diff --git a/src/mainboard/apple/macbookair4_2/devicetree.cb b/src/mainboard/apple/macbookair4_2/devicetree.cb
index a43b9f2..226ec04 100644
--- a/src/mainboard/apple/macbookair4_2/devicetree.cb
+++ b/src/mainboard/apple/macbookair4_2/devicetree.cb
@@ -30,6 +30,9 @@
 			end
 		end
 	end
+
+	register "pci_mmio_size" = "2048"
+
 	device domain 0x0 on
 		chip southbridge/intel/bd82x6x # Intel Series 6 Cougar Point PCH
 			register "c2_latency" = "0x0065"
diff --git a/src/mainboard/gigabyte/ga-b75m-d3h/devicetree.cb b/src/mainboard/gigabyte/ga-b75m-d3h/devicetree.cb
index f4a8664..2cd3816 100644
--- a/src/mainboard/gigabyte/ga-b75m-d3h/devicetree.cb
+++ b/src/mainboard/gigabyte/ga-b75m-d3h/devicetree.cb
@@ -19,6 +19,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		subsystemid 0x1458 0x5000 inherit
 		device pci 00.0 on # host bridge
diff --git a/src/mainboard/gigabyte/ga-b75m-d3v/devicetree.cb b/src/mainboard/gigabyte/ga-b75m-d3v/devicetree.cb
index 5ed7ec3..618943c 100644
--- a/src/mainboard/gigabyte/ga-b75m-d3v/devicetree.cb
+++ b/src/mainboard/gigabyte/ga-b75m-d3v/devicetree.cb
@@ -18,6 +18,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		subsystemid 0x1458 0x5000 inherit
 		device pci 00.0 on # host bridge
diff --git a/src/mainboard/google/stout/devicetree.cb b/src/mainboard/google/stout/devicetree.cb
index 6c693ad..76f2856 100644
--- a/src/mainboard/google/stout/devicetree.cb
+++ b/src/mainboard/google/stout/devicetree.cb
@@ -42,6 +42,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "1024"
+
 	device domain 0 on
 		subsystemid 0x1ae0 0xc000 inherit
 		device pci 00.0 on end # host bridge
diff --git a/src/mainboard/lenovo/t400/devicetree.cb b/src/mainboard/lenovo/t400/devicetree.cb
index 7923046..43a610a 100644
--- a/src/mainboard/lenovo/t400/devicetree.cb
+++ b/src/mainboard/lenovo/t400/devicetree.cb
@@ -23,6 +23,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		device pci 00.0 on
 			subsystemid 0x17aa 0x20e0
diff --git a/src/mainboard/lenovo/t420/devicetree.cb b/src/mainboard/lenovo/t420/devicetree.cb
index 9f42cbb..809e3ee 100644
--- a/src/mainboard/lenovo/t420/devicetree.cb
+++ b/src/mainboard/lenovo/t420/devicetree.cb
@@ -36,6 +36,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		device pci 00.0 on
 			subsystemid 0x17aa 0x21ce
diff --git a/src/mainboard/lenovo/t420s/devicetree.cb b/src/mainboard/lenovo/t420s/devicetree.cb
index 2376d64..841e675 100644
--- a/src/mainboard/lenovo/t420s/devicetree.cb
+++ b/src/mainboard/lenovo/t420s/devicetree.cb
@@ -35,6 +35,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		device pci 00.0 on
 			subsystemid 0x17aa 0x21d2
diff --git a/src/mainboard/lenovo/t430s/devicetree.cb b/src/mainboard/lenovo/t430s/devicetree.cb
index 8c0f10f..d1cea3c 100644
--- a/src/mainboard/lenovo/t430s/devicetree.cb
+++ b/src/mainboard/lenovo/t430s/devicetree.cb
@@ -35,6 +35,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		device pci 00.0 on
 			subsystemid 0x17aa 0x21fb
diff --git a/src/mainboard/lenovo/t520/devicetree.cb b/src/mainboard/lenovo/t520/devicetree.cb
index 379a95d..c0292ec 100644
--- a/src/mainboard/lenovo/t520/devicetree.cb
+++ b/src/mainboard/lenovo/t520/devicetree.cb
@@ -36,6 +36,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		device pci 00.0 on end # host bridge
