diff --git a/src/radeon_driver.c b/src/radeon_driver.c
index 7424577..3ddb2c2 100644
--- a/src/radeon_driver.c
+++ b/src/radeon_driver.c
@@ -1271,8 +1271,10 @@ static void RADEONInitMemoryMap(ScrnInfoPtr pScrn)
      * but the real video RAM instead
      */
     if (info->ChipFamily >= CHIP_FAMILY_R600) {
-	mem_size = INREG(R600_CONFIG_MEMSIZE);
-	aper_size = INREG(R600_CONFIG_APER_SIZE);
+	//mem_size = INREG(R600_CONFIG_MEMSIZE);
+	mem_size = (((info->mc_fb_location & 0xffff0000) - ((info->mc_fb_location & 0xffff) << 16))) << 8;
+	//aper_size = INREG(R600_CONFIG_APER_SIZE);
+	aper_size = mem_size;
     } else {
 	mem_size = INREG(RADEON_CONFIG_MEMSIZE);
 	aper_size = INREG(RADEON_CONFIG_APER_SIZE);
@@ -1333,8 +1335,8 @@ static void RADEONInitMemoryMap(ScrnInfoPtr pScrn)
 		    aper0_base &= ~(mem_size - 1);
 
 	    if (info->ChipFamily >= CHIP_FAMILY_R600) {
-		info->mc_fb_location = (aper0_base >> 24) |
-		    (((aper0_base + mem_size - 1) & 0xff000000U) >> 8);
+		info->mc_fb_location = ((aper0_base >> 24) & 0x0000ffff) |
+		    (((aper0_base + mem_size) >> 8) & 0xffff0000);
 		ErrorF("mc fb loc is %08x\n", (unsigned int)info->mc_fb_location);
 	    } else {
 		info->mc_fb_location = (aper0_base >> 16) |