diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index e74a9d5a51..8281f409f2 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -32,7 +32,6 @@
   DEFINE SMM_REQUIRE             = FALSE
   DEFINE TPM2_ENABLE             = FALSE
   DEFINE TPM2_CONFIG_ENABLE      = FALSE
-  DEFINE USE_LEGACY_ISA_STACK    = FALSE
 
   #
   # Network definition
@@ -748,16 +747,9 @@
   #
   # ISA Support
   #
-!if $(USE_LEGACY_ISA_STACK) == FALSE
   OvmfPkg/SioBusDxe/SioBusDxe.inf
   MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
   MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
-!else
-  PcAtChipsetPkg/IsaAcpiDxe/IsaAcpi.inf
-  IntelFrameworkModulePkg/Bus/Isa/IsaBusDxe/IsaBusDxe.inf
-  IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/IsaSerialDxe.inf
-  IntelFrameworkModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2keyboardDxe.inf
-!endif
 
   #
   # SMBIOS Support
diff --git a/OvmfPkg/OvmfPkgIa32.fdf b/OvmfPkg/OvmfPkgIa32.fdf
index e428334702..12da9f4706 100644
--- a/OvmfPkg/OvmfPkgIa32.fdf
+++ b/OvmfPkg/OvmfPkgIa32.fdf
@@ -259,20 +259,11 @@ INF  MdeModulePkg/Universal/SetupBrowserDxe/SetupBrowserDxe.inf
 INF  MdeModulePkg/Universal/DisplayEngineDxe/DisplayEngineDxe.inf
 INF  MdeModulePkg/Universal/MemoryTest/NullMemoryTestDxe/NullMemoryTestDxe.inf
 
-!if $(USE_LEGACY_ISA_STACK) == FALSE
-  INF  OvmfPkg/SioBusDxe/SioBusDxe.inf
+INF  OvmfPkg/SioBusDxe/SioBusDxe.inf
 !ifndef $(SOURCE_DEBUG_ENABLE)
-  INF  MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
-!endif
-  INF  MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
-!else
-  INF  PcAtChipsetPkg/IsaAcpiDxe/IsaAcpi.inf
-  INF  IntelFrameworkModulePkg/Bus/Isa/IsaBusDxe/IsaBusDxe.inf
-!ifndef $(SOURCE_DEBUG_ENABLE)
-  INF  IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/IsaSerialDxe.inf
-!endif
-  INF  IntelFrameworkModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2keyboardDxe.inf
+INF  MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
 !endif
+INF  MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
 
 INF  MdeModulePkg/Universal/SmbiosDxe/SmbiosDxe.inf
 INF  OvmfPkg/SmbiosPlatformDxe/SmbiosPlatformDxe.inf
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 67ac015991..30d094d217 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -32,7 +32,6 @@
   DEFINE SMM_REQUIRE             = FALSE
   DEFINE TPM2_ENABLE             = FALSE
   DEFINE TPM2_CONFIG_ENABLE      = FALSE
-  DEFINE USE_LEGACY_ISA_STACK    = FALSE
 
   #
   # Network definition
@@ -757,16 +756,9 @@
   #
   # ISA Support
   #
-!if $(USE_LEGACY_ISA_STACK) == FALSE
   OvmfPkg/SioBusDxe/SioBusDxe.inf
   MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
   MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
-!else
-  PcAtChipsetPkg/IsaAcpiDxe/IsaAcpi.inf
-  IntelFrameworkModulePkg/Bus/Isa/IsaBusDxe/IsaBusDxe.inf
-  IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/IsaSerialDxe.inf
-  IntelFrameworkModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2keyboardDxe.inf
-!endif
 
   #
   # SMBIOS Support
diff --git a/OvmfPkg/OvmfPkgIa32X64.fdf b/OvmfPkg/OvmfPkgIa32X64.fdf
index 6ddffe7547..47ac7d8646 100644
--- a/OvmfPkg/OvmfPkgIa32X64.fdf
+++ b/OvmfPkg/OvmfPkgIa32X64.fdf
@@ -260,20 +260,11 @@ INF  MdeModulePkg/Universal/SetupBrowserDxe/SetupBrowserDxe.inf
 INF  MdeModulePkg/Universal/DisplayEngineDxe/DisplayEngineDxe.inf
 INF  MdeModulePkg/Universal/MemoryTest/NullMemoryTestDxe/NullMemoryTestDxe.inf
 