 		device pci 01.0 on end # NVIDIA Corporation GF119M [NVS 4200M]
diff --git a/src/mainboard/lenovo/t530/devicetree.cb b/src/mainboard/lenovo/t530/devicetree.cb
index 7db65c7..43d8264 100644
--- a/src/mainboard/lenovo/t530/devicetree.cb
+++ b/src/mainboard/lenovo/t530/devicetree.cb
@@ -36,6 +36,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		device pci 00.0 on end # host bridge
 		device pci 01.0 on end # PCIe Bridge for discrete graphics
diff --git a/src/mainboard/lenovo/x200/devicetree.cb b/src/mainboard/lenovo/x200/devicetree.cb
index 92c41d7..9f5bb41 100644
--- a/src/mainboard/lenovo/x200/devicetree.cb
+++ b/src/mainboard/lenovo/x200/devicetree.cb
@@ -28,6 +28,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "1024"
+
 	device domain 0 on
 		device pci 00.0 on
 			subsystemid 0x17aa 0x20e0
diff --git a/src/mainboard/lenovo/x201/devicetree.cb b/src/mainboard/lenovo/x201/devicetree.cb
index 2374554..bd6490e 100644
--- a/src/mainboard/lenovo/x201/devicetree.cb
+++ b/src/mainboard/lenovo/x201/devicetree.cb
@@ -80,6 +80,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "1024"
+
 	device domain 0 on
 		device pci 00.0 on # Host bridge
 			subsystemid 0x17aa 0x2193
diff --git a/src/mainboard/lenovo/x220/devicetree.cb b/src/mainboard/lenovo/x220/devicetree.cb
index 6f84acd..af70b20 100644
--- a/src/mainboard/lenovo/x220/devicetree.cb
+++ b/src/mainboard/lenovo/x220/devicetree.cb
@@ -36,6 +36,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "1024"
+
 	device domain 0 on
 		device pci 00.0 on
 			subsystemid 0x17aa 0x21db
diff --git a/src/mainboard/lenovo/x230/devicetree.cb b/src/mainboard/lenovo/x230/devicetree.cb
index 37d53d4..f0c940d 100644
--- a/src/mainboard/lenovo/x230/devicetree.cb
+++ b/src/mainboard/lenovo/x230/devicetree.cb
@@ -36,6 +36,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "1024"
+
 	device domain 0 on
 		device pci 00.0 on
 			subsystemid 0x17aa 0x21fa
diff --git a/src/mainboard/packardbell/ms2290/devicetree.cb b/src/mainboard/packardbell/ms2290/devicetree.cb
index 12ce648..bb4e854 100644
--- a/src/mainboard/packardbell/ms2290/devicetree.cb
+++ b/src/mainboard/packardbell/ms2290/devicetree.cb
@@ -42,6 +42,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		device pci 00.0 on # Host bridge
 			subsystemid 0x1025 0x0379
diff --git a/src/mainboard/roda/rk9/devicetree.cb b/src/mainboard/roda/rk9/devicetree.cb
index 003c08e..690c2a5 100644
--- a/src/mainboard/roda/rk9/devicetree.cb
+++ b/src/mainboard/roda/rk9/devicetree.cb
@@ -19,6 +19,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "2048"
+
 	device domain 0 on
 		subsystemid 0x4352 0x8986
 		device pci 00.0 on end # host bridge
diff --git a/src/mainboard/samsung/lumpy/devicetree.cb b/src/mainboard/samsung/lumpy/devicetree.cb
index f73e6039..0dd3228 100644
--- a/src/mainboard/samsung/lumpy/devicetree.cb
+++ b/src/mainboard/samsung/lumpy/devicetree.cb
@@ -34,6 +34,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "1024"
+
 	device domain 0 on
 		ioapic_irq 4 INTA 0x10
 		ioapic_irq 4 INTB 0x11
diff --git a/src/mainboard/samsung/stumpy/devicetree.cb b/src/mainboard/samsung/stumpy/devicetree.cb
index 901711b..adc15e6 100644
--- a/src/mainboard/samsung/stumpy/devicetree.cb
+++ b/src/mainboard/samsung/stumpy/devicetree.cb
@@ -32,6 +32,8 @@
 		end
 	end
 
