diff --git a/sys/src/9/pc/vgaigfx.c b/sys/src/9/pc/vgaigfx.c
index 30b2096e8..9b03c9bbb 100644
--- a/sys/src/9/pc/vgaigfx.c
+++ b/sys/src/9/pc/vgaigfx.c
@@ -13,44 +13,67 @@
 #include "screen.h"
 
 static ulong
-preallocsize(Pcidev *p)
+stolenmb(Pcidev *p)
 {
 	switch(p->did){
 	case 0x0166:	/* Ivy Bridge */
 		switch((pcicfgr16(p, 0x50) >> 3) & 0x1f){
-		case 0x01:	return 32*MB	- 2*MB;
-		case 0x02:	return 64*MB	- 2*MB;
-		case 0x03:	return 96*MB	- 2*MB;
-		case 0x04:	return 128*MB	- 2*MB;
-		case 0x05:	return 32*MB	- 2*MB;
-		case 0x06:	return 48*MB	- 2*MB;
-		case 0x07:	return 64*MB	- 2*MB;
-		case 0x08:	return 128*MB	- 2*MB;
-		case 0x09:	return 256*MB	- 2*MB;
-		case 0x0A:	return 96*MB	- 2*MB;
-		case 0x0B:	return 160*MB	- 2*MB;
-		case 0x0C:	return 224*MB	- 2*MB;
-		case 0x0D:	return 352*MB	- 2*MB;
-		case 0x0E:	return 448*MB	- 2*MB;
-		case 0x0F:	return 480*MB	- 2*MB;
-		case 0x10:	return 512*MB	- 2*MB;
+		case 0x01:	return 32  - 2;
+		case 0x02:	return 64  - 2;
+		case 0x03:	return 96  - 2;
+		case 0x04:	return 128 - 2;
+		case 0x05:	return 32  - 2;
+		case 0x06:	return 48  - 2;
+		case 0x07:	return 64  - 2;
+		case 0x08:	return 128 - 2;
+		case 0x09:	return 256 - 2;
+		case 0x0A:	return 96  - 2;
+		case 0x0B:	return 160 - 2;
+		case 0x0C:	return 224 - 2;
+		case 0x0D:	return 352 - 2;
+		case 0x0E:	return 448 - 2;
+		case 0x0F:	return 480 - 2;
+		case 0x10:	return 512 - 2;
 		}
 		break;
 	case 0x2a42:	/* X200 */
+	case 0x2a02:	/* CF-R7 */
 		switch((pcicfgr16(p, 0x52) >> 4) & 7){
-		case 0x01:	return 1*MB;
-		case 0x02:	return 4*MB;
-		case 0x03:	return 8*MB;
-		case 0x04:	return 16*MB;
-		case 0x05:	return 32*MB;
-		case 0x06:	return 48*MB;
-		case 0x07:	return 64*MB;
+		case 0x01:	return 1;
+		case 0x02:	return 4;
+		case 0x03:	return 8;
+		case 0x04:	return 16;
+		case 0x05:	return 32;
+		case 0x06:	return 48;
+		case 0x07:	return 64;
 		}
 		break;
 	}
 	return 0;
 }
 
+static uintptr
+gmsize(Pcidev *pci, void *mmio)
+{
+	u32int x, i, npg, *gtt;
+
+	npg = stolenmb(pci)<<(20-12);
+	if(npg == 0)
+		return 0;
+	gtt = (u32int*)((uchar*)mmio + pci->mem[0].size/2);
+	if((gtt[0]&1) == 0)
+		return 0;
+	x = (gtt[0]>>12)+1;
+	for(i=1; i<npg; i++){
+		if((gtt[i]&1) == 0 || (gtt[i]>>12) != x)
+			break;
+		x++;
+	}
+	if(0) print("igfx: graphics memory at %p-%p (%ud MB)\n", 
+		(uintptr)(x-i)<<12, (uintptr)x<<12, (i>>(20-12)));
+	return (uintptr)i<<12;
+}
+
 static void
 igfxenable(VGAscr* scr)
 {
@@ -69,8 +92,10 @@ igfxenable(VGAscr* scr)
 		vgalinearpci(scr);
 	if(scr->apsize){
 		addvgaseg("igfxscreen", scr->paddr, scr->apsize);
-		scr->storage = preallocsize(p);
-		if(scr->storage > scr->apsize)
+		scr->storage = gmsize(p, scr->mmio);
+		if(scr->storage < MB)
+			scr->storage = 0;
+		else if(scr->storage > scr->apsize)
 			scr->storage = scr->apsize;
 		if(scr->storage != 0)
 			scr->storage -= PGROUND(64*64*4);
@@ -133,6 +158,7 @@ igfxcurregs(VGAscr* scr, int pipe)
 			return nil;
 		break;
 	case 0x2a42:	/* X200 */
+	case 0x2a02:	/* CF-R7 */
 		if(pipe > 1)
 			return nil;
 		o = pipe*0x40;