[Carsten Orlt] "The ioHD only outputs 1080i at this stage?"
not true
it is the HDMI 1.1 spec does not support 24/25 playback - it has nothing to do with the geometry - it is the same in 720p also.
The HDMI 1.1 spec did not allow for professional frame rates, since it was designed specifically for consumer use, they did not include any format that was not in the SMTPE delivery spec.
and those were only 50/60 as Interlace or Progressive depending on the frame(geometry)
gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD