diff --git a/py/compile.c b/py/compile.c
index 6fffd9c0bf..5c2fce6866 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -2439,7 +2439,12 @@ STATIC void compile_bytes(compiler_t *comp, mp_parse_node_struct_t *pns) {
 }
 
 STATIC void compile_const_object(compiler_t *comp, mp_parse_node_struct_t *pns) {
+    #if MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_D
+    // nodes are 32-bit pointers, but need to extract 64-bit object
+    EMIT_ARG(load_const_obj, (uint64_t)pns->nodes[0] | ((uint64_t)pns->nodes[1] << 32));
+    #else
     EMIT_ARG(load_const_obj, (mp_obj_t)pns->nodes[0]);
+    #endif
 }
 
 typedef void (*compile_function_t)(compiler_t*, mp_parse_node_struct_t*);
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 01956f63f7..1f01b3de55 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -76,6 +76,19 @@
 
 #define MICROPY_OBJ_REPR_C (2)
 
+// A MicroPython object is a 64-bit word having the following form (called R):
+//  - seeeeeee eeeeffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff 64-bit fp, e != 0x7ff
+//  - s1111111 11110000 00000000 00000000 00000000 00000000 00000000 00000000 +/- inf
+//  - 01111111 11111000 00000000 00000000 00000000 00000000 00000000 00000000 normalised nan
+//  - 01111111 11111101 00000000 00000000 iiiiiiii iiiiiiii iiiiiiii iiiiiii1 small int
+//  - 01111111 11111110 00000000 00000000 qqqqqqqq qqqqqqqq qqqqqqqq qqqqqqq1 str
+//  - 01111111 11111100 00000000 00000000 pppppppp pppppppp pppppppp pppppp00 ptr (4 byte alignment)
+// Stored as O = R + 0x8004000000000000, retrieved as R = O - 0x8004000000000000.
+// This makes pointers have all zeros in the top 32 bits.
+// Small-ints and strs have 1 as LSB to make sure they don't look like pointers
+// to the garbage collector.
+#define MICROPY_OBJ_REPR_D (3)
+
 #ifndef MICROPY_OBJ_REPR
 #define MICROPY_OBJ_REPR (MICROPY_OBJ_REPR_A)
 #endif
diff --git a/py/obj.h b/py/obj.h
index 09c8eda646..174b89ee92 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -32,10 +32,15 @@
 #include "py/mpprint.h"
 
 // All Micro Python objects are at least this type
-// It must be of pointer size
+// The bit-size must be at least pointer size
 
+#if MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_D
+typedef uint64_t mp_obj_t;
+typedef uint64_t mp_const_obj_t;
+#else
 typedef machine_ptr_t mp_obj_t;
 typedef machine_const_ptr_t mp_const_obj_t;
+#endif
 
 // Anything that wants to be a Micro Python object must have
 // mp_obj_base_t as its first member (except small ints and qstrs)
@@ -158,6 +163,56 @@ static inline bool MP_OBJ_IS_QSTR(mp_const_obj_t o)
 static inline bool MP_OBJ_IS_OBJ(mp_const_obj_t o)
     { return ((((mp_int_t)(o)) & 3) == 0); }
 
+#elif MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_D
+
+static inline bool MP_OBJ_IS_SMALL_INT(mp_const_obj_t o)
+    { return ((((mp_int_t)(o)) & 0xffff000000000000) == 0x0001000000000000); }
+#define MP_OBJ_SMALL_INT_VALUE(o) (((intptr_t)(o)) >> 1)
+#define MP_OBJ_NEW_SMALL_INT(small_int) ((mp_obj_t)(((uintptr_t)(small_int)) << 1) | 0x0001000000000001)
+
+static inline bool MP_OBJ_IS_QSTR(mp_const_obj_t o)
+    { return ((((mp_int_t)(o)) & 0xffff000000000000) == 0x0002000000000000); }
+#define MP_OBJ_QSTR_VALUE(o) ((((mp_uint_t)(o)) >> 1) & 0xffffffff)
+#define MP_OBJ_NEW_QSTR(qst) ((mp_obj_t)((((mp_uint_t)(qst)) << 1) | 0x0002000000000001))
+
+#if MICROPY_PY_BUILTINS_FLOAT
+#define mp_const_float_e {((mp_obj_t)((uint64_t)0x4005bf0a8b125769 + 0x8004000000000000))}
+#define mp_const_float_pi {((mp_obj_t)((uint64_t)0x400921fb54442d18 + 0x8004000000000000))}
+
+static inline bool mp_obj_is_float(mp_const_obj_t o) {
+    return ((uint64_t)(o) & 0xfffc000000000000) != 0;
+}
+static inline mp_float_t mp_obj_float_get(mp_const_obj_t o) {
+    union {
+        mp_float_t f;
+        uint64_t r;
+    } num = {.r = o - 0x8004000000000000};
+    return num.f;
+}
+static inline mp_obj_t mp_obj_new_float(mp_float_t f) {
+    union {
+        mp_float_t f;
+        uint64_t r;
+    } num = {.f = f};
+    return num.r + 0x8004000000000000;
+}
+#endif
+
+static inline bool MP_OBJ_IS_OBJ(mp_const_obj_t o)
+    { return ((((uint64_t)(o)) & 0xffff000000000000) == 0x0000000000000000); }
+#define MP_OBJ_TO_PTR(o) ((void*)(uintptr_t)(o))
+#define MP_OBJ_FROM_PTR(p) ((mp_obj_t)((uintptr_t)(p)))
+
+// rom object storage needs special handling to widen 32-bit pointer to 64-bits
+typedef union _mp_rom_obj_t { uint64_t u64; struct { const void *lo, *hi; } u32; } mp_rom_obj_t;
+#define MP_ROM_INT(i) {MP_OBJ_NEW_SMALL_INT(i)}
+#define MP_ROM_QSTR(q) {MP_OBJ_NEW_QSTR(q)}
+#if MP_ENDIANNESS_LITTLE
+#define MP_ROM_PTR(p) {.u32 = {.lo = (p), .hi = NULL}}
+#else
+#define MP_ROM_PTR(p) {.u32 = {.lo = NULL, .hi = (p)}}
+#endif
+
 #endif
 
