diff --git a/usr.sbin/acpi/acpidump/acpi.c b/usr.sbin/acpi/acpidump/acpi.c
index 971e0211612a..e22aad410656 100644
--- a/usr.sbin/acpi/acpidump/acpi.c
+++ b/usr.sbin/acpi/acpidump/acpi.c
@@ -716,8 +716,41 @@ sdt_load_devmem(void)
 	return (rsdp);
 }
 
+static int
+write_dsdt(int fd, struct ACPIsdt *rsdt, struct ACPIsdt *dsdt)
+{
+	struct ACPIsdt sdt;
+	struct ACPIsdt *ssdt;
+	uint8_t sum;
+
+	sdt = *dsdt;
+	if (rsdt != NULL) {
+		sdt.check = 0;
+		sum = acpi_checksum(dsdt->body, dsdt->len - SIZEOF_SDT_HDR);
+		ssdt = sdt_from_rsdt(rsdt, "SSDT", NULL);
+		while (ssdt != NULL) {
+			sdt.len += ssdt->len - SIZEOF_SDT_HDR;
+			sum += acpi_checksum(ssdt->body,
+			    ssdt->len - SIZEOF_SDT_HDR);
+			ssdt = sdt_from_rsdt(rsdt, "SSDT", ssdt);
+		}
+		sum += acpi_checksum(&sdt, SIZEOF_SDT_HDR);
+		sdt.check -= sum;
+	}
+	write(fd, &sdt, SIZEOF_SDT_HDR);
+	write(fd, dsdt->body, dsdt->len - SIZEOF_SDT_HDR);
+	if (rsdt != NULL) {
+		ssdt = sdt_from_rsdt(rsdt, "SSDT", NULL);
+		while (ssdt != NULL) {
+			write(fd, ssdt->body, ssdt->len - SIZEOF_SDT_HDR);
+			ssdt = sdt_from_rsdt(rsdt, "SSDT", ssdt);
+		}
+	}
+	return (0);
+}
+
 void
-dsdt_save_file(char *outfile, struct ACPIsdt *dsdp)
+dsdt_save_file(char *outfile, struct ACPIsdt *rsdt, struct ACPIsdt *dsdp)
 {
 	int	fd;
 	mode_t	mode;
@@ -729,13 +762,12 @@ dsdt_save_file(char *outfile, struct ACPIsdt *dsdp)
 		perror("dsdt_save_file");
 		return;
 	}
-	write(fd, dsdp, SIZEOF_SDT_HDR);
-	write(fd, dsdp->body, dsdp->len - SIZEOF_SDT_HDR);
+	write_dsdt(fd, rsdt, dsdp);
 	close(fd);
 }
 
 void
-aml_disassemble(struct ACPIsdt *dsdp)
+aml_disassemble(struct ACPIsdt *rsdt, struct ACPIsdt *dsdp)
 {
 	char tmpstr[32], buf[256];
 	FILE *fp;
@@ -747,10 +779,7 @@ aml_disassemble(struct ACPIsdt *dsdp)
 		perror("iasl tmp file");
 		return;
 	}
-
-	/* Dump DSDT to the temp file */
-	write(fd, dsdp, SIZEOF_SDT_HDR);
-	write(fd, dsdp->body, dsdp->len - SIZEOF_SDT_HDR);
+	write_dsdt(fd, rsdt, dsdp);
 	close(fd);
 
 	/* Run iasl -d on the temp file */
@@ -783,9 +812,9 @@ sdt_print_all(struct ACPIsdt *rsdp)
 	acpi_handle_rsdt(rsdp);
 }
 
