diff --git a/src/northbridge/intel/i440bx/acpi/sb_pci0_crs.asl b/src/northbridge/intel/i440bx/acpi/sb_pci0_crs.asl
index fe66f39..ce71aed 100644
--- a/src/northbridge/intel/i440bx/acpi/sb_pci0_crs.asl
+++ b/src/northbridge/intel/i440bx/acpi/sb_pci0_crs.asl
@@ -1,21 +1,19 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-/* i440bx Northbridge */
+/* i440bx Northbridge resources that sits on \_SB.PCI0 */
 Device (NB)
 {
 	Name(_ADR, 0x00000000)
 	OperationRegion(PCIC, PCI_Config, 0x00, 0x100)
-}
-
-Field (NB.PCIC, AnyAcc, NoLock, Preserve)
-{
-	Offset (0x67),	// DRB7
-	DRB7,	8,
-}
-
-Method(TOM1, 0) {
-	/* Multiply by 8MB to get TOM */
-	Return(ShiftLeft(DRB7, 23))
+	Field (PCIC, ByteAcc, NoLock, Preserve)
+	{
+		Offset (0x67),	// DRB7
+		DRB7,	8,
+	}
+	Method(TOM1, 0) {
+		/* Multiply by 8MB to get TOM */
+		Return(DRB7 << 23)
+	}
 }
 
 Method(_CRS, 0) {
@@ -60,10 +58,9 @@
 	 * 32bit (0x00000000 - TOM1) will wrap and give the same
 	 * result as 64bit (0x100000000 - TOM1).
 	 */
-	Store(TOM1, MM1B)
-	ShiftLeft(0x10000000, 4, Local0)
-	Subtract(Local0, TOM1, Local0)
-	Store(Local0, MM1L)
+	MM1B = \_SB.PCI0.NB.TOM1
+	Local0 = 0x10000000 << 4
+	MM1L = Local0 - MM1B
 
 	Return(TMP)
 }