Index: xf86-video-ati-6.13.0/src/radeon_driver.c
===================================================================
--- xf86-video-ati-6.13.0.orig/src/radeon_driver.c
+++ xf86-video-ati-6.13.0/src/radeon_driver.c
@@ -3221,6 +3221,21 @@ Bool RADEONPreInit(ScrnInfoPtr pScrn, in
     if (!RADEONPreInitControllers(pScrn))
        goto fail;
 
+    /* Unless we're able to shrink/enlarge FB on the fly (GEM etc.), allocate
+     * large enough (TM) virtual size */
+    if (!pScrn->display->virtualX || !pScrn->display->virtualY) {
+	/* Have at least enough space for double buffering and z Buffer + some textures */
+	if (2 * 1920*1920 * (pScrn->bitsPerPixel/8) <= pScrn->videoRam / 4 * 1024) {
+	    /* Fits on 128MB and up */
+	    pScrn->display->virtualX = 2 * 1920;
+	    pScrn->display->virtualY = 1920;
+	} else if (2 * 1680*1280 * (pScrn->bitsPerPixel/8) <= pScrn->videoRam / 4 * 1024) {
+	    /* Fits on 64MB and up */
+	    pScrn->display->virtualX = 2 * 1680;
+	    pScrn->display->virtualY = 1280;
+	}
+    }
+
     if (!xf86InitialConfiguration (pScrn, FALSE))
    {
       xf86DrvMsg(pScrn->scrnIndex, X_ERROR, "No valid modes.\n");