-!if $(USE_LEGACY_ISA_STACK) == FALSE
-  INF  OvmfPkg/SioBusDxe/SioBusDxe.inf
+INF  OvmfPkg/SioBusDxe/SioBusDxe.inf
 !ifndef $(SOURCE_DEBUG_ENABLE)
-  INF  MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
-!endif
-  INF  MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
-!else
-  INF  PcAtChipsetPkg/IsaAcpiDxe/IsaAcpi.inf
-  INF  IntelFrameworkModulePkg/Bus/Isa/IsaBusDxe/IsaBusDxe.inf
-!ifndef $(SOURCE_DEBUG_ENABLE)
-  INF  IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/IsaSerialDxe.inf
-!endif
-  INF  IntelFrameworkModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2keyboardDxe.inf
+INF  MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
 !endif
+INF  MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
 
 INF  MdeModulePkg/Universal/SmbiosDxe/SmbiosDxe.inf
 INF  OvmfPkg/SmbiosPlatformDxe/SmbiosPlatformDxe.inf
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 68073ef55b..705795f0da 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -32,7 +32,6 @@
   DEFINE SMM_REQUIRE             = FALSE
   DEFINE TPM2_ENABLE             = FALSE
   DEFINE TPM2_CONFIG_ENABLE      = FALSE
-  DEFINE USE_LEGACY_ISA_STACK    = FALSE
 
   #
   # Network definition
@@ -755,16 +754,9 @@
   #
   # ISA Support
   #
-!if $(USE_LEGACY_ISA_STACK) == FALSE
   OvmfPkg/SioBusDxe/SioBusDxe.inf
   MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
   MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
-!else
-  PcAtChipsetPkg/IsaAcpiDxe/IsaAcpi.inf
-  IntelFrameworkModulePkg/Bus/Isa/IsaBusDxe/IsaBusDxe.inf
-  IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/IsaSerialDxe.inf
-  IntelFrameworkModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2keyboardDxe.inf
-!endif
 
   #
   # SMBIOS Support
diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf
index 6ddffe7547..47ac7d8646 100644
--- a/OvmfPkg/OvmfPkgX64.fdf
+++ b/OvmfPkg/OvmfPkgX64.fdf
@@ -260,20 +260,11 @@ INF  MdeModulePkg/Universal/SetupBrowserDxe/SetupBrowserDxe.inf
 INF  MdeModulePkg/Universal/DisplayEngineDxe/DisplayEngineDxe.inf
 INF  MdeModulePkg/Universal/MemoryTest/NullMemoryTestDxe/NullMemoryTestDxe.inf
 
-!if $(USE_LEGACY_ISA_STACK) == FALSE
-  INF  OvmfPkg/SioBusDxe/SioBusDxe.inf
+INF  OvmfPkg/SioBusDxe/SioBusDxe.inf
 !ifndef $(SOURCE_DEBUG_ENABLE)
-  INF  MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
-!endif
-  INF  MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
-!else
-  INF  PcAtChipsetPkg/IsaAcpiDxe/IsaAcpi.inf
-  INF  IntelFrameworkModulePkg/Bus/Isa/IsaBusDxe/IsaBusDxe.inf
-!ifndef $(SOURCE_DEBUG_ENABLE)
-  INF  IntelFrameworkModulePkg/Bus/Isa/IsaSerialDxe/IsaSerialDxe.inf
-!endif
-  INF  IntelFrameworkModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2keyboardDxe.inf
+INF  MdeModulePkg/Bus/Pci/PciSioSerialDxe/PciSioSerialDxe.inf
 !endif
+INF  MdeModulePkg/Bus/Isa/Ps2KeyboardDxe/Ps2KeyboardDxe.inf
 
 INF  MdeModulePkg/Universal/SmbiosDxe/SmbiosDxe.inf
 INF  OvmfPkg/SmbiosPlatformDxe/SmbiosPlatformDxe.inf