+	register "pci_mmio_size" = "1024"
+
 	device domain 0 on
 		subsystemid 0x1ae0 0xc000 inherit
 		device pci 00.0 on end # host bridge
diff --git a/src/northbridge/intel/gm45/chip.h b/src/northbridge/intel/gm45/chip.h
index b537b93..836d6bb 100644
--- a/src/northbridge/intel/gm45/chip.h
+++ b/src/northbridge/intel/gm45/chip.h
@@ -26,6 +26,11 @@
 	u16 gpu_panel_power_backlight_off_delay; /* Tx time sequence */
 	u8 gpu_panel_power_cycle_delay;          /* T4 time sequence */
 	struct i915_gpu_controller_info gfx;
+
+	/*
+	 * Maximum PCI mmio size in MiB.
+	 */
+	u16 pci_mmio_size;
 };
 
 #endif				/* NORTHBRIDGE_INTEL_GM45_CHIP_H */
diff --git a/src/northbridge/intel/gm45/raminit.c b/src/northbridge/intel/gm45/raminit.c
index ab54abc..37b44cc 100644
--- a/src/northbridge/intel/gm45/raminit.c
+++ b/src/northbridge/intel/gm45/raminit.c
@@ -20,11 +20,13 @@
 #include <arch/io.h>
 #include <device/pci_def.h>
 #include <device/pnp_def.h>
+#include <device/device.h>
 #include <spd.h>
 #include <console/console.h>
 #include <lib.h>
 #include "delay.h"
 #include "gm45.h"
+#include "chip.h"
 
 static const gmch_gfx_t gmch_gfx_types[][5] = {
 /*  MAX_667MHz    MAX_533MHz    MAX_400MHz    MAX_333MHz    MAX_800MHz    */
@@ -1156,6 +1158,25 @@
 	EPBAR32(0x3c) = timings_by_fsb[fsb][1];
 }
 
+#define DEFAULT_PCI_MMIO_SIZE 2048
+#define HOST_BRIDGE	PCI_DEVFN(0, 0)
+
+static unsigned int get_mmio_size(void)
+{
+	const struct device *dev;
+	const struct northbridge_intel_gm45_config *cfg = NULL;
+
+	dev = dev_find_slot(0, HOST_BRIDGE);
+	if (dev)
+		cfg = dev->chip_info;
+
+	/* If this is zero, it just means devicetree.cb didn't set it */
+	if (!cfg || cfg->pci_mmio_size == 0)
+		return DEFAULT_PCI_MMIO_SIZE;
+	else
+		return cfg->pci_mmio_size;
+}
+
 /* @prejedec if not zero, set rank size to 128MB and page size to 4KB. */
 static void program_memory_map(const dimminfo_t *const dimms, const channel_mode_t mode, const int prejedec, u16 ggc)
 {
@@ -1226,7 +1247,8 @@
 		}
 	}
 
-	const unsigned int MMIOstart = 0x0c00 + uma_sizem; /* 3GB, makes MTRR configuration small. */
+	const unsigned int mmio_size = get_mmio_size();
+	const unsigned int MMIOstart = 4096 - mmio_size + uma_sizem;
 	const int me_active = pci_read_config8(PCI_DEV(0, 3, 0), PCI_CLASS_REVISION) != 0xff;
 	const unsigned int ME_SIZE = prejedec || !me_active ? 0 : 32;
 	const unsigned int usedMEsize = (total_mb[0] != total_mb[1]) ? ME_SIZE : 2 * ME_SIZE;
diff --git a/src/northbridge/intel/nehalem/chip.h b/src/northbridge/intel/nehalem/chip.h
index caf9819..a9d136b 100644
--- a/src/northbridge/intel/nehalem/chip.h
+++ b/src/northbridge/intel/nehalem/chip.h
@@ -41,6 +41,11 @@
 	u32 gpu_pch_backlight;	/* PCH Backlight PWM value */
 
 	struct i915_gpu_controller_info gfx;
+
+	/*
+	 * Maximum PCI mmio size in MiB.
+	 */
+	u16 pci_mmio_size;
 };
 
 #endif /* NORTHBRIDGE_INTEL_NEHALEM_CHIP_H */
diff --git a/src/northbridge/intel/nehalem/raminit.c b/src/northbridge/intel/nehalem/raminit.c
index 0549de7..69e7108 100644
--- a/src/northbridge/intel/nehalem/raminit.c
+++ b/src/northbridge/intel/nehalem/raminit.c
@@ -32,10 +32,12 @@
 #include <ip_checksum.h>
 #include <pc80/mc146818rtc.h>
 #include <device/pci_def.h>
+#include <device/device.h>
 #include <arch/cpu.h>
 #include <halt.h>
 #include <spd.h>
 #include "raminit.h"
+#include "chip.h"
 #include <timestamp.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/intel/speedstep.h>
@@ -1450,6 +1452,25 @@
 	}
 }
 
