diff --git a/stm/gccollect.c b/stm/gccollect.c
index cea0bc56e..ada5493a2 100644
--- a/stm/gccollect.c
+++ b/stm/gccollect.c
@@ -13,10 +13,10 @@ void gc_helper_get_regs_and_clean_stack(machine_uint_t *regs, machine_uint_t hea
 void gc_collect(void) {
     uint32_t start = sys_tick_counter;
     gc_collect_start();
-    gc_collect_root((void**)&_ram_start, (&_heap_start - &_ram_start) / 4);
+    gc_collect_root((void**)&_ram_start, ((uint32_t)&_heap_start - (uint32_t)&_ram_start) / sizeof(uint32_t));
     machine_uint_t regs[10];
     gc_helper_get_regs_and_clean_stack(regs, (machine_uint_t)&_heap_end);
-    gc_collect_root((void**)&_heap_end, (&_ram_end - &_heap_end) / 4); // will trace regs since they now live in this function on the stack
+    gc_collect_root((void**)&_heap_end, ((uint32_t)&_ram_end - (uint32_t)&_heap_end) / sizeof(uint32_t)); // will trace regs since they now live in this function on the stack
     gc_collect_end();
     uint32_t ticks = sys_tick_counter - start; // TODO implement a function that does this properly
 
diff --git a/stm/main.c b/stm/main.c
index 9f2b6d564..5c2d3cf17 100644
--- a/stm/main.c
+++ b/stm/main.c
@@ -174,15 +174,24 @@ static mp_obj_t pyb_info(void) {
         extern void *_ebss;
         extern void *_estack;
         extern void *_etext;
+        printf("_etext=%p\n", &_etext);
         printf("_sidata=%p\n", &_sidata);
         printf("_sdata=%p\n", &_sdata);
         printf("_edata=%p\n", &_edata);
         printf("_sbss=%p\n", &_sbss);
         printf("_ebss=%p\n", &_ebss);
         printf("_estack=%p\n", &_estack);
-        printf("_etext=%p\n", &_etext);
         printf("_ram_start=%p\n", &_ram_start);
         printf("_heap_start=%p\n", &_heap_start);
+        printf("_heap_end=%p\n", &_heap_end);
+        printf("_ram_end=%p\n", &_ram_end);
+    }
+
+    // qstr info
+    {
+        uint n_pool, n_qstr, n_str_data_bytes, n_total_bytes;
+        qstr_pool_info(&n_pool, &n_qstr, &n_str_data_bytes, &n_total_bytes);
+        printf("qstr:\n  n_pool=%u\n  n_qstr=%u\n  n_str_data_bytes=%u\n  n_total_bytes=%u\n", n_pool, n_qstr, n_str_data_bytes, n_total_bytes);
     }
 
     // GC info
diff --git a/stm/stm32f405.ld b/stm/stm32f405.ld
index 5cef201a9..6c29a681c 100644
--- a/stm/stm32f405.ld
+++ b/stm/stm32f405.ld
@@ -19,8 +19,9 @@ _minimum_heap_size = 16K;
 /* top end of the stack */
 _estack = ORIGIN(RAM) + LENGTH(RAM);
 
-_ram_end = 0x20020000;
-_heap_end = 0x2001c000;
+/* RAM extents for the garbage collector */
+_ram_end = ORIGIN(RAM) + LENGTH(RAM);
+_heap_end = 0x2001c000; /* tunable */
 
 /* define output sections */
 SECTIONS