(Redirected) Cannot boot from HDD on dell n5010 with both SSD and HDD installed

I have my old dell n5010  ( Inspiron 15R ) with SSD ( Samsung EVO 840 120G) installed on the main drive bay and HDD (Samsung HJJ 500G) on the optical drive bay.

This is a typical way to add a SSD on such an old laptop ( bought from dell.com.cn in 2011 ).

My Windows 10 OS was installed on SSD using Samsung Data Migration software, so the previous C drive was useless. So I formatted it and installed an Ubuntu 14.04 OS on it, hoping start dual OSs from the grub located on the HDD.

However, I cannot find any boot option from the Dell bios to start from the HDD installed on my optical drive bay. All the choices are "Hard Drive", "Network" and "Diagnose".

But I was certainly sure that my bios program had detected both SSD and HDD with the information showed on the main menu of bios.

And the LED on the optical drive bay was lighting immediately after I pressed the start key on my laptop.

Generally, all the things were right except for the bios boot options.

Is there a way I can boot from HDD (with Ubuntu installed) while still have my SSD on the main drive bay? I don't want to exchange their positions because SSD is super fast on the main drive bay.

I alse do not want to migrate Windows 10 back to HDD and re-install Ubuntu on the SSD, because I'd love my Windows be loaded fast.

Does anyone have the same problem with me? 

Any suggestion is appreciated !