diff --git a/src/soc/amd/picasso/acpi/sb_pci0_fch.asl b/src/soc/amd/picasso/acpi/sb_pci0_fch.asl
index cbb1b91782..ed321f3e32 100644
--- a/src/soc/amd/picasso/acpi/sb_pci0_fch.asl
+++ b/src/soc/amd/picasso/acpi/sb_pci0_fch.asl
@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <arch/ioapic.h>
+
 External(\_SB.ALIB, MethodObj)
 
 /* System Bus */
@@ -71,16 +73,9 @@ Method(_CRS, 0) {
 	CreateDWordField(CRES, ^MMIO._BAS, MM1B)
 	CreateDWordField(CRES, ^MMIO._LEN, MM1L)
 
-	/*
-	 * Declare memory between TOM1 and 4GB as available
-	 * for PCI MMIO.
-	 * Use ShiftLeft to avoid 64bit constant (for XP).
-	 * This will work even if the OS does 32bit arithmetic, as
-	 * 32bit (0x00000000 - TOM1) will wrap and give the same
-	 * result as 64bit (0x100000000 - TOM1).
-	 */
+	/* Declare memory between TOM1 and IOAPIC as available for PCI MMIO. */
 	MM1B = TOM1
-	Local0 = 0x10000000 << 4
+	Local0 = IO_APIC_ADDR /* This is the first MMIO device after TOM1. */
 	Local0 -= TOM1
 	MM1L = Local0