diff --git a/arch/arm/src/lpc17xx/lpc17_allocateheap.c b/arch/arm/src/lpc17xx/lpc17_allocateheap.c
index 99e0f55e4e6..0f1a96cff87 100644
--- a/arch/arm/src/lpc17xx/lpc17_allocateheap.c
+++ b/arch/arm/src/lpc17xx/lpc17_allocateheap.c
@@ -56,6 +56,7 @@
 #include "lpc17_emacram.h"
 #include "lpc17_ohciram.h"
 #include "lpc17_mpuinit.h"
+#include "lpc17_start.h"
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -248,9 +249,43 @@ void up_allocate_heap(FAR void **heap_start, size_t *heap_size)
   /* Allow user-mode access to the user heap memory */
 
    lpc17_mpu_uheap((uintptr_t)ubase, usize);
+
+#elif CONFIG_MM_REGIONS >= 3 && defined(CONFIG_LPC17_EXTDRAM) && \
+    defined(CONFIG_LPC17_EXTDRAMHEAP)
+  /* We are going to allocate a DRAM heap.  In the case where a bootloader
+   * is used (and has initialized SDRAM), it is possible that .data, .bss,
+   * and the IDLE stack reside in SDRAM.
+   */
+
+    uintptr_t sram_start = CONFIG_RAM_START;
+
+    /* Is SRAM the primary RAM? I.e., do .data, .bss, and the IDLE thread
+     * stack lie in SRAM?
+     */
+
+    if (g_idlestack >= CONFIG_RAM_START &&
+        g_idlestack < CONFIG_RAM_END)
+      {
+        /* Yes, then the SRAM heap starts in SRAM after the IDLE stack */
+
+        sram_start = g_idlestack;
+      }
+    else
+      {
+        /* Use the entire SRAM for heap */
+
+        sram_start = CONFIG_RAM_START;
+      }
+
+  board_autoled_on(LED_HEAPALLOCATE);
+  *heap_start = (FAR void *)sram_start;
+  *heap_size  = CONFIG_RAM_END - sram_start;
+
 #else
 
-  /* Return the heap settings */
+  /* Return the heap settings (assuming that .data, .bss, and the IDLE
+   * stack lie in SRAM).
+   */
 
   board_autoled_on(LED_HEAPALLOCATE);
   *heap_start = (FAR void *)g_idle_topstack;
@@ -266,6 +301,9 @@ void up_allocate_heap(FAR void **heap_start, size_t *heap_size)
  *   user-space heaps (CONFIG_MM_KERNEL_HEAP=y), this function allocates
  *   (and protects) the kernel-space heap.
  *
+ *   REVISIT:  This does not account for the possibility that the kernel
+ *   heap might lie in SDRAM.
+ *
  ****************************************************************************/
 
 #if defined(CONFIG_BUILD_PROTECTED) && defined(CONFIG_MM_KERNEL_HEAP)
@@ -342,38 +380,40 @@ void up_addregion(void)
 
 #if CONFIG_MM_REGIONS >= 3
 #if defined(CONFIG_LPC17_EXTDRAM) && defined(CONFIG_LPC17_EXTDRAMHEAP)
-#if defined(CONFIG_BUILD_PROTECTED) && defined(CONFIG_MM_KERNEL_HEAP)
-  /* Allow user-mode access to external DRAM heap memory */
-
-  lpc17_mpu_uheap((uintptr_t)LPC17_EXTDRAM_CS0, CONFIG_LPC17_EXTDRAMSIZE);
-
-#endif
-  /* Add external DRAM heap memory to the user heap */
   {
-    uint32_t *dram_start = (FAR void *)LPC17_EXTDRAM_CS0;
-    uint32_t *dram_end   = dram_start + CONFIG_LPC17_EXTDRAMSIZE / 4;
+    uintptr_t dram_end = LPC17_EXTDRAM_CS0 + CONFIG_LPC17_EXTDRAMSIZE;
+    uintptr_t dram_start;
+    uintptr_t heap_size;
 
-    if (&_eronly >= dram_start && &_eronly <= dram_end)
+    /* Is SDRAM the primary RAM? I.e., do .data, .bss, and the IDLE thread
+     * stack lie in SDRAM?
+     */
+
+    if (g_idlestack >= LPC17_EXTDRAM_CS0 &&
+        g_idlestack < dram_end)
       {
-        dram_start = (uint32_t *)&_eronly + 0x100;
+        /* Yes, then the SDRAM heap starts in SDRAM after the IDLE stack */
+
+        dram_start = g_idlestack;
+      }
+    else
+      {
+        /* Use the entire SDRAM for heap */
+
+        dram_start = LPC17_EXTDRAM_CS0;
       }
 
-    if (&_edata >= dram_start && &_edata <= dram_end)
-      {
-        dram_start = &_edata + 0x100;
-      }
+    heap_size = dram_end - dram_start;
 
-    if (&_ebss >= dram_start && &_ebss <= dram_end)
-      {
-        dram_start = &_ebss + 0x100;
-      }
+#if defined(CONFIG_BUILD_PROTECTED) && defined(CONFIG_MM_KERNEL_HEAP)
+    /* Allow user-mode access to the external DRAM heap memory */
 
-    if (((uintptr_t)dram_start & 0xff) != 0)
-      {
-        dram_start = (uint32_t *)((uintptr_t)dram_start & ~0xff);
-      }
+    lpc17_mpu_uheap(dram_start, heap_size);
+#endif
 
-    kumm_addregion(dram_start, (char *)dram_end - (char *)dram_start);
+    /* Add external DRAM heap memory to the user heap */
+
+    kumm_addregion(dram_start, heap_size);
   }
 #endif