diff --git a/src/northbridge/intel/sandybridge/Kconfig b/src/northbridge/intel/sandybridge/Kconfig
index 0ec4ba2971..16cd697374 100644
--- a/src/northbridge/intel/sandybridge/Kconfig
+++ b/src/northbridge/intel/sandybridge/Kconfig
@@ -90,6 +90,10 @@ config MMCONF_BASE_ADDRESS
 	help
 	  The MRC blob requires it to be at 0xf0000000.
 
+config MMCONF_BUS_NUMBER
+	int
+	default 64
+
 config DCACHE_RAM_BASE
 	hex
 	default 0xfefe0000
diff --git a/src/northbridge/intel/sandybridge/acpi.c b/src/northbridge/intel/sandybridge/acpi.c
index 7ff0fae362..608aa3c68c 100644
--- a/src/northbridge/intel/sandybridge/acpi.c
+++ b/src/northbridge/intel/sandybridge/acpi.c
@@ -11,15 +11,8 @@
 
 unsigned long acpi_fill_mcfg(unsigned long current)
 {
-	u32 length, pciexbar;
-
-	if (!decode_pcie_bar(&pciexbar, &length))
-		return current;
-
-	const int max_buses = length / MiB;
-
-	current += acpi_create_mcfg_mmconfig((acpi_mcfg_mmconfig_t *) current, pciexbar, 0, 0,
-					     max_buses - 1);
+	current += acpi_create_mcfg_mmconfig((acpi_mcfg_mmconfig_t *)current,
+			CONFIG_MMCONF_BASE_ADDRESS, 0, 0, CONFIG_MMCONF_BUS_NUMBER - 1);
 
 	return current;
 }
diff --git a/src/northbridge/intel/sandybridge/bootblock.c b/src/northbridge/intel/sandybridge/bootblock.c
index bea85f4f8e..529f4f886d 100644
--- a/src/northbridge/intel/sandybridge/bootblock.c
+++ b/src/northbridge/intel/sandybridge/bootblock.c
@@ -1,13 +1,23 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #include <arch/bootblock.h>
+#include <assert.h>
 #include <device/pci_ops.h>
+#include <types.h>
 #include "sandybridge.h"
 
+static uint32_t encode_pciexbar_length(void)
+{
+	switch (CONFIG_MMCONF_BUS_NUMBER) {
+		case 256: return 0 << 1;
+		case 128: return 1 << 1;
+		case  64: return 2 << 1;
+		default:  return dead_code_t(uint32_t);
+	}
+}
+
 void bootblock_early_northbridge_init(void)
 {
-	uint32_t reg;
-
 	/*
 	 * The "io" variant of the config access is explicitly used to setup the
 	 * PCIEXBAR because CONFIG(MMCONF_SUPPORT) is set to true. That way, all
@@ -18,8 +28,7 @@ void bootblock_early_northbridge_init(void)
 	 *
 	 * The PCIEXBAR is assumed to live in the memory mapped IO space under 4GiB.
 	 */
-	reg = 0;
-	pci_io_write_config32(HOST_BRIDGE, PCIEXBAR + 4, reg);
-	reg = CONFIG_MMCONF_BASE_ADDRESS | 4 | 1; /* 64MiB - 0-63 buses. */
+	const uint32_t reg = CONFIG_MMCONF_BASE_ADDRESS | encode_pciexbar_length() | 1;
+	pci_io_write_config32(HOST_BRIDGE, PCIEXBAR + 4, 0);
 	pci_io_write_config32(HOST_BRIDGE, PCIEXBAR, reg);
 }
diff --git a/src/northbridge/intel/sandybridge/northbridge.c b/src/northbridge/intel/sandybridge/northbridge.c
index dc1be32ee1..22743553d9 100644
--- a/src/northbridge/intel/sandybridge/northbridge.c
+++ b/src/northbridge/intel/sandybridge/northbridge.c
@@ -35,39 +35,6 @@ bool is_sandybridge(void)
 static const int legacy_hole_base_k = 0xa0000 / 1024;
 static const int legacy_hole_size_k = 384;
 
-int decode_pcie_bar(u32 *const base, u32 *const len)
-{
-	*base = 0;
-	*len = 0;
-
-	struct device *dev = pcidev_on_root(0, 0);
-	if (!dev)
-		return 0;
-
-	const u32 pciexbar_reg = pci_read_config32(dev, PCIEXBAR);
-
-	/* MMCFG not supported or not enabled */
-	if (!(pciexbar_reg & (1 << 0)))
-		return 0;
-
-	switch ((pciexbar_reg >> 1) & 3) {
-	case 0: /* 256MB */
-		*base = pciexbar_reg & (0x0f << 28);
-		*len = 256 * MiB;
-		return 1;
-	case 1: /* 128M */
-		*base = pciexbar_reg & (0x1f << 27);
-		*len = 128 * MiB;
-		return 1;
-	case 2: /* 64M */
-		*base = pciexbar_reg & (0x3f << 26);
-		*len = 64 * MiB;
-		return 1;
-	}
-
-	return 0;
-}
-
 static const char *northbridge_acpi_name(const struct device *dev)
 {
 	if (dev->path.type == DEVICE_PATH_DOMAIN)
@@ -84,10 +51,6 @@ static const char *northbridge_acpi_name(const struct device *dev)
 	return NULL;
 }
 
-/*
- * TODO We could determine how many PCIe busses we need in the bar.
- * For now, that number is hardcoded to a max of 64.
- */
 static struct device_operations pci_domain_ops = {
 	.read_resources    = pci_domain_read_resources,
 	.set_resources     = pci_domain_set_resources,
@@ -126,7 +89,6 @@ static void add_fixed_resources(struct device *dev, int index)
 
 static void mc_read_resources(struct device *dev)
 {
-	u32 pcie_config_base, pcie_config_len;
 	uint64_t tom, me_base, touud;
 	uint32_t tseg_base, uma_size, tolud;
 	uint16_t ggc;
@@ -135,11 +97,7 @@ static void mc_read_resources(struct device *dev)
 
 	pci_dev_read_resources(dev);
 
-	if (decode_pcie_bar(&pcie_config_base, &pcie_config_len)) {
-		const int buses = pcie_config_len / MiB;
-		struct resource *resource = new_resource(dev, PCIEXBAR);
-		mmconf_resource_init(resource, pcie_config_base, buses);
-	}
+	mmconf_resource(dev, PCIEXBAR);
 
 	/* Total Memory 2GB example:
 	 *
diff --git a/src/northbridge/intel/sandybridge/sandybridge.h b/src/northbridge/intel/sandybridge/sandybridge.h
index 235ca0e194..3addd0f4ff 100644
--- a/src/northbridge/intel/sandybridge/sandybridge.h
+++ b/src/northbridge/intel/sandybridge/sandybridge.h
@@ -91,8 +91,6 @@ void perform_raminit(int s3resume);
 void report_memory_config(void);
 enum platform_type get_platform_type(void);
 
-int decode_pcie_bar(u32 *const base, u32 *const len);
-
 #include <device/device.h>
 
 struct acpi_rsdp;