+#define DEFAULT_PCI_MMIO_SIZE 2048
+#define HOST_BRIDGE	PCI_DEVFN(0, 0)
+
+static unsigned int get_mmio_size(void)
+{
+	const struct device *dev;
+	const struct northbridge_intel_nehalem_config *cfg = NULL;
+
+	dev = dev_find_slot(0, HOST_BRIDGE);
+	if (dev)
+		cfg = dev->chip_info;
+
+	/* If this is zero, it just means devicetree.cb didn't set it */
+	if (!cfg || cfg->pci_mmio_size == 0)
+		return DEFAULT_PCI_MMIO_SIZE;
+	else
+		return cfg->pci_mmio_size;
+}
+
 #define BETTER_MEMORY_MAP 0
 
 static void program_total_memory_map(struct raminfo *info)
@@ -1459,6 +1480,7 @@
 	unsigned int REMAPbase;
 	unsigned int uma_base_igd;
 	unsigned int uma_base_gtt;
+	unsigned int mmio_size;
 	int memory_remap;
 	unsigned int memory_map[8];
 	int i;
@@ -1485,11 +1507,13 @@
 	}
 #endif
 
+	mmio_size = get_mmio_size();
+
 	TOM = info->total_memory_mb;
 	if (TOM == 4096)
 		TOM = 4032;
 	TOUUD = ALIGN_DOWN(TOM - info->memory_reserved_for_heci_mb, 64);
-	TOLUD = ALIGN_DOWN(min(3072 + ALIGN_UP(uma_size_igd + uma_size_gtt, 64)
+	TOLUD = ALIGN_DOWN(min(4096 - mmio_size + ALIGN_UP(uma_size_igd + uma_size_gtt, 64)
 			       , TOUUD), 64);
 	memory_remap = 0;
 	if (TOUUD - TOLUD > 64) {
diff --git a/src/northbridge/intel/sandybridge/chip.h b/src/northbridge/intel/sandybridge/chip.h
index 5effc0d..d002824 100644
--- a/src/northbridge/intel/sandybridge/chip.h
+++ b/src/northbridge/intel/sandybridge/chip.h
@@ -47,6 +47,11 @@
 	u16 max_mem_clock_mhz;
 
 	struct i915_gpu_controller_info gfx;
+
+	/*
+	 * Maximum PCI mmio size in MiB.
+	 */
+	u16 pci_mmio_size;
 };
 
 #endif /* NORTHBRIDGE_INTEL_SANDYBRIDGE_CHIP_H */
diff --git a/src/northbridge/intel/sandybridge/raminit.c b/src/northbridge/intel/sandybridge/raminit.c
index 6bb77b2..4563547 100644
--- a/src/northbridge/intel/sandybridge/raminit.c
+++ b/src/northbridge/intel/sandybridge/raminit.c
@@ -204,6 +204,7 @@
 #define GET_ERR_CHANNEL(x) (x>>16)
 
 static void program_timings(ramctr_timing * ctrl, int channel);
+static unsigned int get_mmio_size(void);
 
 static const char *ecc_decoder[] = {
 	"inactive",
@@ -1086,7 +1087,7 @@
 	size_t tsegbasedelta, remapbase, remaplimit;
 	uint16_t ggc;
 
-	mmiosize = 0x400;
+	mmiosize = get_mmio_size();
 
 	ggc = pci_read_config16(NORTHBRIDGE, GGC);
 	if (!(ggc & 2)) {
@@ -4384,6 +4385,24 @@
 	}
 }
 
+#define DEFAULT_PCI_MMIO_SIZE 2048
+
+static unsigned int get_mmio_size(void)
+{
+	const struct device *dev;
+	const struct northbridge_intel_sandybridge_config *cfg = NULL;
+
+	dev = dev_find_slot(0, HOST_BRIDGE);
+	if (dev)
+		cfg = dev->chip_info;
+
+	/* If this is zero, it just means devicetree.cb didn't set it */
+	if (!cfg || cfg->pci_mmio_size == 0)
+		return DEFAULT_PCI_MMIO_SIZE;
+	else
+		return cfg->pci_mmio_size;
+}
+
 void perform_raminit(int s3resume)
 {
 	spd_raw_data spd[4];