Got it, thanks!

I don't see anything except nonce is incremented in this code. (CPU miner)

bool scanhash_c(int thr_id, const unsigned char *midstate, unsigned char *data,
           unsigned char *hash, const unsigned char *target,
           uint32_t max_nonce, unsigned long *hashes_done)
{
   uint32_t *hash32 = (uint32_t *) hash;
   uint32_t *nonce = (uint32_t *)(data + 12);
   uint32_t n = 0;
   unsigned long stat_ctr = 0;

   work_restart[thr_id].restart = 0;

   while (1) {
      unsigned char hash1[32];

      n++;
      *nonce = n;

      runhash(hash1, data, midstate);
      runhash(hash, hash1, sha256_init_state);

      stat_ctr++;

      if (unlikely((hash32[7] == 0) && fulltest(hash, target))) {
         *hashes_done = stat_ctr;
         return true;
      }

      if ((n >= max_nonce) || work_restart[thr_id].restart) {
         *hashes_done = stat_ctr;
         return false;
      }
   }
}

Hi!
maximum value for unsigned 32 bit integer is 4 294 967 295. So in order to try all the values i need to calculate ~4.3 G of hashes. Then if I have 4.3 GH/s rig I would found it in a second. What I missed?