diff --git a/src/northbridge/intel/gm45/ram_calc.c b/src/northbridge/intel/gm45/ram_calc.c
new file mode 100644
index 0000000..1da9e87
--- /dev/null
+++ b/src/northbridge/intel/gm45/ram_calc.c
@@ -0,0 +1,102 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2012 secunet Security Networks AG
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; version 2 of
+ * the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ */
+
+#include <stdint.h>
+#include <arch/io.h>
+#include <arch/romcc_io.h>
+#include <device/pci_def.h>
+#include <console/console.h>
+#include "gm45.h"
+
+/** Decodes used Graphics Mode Select (GMS) to kilobytes. */
+u32 decode_igd_memory_size(const u32 gms)
+{
+	switch (gms) {
+	case 1:
+		return   1 << 10;
+	case 2:
+		return   4 << 10; /* guessed */
+	case 3:
+		return   8 << 10; /* guessed */
+	case 4:
+		return  16 << 10;
+	case 5:
+		return  32 << 10;
+	case 7:
+		return  64 << 10;
+	case 8:
+		return 128 << 10;
+	case 9:
+		return 256 << 10;
+	case 10:
+		return  96 << 10;
+	case 11:
+		return 160 << 10;
+	case 12:
+		return 224 << 10;
+	case 13:
+		return 352 << 10;
+	default:
+		die("Bad Graphics Mode Select (GMS) setting.\n");
+		return 0;
+	}
+}
+
+/** Decodes used Graphics Stolen Memory (GSM) to kilobytes. */
+u32 decode_igd_gtt_size(const u32 gsm)
+{
+	switch (gsm) {
+	case 0:
+		return 0 << 10;
+	case 1:
+		return 1 << 10;
+	case 3:
+	case 9:
+		return 2 << 10;
+	case 10:
+		return 3 << 10;
+	case 11:
+		return 4 << 10;
+	default:
+		die("Bad Graphics Stolen Memory (GSM) setting.\n");
+		return 0;
+	}
+}
+
+u32 get_top_of_ram(void)
+{
+	const device_t dev = PCI_DEV(0, 0, 0);
+
+	u32 tor;
+
+	/* Top of Lower Usable DRAM */
+	tor = (pci_read_config16(dev, D0F0_TOLUD) & 0xfff0) << 16;
+
+	/* Graphics memory comes next */
+	const u32 ggc = pci_read_config16(dev, D0F0_GGC);
+	if (!(ggc & 2)) {
+		/* Graphics memory */
+		tor -= decode_igd_memory_size((ggc >> 4) & 0xf) << 10;
+		/* GTT Graphics Stolen Memory Size (GGMS) */
+		tor -= decode_igd_gtt_size((ggc >> 8) & 0xf) << 10;
+	}
+	return tor;
+}