The IDE interface does not support extending the hard drive away from the board (as in the case of a splitter cable) and does not support multiple devices. I have read that doing so not only will not work, but could damage the EFIKA.
I have got a CD-ROM drive on my EFIKA connected by USB. I'm not using a slim drive, but you could use something like
this. Take the guts out and there will just be a little PCB which will connect to the CD-ROM drive and convert it to USB.
Note that I have no idea whether that particular one will work on the EFIKA or fit your optical drive. It's just an idea. My only experience is with a standard 5.25" CD-ROM and a 40 way IDE->USB1.1 converter, which worked.
The adapter I use is
this one.
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moto