-/* Fetch a table matching the given signature via the RSDT */
+/* Fetch a table matching the given signature via the RSDT. */
 struct ACPIsdt *
-sdt_from_rsdt(struct ACPIsdt *rsdt, const char *sig)
+sdt_from_rsdt(struct ACPIsdt *rsdt, const char *sig, struct ACPIsdt *last)
 {
 	struct ACPIsdt *sdt;
 	vm_offset_t addr;
@@ -804,6 +833,11 @@ sdt_from_rsdt(struct ACPIsdt *rsdt, const char *sig)
 			assert((addr = 0));
 		}
 		sdt = (struct ACPIsdt *)acpi_map_sdt(addr);
+		if (last != NULL) {
+			if (sdt == last)
+				last = NULL;
+			continue;
+		}
 		if (memcmp(sdt->signature, sig, strlen(sig)))
 			continue;
 		if (acpi_checksum(sdt, sdt->len))
diff --git a/usr.sbin/acpi/acpidump/acpidump.c b/usr.sbin/acpi/acpidump/acpidump.c
index 269a595cbd43..b9b8b0a081e1 100644
--- a/usr.sbin/acpi/acpidump/acpidump.c
+++ b/usr.sbin/acpi/acpidump/acpidump.c
@@ -54,7 +54,7 @@ main(int argc, char *argv[])
 {
 	char	c, *progname;
 	char	*dsdt_input_file, *dsdt_output_file;
-	struct	ACPIsdt *sdt;
+	struct	ACPIsdt *rsdt, *sdt;
 
 	dsdt_input_file = dsdt_output_file = NULL;
 	progname = argv[0];
@@ -99,38 +99,41 @@ main(int argc, char *argv[])
 		}
 		if (vflag)
 			warnx("loading DSDT file: %s", dsdt_input_file);
-		sdt = dsdt_load_file(dsdt_input_file);
+		rsdt = dsdt_load_file(dsdt_input_file);
 	} else {
 		if (vflag)
 			warnx("loading RSD PTR from /dev/mem");
-		sdt = sdt_load_devmem();
+		rsdt = sdt_load_devmem();
 	}
 
 	/* Display misc. SDT tables (only available when using /dev/mem) */
 	if (tflag) {
 		if (vflag)
 			warnx("printing various SDT tables");
-		sdt_print_all(sdt);
+		sdt_print_all(rsdt);
 	}
 
 	/* Translate RSDT to DSDT pointer */
 	if (dsdt_input_file == NULL) {
-		sdt = sdt_from_rsdt(sdt, "FACP");
+		sdt = sdt_from_rsdt(rsdt, "FACP", NULL);
 		sdt = dsdt_from_fadt((struct FADTbody *)sdt->body);
+	} else {
+		sdt = rsdt;
+		rsdt = NULL;
 	}
 
 	/* Dump the DSDT to a file */
 	if (dsdt_output_file != NULL) {
 		if (vflag)
 			warnx("saving DSDT file: %s", dsdt_output_file);
-		dsdt_save_file(dsdt_output_file, sdt);
+		dsdt_save_file(dsdt_output_file, rsdt, sdt);
 	}
 
 	/* Disassemble the DSDT into ASL */
 	if (dflag) {
 		if (vflag)
 			warnx("disassembling DSDT, iasl messages follow");
-		aml_disassemble(sdt);
+		aml_disassemble(rsdt, sdt);
 		if (vflag)
 			warnx("iasl processing complete");
 	}
diff --git a/usr.sbin/acpi/acpidump/acpidump.h b/usr.sbin/acpi/acpidump/acpidump.h
index 1ebc56d8e006..ca56398af2a9 100644
--- a/usr.sbin/acpi/acpidump/acpidump.h
+++ b/usr.sbin/acpi/acpidump/acpidump.h
@@ -314,18 +314,19 @@ struct ACPIsdt  *sdt_load_devmem(void);
 struct ACPIsdt  *dsdt_load_file(char *);
 
 /* Save the DSDT to a file */
-void		 dsdt_save_file(char *, struct ACPIsdt *);
+void		 dsdt_save_file(char *, struct ACPIsdt *, struct ACPIsdt *);
 
 /* Print out as many fixed tables as possible, given the RSD PTR */
 void		 sdt_print_all(struct ACPIsdt *);
 
 /* Disassemble the AML in the DSDT */
-void		 aml_disassemble(struct ACPIsdt *);
+void		 aml_disassemble(struct ACPIsdt *, struct ACPIsdt *);
 
 /* Routines for accessing tables in physical memory */
 struct ACPIrsdp	*acpi_find_rsd_ptr(void);
 void		*acpi_map_physical(vm_offset_t, size_t);
-struct ACPIsdt	*sdt_from_rsdt(struct ACPIsdt *, const char *);
+struct ACPIsdt	*sdt_from_rsdt(struct ACPIsdt *, const char *,
+    struct ACPIsdt *);
 struct ACPIsdt	*dsdt_from_fadt(struct FADTbody *);
 int		 acpi_checksum(void *, size_t);