP_HI_START; addr < RSDP_HI_END; addr += 16)
+	addr = RSDP_HI_START;
+	end = addr + RSDP_HI_SIZE;
+	for (; addr < end; addr += 16)
 		if ((rsdp = acpi_get_rsdp(addr)) != NULL)
 			return (rsdp);
 #endif /* __i386__ */
diff --git a/usr.sbin/acpi/acpidump/acpidump.h b/usr.sbin/acpi/acpidump/acpidump.h
index 6cd7a8e7b18a..1ebc56d8e006 100644
--- a/usr.sbin/acpi/acpidump/acpidump.h
+++ b/usr.sbin/acpi/acpidump/acpidump.h
@@ -296,13 +296,13 @@ struct ECDTbody {
 /*
  * Addresses to scan on ia32 for the RSD PTR.  According to section 5.2.2
  * of the ACPI spec, we only consider two regions for the base address:
- * 1. EBDA (0x0 - 0x3FF)
+ * 1. EBDA (1 KB area addressed to by 16 bit pointer at 0x40E)
  * 2. High memory (0xE0000 - 0xFFFFF)
  */
 #define RSDP_EBDA_PTR	0x40E
-#define RSDP_EBDA_SIZE	(1024 - sizeof(struct ACPIrsdp))
+#define RSDP_EBDA_SIZE	0x400
 #define RSDP_HI_START	0xE0000
-#define RSDP_HI_END	(0x100000 - sizeof(struct ACPIrsdp))
+#define RSDP_HI_SIZE	0x20000
 
 /* Find and map the RSD PTR structure and return it for parsing */
 struct ACPIsdt  *sdt_load_devmem(void);