--- xc/programs/Xserver/hw/xfree86/drivers/tdfx/tdfx_driver.c.tdfx-enable-interlaced-modes	Sun Feb  3 07:28:12 2002
+++ xc/programs/Xserver/hw/xfree86/drivers/tdfx/tdfx_driver.c	Sun Feb  3 08:38:10 2002
@@ -960,7 +960,18 @@
   clockRanges->minClock= 12000; /* !!! What's the min clock? !!! */
   clockRanges->maxClock=pTDFX->MaxClock;
   clockRanges->clockIndex = -1;
-  clockRanges->interlaceAllowed = FALSE;
+  switch (pTDFX->ChipType) {
+    case PCI_CHIP_BANSHEE:
+      clockRanges->interlaceAllowed = FALSE;
+      break;
+    case PCI_CHIP_VOODOO3:
+    case PCI_CHIP_VOODOO5:
+      clockRanges->interlaceAllowed = TRUE;
+      break;
+    default:
+      clockRanges->interlaceAllowed = FALSE;
+      break;
+  }    
   clockRanges->doubleScanAllowed = TRUE;
 
   /*
@@ -1836,7 +1847,6 @@
 {
   int heightInTiles;            /* Height of buffer in tiles */
 
-
   /* Calculate tile height stuff */
   heightInTiles = yres >> 5;
   
@@ -2394,9 +2404,21 @@
   TDFXTRACE("TDFXValidMode start\n");
   if ((mode->HDisplay>2048) || (mode->VDisplay>1536)) 
     return MODE_BAD;
-  /* Banshee doesn't support interlace. Does V3? */
-  if (mode->Flags&V_INTERLACE) 
-    return MODE_BAD;
+  /* Banshee doesn't support interlace, but Voodoo 3 and higher do. */
+  if (mode->Flags&V_INTERLACE) {
+    switch (pTDFX->ChipType) {
+      case PCI_CHIP_BANSHEE:
+        return MODE_BAD;
+        break;
+      case PCI_CHIP_VOODOO3:
+      case PCI_CHIP_VOODOO5:
+        return MODE_GOOD;
+        break;
+      default:
+        return MODE_BAD;
+        break;
+    }
+  }
   /* In clock doubled mode widths must be divisible by 16 instead of 8 */
   if ((mode->Clock>TDFX2XCUTOFF) && (mode->HDisplay%16))
     return MODE_BAD;