See https://bugzilla.redhat.com/show_bug.cgi?id=919630 for details.
On my Asus P8H67-V there really are two physically separate audio outputs. I have the optical port connected to my receiver for when I want to pass through the 5.1 audio tracks in movie files and DVDs and the HDMI connected to the TV for more ordinary audio (error beeps from the computer, etc).
There is also internal spdif connector
In kernel 3.7.9 I could output to both devices (one at a time - never tried simultaneous).
I've seen a bunch of patches in the archives that seem to be related to this, but if fedora 18 has those patches, they don't seem to be working.
Have you install the corresponding alsa lib patch ?
https://launchpadlibrarian.net/133258891/alsa-info.txt.riFi7hArcI
Espen Lund mention that he need to perform early patching to change pin default of node 0x11 to spdif out and node 0x1e from spdif RCA to [N/A] for the optical spdif in EVGA X58 SLI Classified which have both coaxial and optical spdif
Node 0x11 [Pin Complex] wcaps 0x400300: Mono Digital Pincap 0x00000010: OUT Pin Default 0x18567130: [Jack] Digital Out at Int HDMI Conn = Digital, Color = Yellow DefAssociation = 0x3, Sequence = 0x0 Misc = NO_PRESENCE Pin-ctls: 0x40: OUT Connection: 1 0x10
Node 0x1e [Pin Complex] wcaps 0x400300: Mono Digital Control: name="SPDIF Phantom Jack", index=0, device=0 Pincap 0x00000010: OUT Pin Default 0x01441120: [Jack] SPDIF Out at Ext Rear Conn = RCA, Color = Black DefAssociation = 0x2, Sequence = 0x0 Misc = NO_PRESENCE Pin-ctls: 0x40: OUT Connection: 1 0x06