diff -ru usr/src/nv/os-agp.c usr/src/nv.1233959/os-agp.c
--- usr/src/nv/os-agp.c	2005-02-25 18:37:02.000000000 +0100
+++ usr/src/nv.1233959/os-agp.c	2005-03-07 20:57:17.235559352 +0100
@@ -176,7 +176,7 @@
     rm_read_registry_dword(NULL, "NVreg", "EnableAGPFW", &enable_fw);
     agp_mode |= NV_AGPGART_MODE_BITS_SBA(enable_fw);
 
-    agp_info.mode &= agp_mode;
+    agp_info.mode &= (0xff000000 | agp_mode);
     NV_AGPGART_BACKEND_ENABLE(drm_agp_p, nvl->agp_bridge, agp_info.mode);