Index: src/radeon_driver.c
===================================================================
RCS file: /cvs/xorg/driver/xf86-video-ati/src/radeon_driver.c,v
retrieving revision 1.85
diff -p -u -r1.85 radeon_driver.c
--- src/radeon_driver.c	19 Jan 2006 14:20:37 -0000	1.85
+++ src/radeon_driver.c	16 Feb 2006 18:30:29 -0000
@@ -1721,6 +1721,15 @@ static void RADEONGetClockInfo(ScrnInfoP
         info->mclk = 200.00;
     }
 
+    if (info->ChipFamily == CHIP_FAMILY_RV100 && !info->HasCRTC2) {
+        /* Avoid RN50 corruption due to memory bandwidth starvation.
+         * 18 is an empirical value based on the databook and Windows driver.
+        */
+        pll->max_pll_freq = min(pll->max_pll_freq,
+                               18 * info->mclk * 100 / pScrn->bitsPerPixel *
+                               info->RamWidth / 16);
+    }
+
     xf86DrvMsg (pScrn->scrnIndex, X_INFO,
 		"PLL parameters: rf=%d rd=%d min=%ld max=%ld; xclk=%d\n",
 		pll->reference_freq,
@@ -2358,6 +2367,10 @@ static void RADEONGetVRamType(ScrnInfoPt
 	       (info->ChipFamily == CHIP_FAMILY_RS200)){
 	if (tmp & RV100_HALF_MODE) info->RamWidth = 32;
 	else info->RamWidth = 64;
+       if (!info->HasCRTC2) {
+           info->RamWidth /= 4;
+           info->IsDDR = TRUE;
+       }
     } else {
 	if (tmp & RADEON_MEM_NUM_CHANNELS_MASK) info->RamWidth = 128;
 	else info->RamWidth = 64;
@@ -2424,10 +2437,11 @@ static Bool RADEONPreInitConfig(ScrnInfo
 	info->ChipFamily = CHIP_FAMILY_RV100;
 	break;
 
-    case PCI_CHIP_RV100_QY:
-    case PCI_CHIP_RV100_QZ:
     case PCI_CHIP_RN50_515E:  /* RN50 is based on the RV100 but 3D isn't guaranteed to work.  YMMV. */
     case PCI_CHIP_RN50_5969:
+        info->HasCRTC2 = FALSE;
+    case PCI_CHIP_RV100_QY:
+    case PCI_CHIP_RV100_QZ:
 	info->ChipFamily = CHIP_FAMILY_RV100;
 
 	/* DELL triple-head configuration. */