diff --git a/src/i830_display.c b/src/i830_display.c
index 6fe7be7..83ae08d 100644
--- a/src/i830_display.c
+++ b/src/i830_display.c
@@ -35,6 +35,7 @@
 #include <assert.h>
 #include <stdlib.h>
 #include <math.h>
+#include <signal.h>
 
 #include "xf86.h"
 #include "i830.h"
@@ -498,6 +499,51 @@ i830_pipe_a_require_deactivate (ScrnInfoPtr scrn)
     return;
 }
 
+#define FBC_TAG0 0x3300
+#define FBC_NUM_TAGS 49
+#define FBC_TAG_MODIFIED 0
+#define FBC_TAG_UNCOMPRESSED 1
+#define FBC_TAG_UNCOMPRESSIBLE 2
+#define FBC_TAG_COMPRESSED 3
+static void i830_fbc_dump_tags(void)
+{
+    ScrnInfoPtr pScrn = xf86Screens[0];
+    I830Ptr pI830 = I830PTR(pScrn);
+    uint32_t tag[FBC_NUM_TAGS];
+    int modified = 0, uncompressed = 0, uncompressible = 0, compressed = 0;
+    int i, j;
+
+    for (i = 0; i < FBC_NUM_TAGS; i++) {
+	tag[i] = INREG(FBC_TAG0 + i);
+	for (j = 0; j < 32; j += 2) {
+	    uint32_t val = (tag[i] >> j) & 3;
+	    /* Each value corresponds to a status for two lines */
+	    if (val == FBC_TAG_MODIFIED)
+		modified += 2;
+	    else if (val == FBC_TAG_UNCOMPRESSED)
+		uncompressed += 2;
+	    else if (val == FBC_TAG_UNCOMPRESSIBLE)
+		uncompressible += 2;
+	    else if (val == FBC_TAG_COMPRESSED)
+		compressed += 2;
+	}
+    }
+
+    ErrorF("FBC_CONTROL: 0x%08x\n", INREG(FBC_CONTROL));
+    ErrorF("FBC_STATUS: 0x%08x\n", INREG(FBC_STATUS));
+    ErrorF("FBC TAG status:\n");
+    ErrorF("\tmodified: %d\n", modified);
+    ErrorF("\tuncompressed: %d\n", uncompressed);
+    ErrorF("\tuncompressible: %d\n", uncompressible);
+    ErrorF("\tcompressed: %d\n", compressed);
+}
+
+static void fbc_debug(int signo)
+{
+    i830_fbc_dump_tags();
+    alarm(5);
+}
+
 static Bool
 i830_use_fb_compression(xf86CrtcPtr crtc)
 {
@@ -595,6 +641,11 @@ i830_enable_fb_compression(xf86CrtcPtr crtc)
 
     xf86DrvMsg(pScrn->scrnIndex, X_INFO, "fbc enabled on plane %c\n", pipe ?
 	       'b' : 'a');
+    {
+	struct sigaction debug = { .sa_handler = fbc_debug };
+	sigaction(SIGALRM, &debug, NULL);
+	alarm(5);
+    }
 }
 
 static void