 // Macros to convert between mp_obj_t and concrete object types.
diff --git a/py/objfloat.c b/py/objfloat.c
index c9e3ddd376..051c0f61c3 100644
--- a/py/objfloat.c
+++ b/py/objfloat.c
@@ -39,7 +39,7 @@
 #include <math.h>
 #include "py/formatfloat.h"
 
-#if MICROPY_OBJ_REPR != MICROPY_OBJ_REPR_C
+#if MICROPY_OBJ_REPR != MICROPY_OBJ_REPR_C && MICROPY_OBJ_REPR != MICROPY_OBJ_REPR_D
 
 typedef struct _mp_obj_float_t {
     mp_obj_base_t base;
@@ -125,7 +125,7 @@ const mp_obj_type_t mp_type_float = {
     .binary_op = float_binary_op,
 };
 
-#if MICROPY_OBJ_REPR != MICROPY_OBJ_REPR_C
+#if MICROPY_OBJ_REPR != MICROPY_OBJ_REPR_C && MICROPY_OBJ_REPR != MICROPY_OBJ_REPR_D
 
 mp_obj_t mp_obj_new_float(mp_float_t value) {
     mp_obj_float_t *o = m_new(mp_obj_float_t, 1);
diff --git a/py/parse.c b/py/parse.c
index afe8711a2d..25aeeae03b 100644
--- a/py/parse.c
+++ b/py/parse.c
@@ -283,7 +283,11 @@ void mp_parse_node_print(mp_parse_node_t pn, mp_uint_t indent) {
         } else if (MP_PARSE_NODE_STRUCT_KIND(pns) == RULE_bytes) {
             printf("literal bytes(%.*s)\n", (int)pns->nodes[1], (char*)pns->nodes[0]);
         } else if (MP_PARSE_NODE_STRUCT_KIND(pns) == RULE_const_object) {
+            #if MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_D
+            printf("literal const(%016llx)\n", (uint64_t)pns->nodes[0] | ((uint64_t)pns->nodes[1] << 32));
+            #else
             printf("literal const(%p)\n", (mp_obj_t)pns->nodes[0]);
+            #endif
         } else {
             mp_uint_t n = MP_PARSE_NODE_STRUCT_NUM_NODES(pns);
 #ifdef USE_RULE_NAME
@@ -362,8 +366,15 @@ STATIC mp_parse_node_t make_node_const_object(parser_t *parser, mp_uint_t src_li
         return MP_PARSE_NODE_NULL;
     }
     pn->source_line = src_line;
+    #if MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_D
+    // nodes are 32-bit pointers, but need to store 64-bit object
+    pn->kind_num_nodes = RULE_const_object | (2 << 8);
+    pn->nodes[0] = (uint64_t)obj;
+    pn->nodes[1] = (uint64_t)obj >> 32;
+    #else
     pn->kind_num_nodes = RULE_const_object | (1 << 8);
     pn->nodes[0] = (mp_uint_t)obj;
+    #endif
     return (mp_parse_node_t)pn;
 }
 
diff --git a/py/smallint.h b/py/smallint.h
index d9e53ee361..0e30a80856 100644
--- a/py/smallint.h
+++ b/py/smallint.h
@@ -46,6 +46,13 @@
 // Mask to truncate mp_int_t to positive value
 #define MP_SMALL_INT_POSITIVE_MASK ~(WORD_MSBIT_HIGH | (WORD_MSBIT_HIGH >> 1) | (WORD_MSBIT_HIGH >> 2))
 
+#elif MICROPY_OBJ_REPR == MICROPY_OBJ_REPR_D
+
+#define MP_SMALL_INT_MIN ((mp_int_t)(((mp_int_t)0xffffffff80000000) >> 1))
+#define MP_SMALL_INT_FITS(n) ((((n) ^ ((n) << 1)) & 0xffffffff80000000) == 0)
+// Mask to truncate mp_int_t to positive value
+#define MP_SMALL_INT_POSITIVE_MASK ~(0xffffffff80000000 | (0xffffffff80000000 >> 1))
+
 #endif
 
 #define MP_SMALL_INT_MAX ((mp_int_t)(~(MP_SMALL_INT_MIN)))