diff --git a/src/via_display.c b/src/via_display.c
index 18e85f7..ec68d05 100644
--- a/src/via_display.c
+++ b/src/via_display.c
@@ -2113,10 +2113,10 @@ viaIGA2SetDisplayRegister(ScrnInfoPtr pScrn, DisplayModePtr mode)
 
 
     /* Set IGA2 horizontal display end position. */
-    /* Horizontal Active Data Period: 2048 - 1 (max) */
+    /* Horizontal Active Data Period: 2048 - 2 (max) */
     DEBUG(xf86DrvMsg(pScrn->scrnIndex, X_INFO,
                         "IGA2 CrtcHDisplay: %d\n", mode->CrtcHDisplay));
-    temp = mode->CrtcHDisplay - 1;
+    temp = mode->CrtcHDisplay - 2;
 
     /* 3X5.51[7:0] - Horizontal Active Data Period Bits [7:0] */
     hwp->writeCrtc(hwp, 0x51, temp & 0xFF);
@@ -2206,10 +2206,10 @@ viaIGA2SetDisplayRegister(ScrnInfoPtr pScrn, DisplayModePtr mode)
 
 
     /* Set IGA2 vertical display end position. */
-    /* Vertical Active Data Period: 2048 - 1 (max) */
+    /* Vertical Active Data Period: 2048 - 2 (max) */
     DEBUG(xf86DrvMsg(pScrn->scrnIndex, X_INFO,
                         "IGA2 CrtcVDisplay: %d\n", mode->CrtcVDisplay));
-    temp = mode->CrtcVDisplay - 1;
+    temp = mode->CrtcVDisplay - 2;
 
     /* 3X5.59[7:0] - Vertical Active Data Period Bits [7:0] */
     hwp->writeCrtc(hwp, 0x59, temp & 0xFF);