Isn't an HDMI to DVI cable a passive cable? That is, are there any DVI monitors that don't also support HDMI over the same connector? Or is that only a standard on newer monitors?
DVI is interesting, because it supports both analog and digital signaling. The analog signaling (DVI-A) is the same signal as VGA, and can be done with a passive adapter; the digital (DVI-D) is the same signal HDMI, and can be done with a passive cable. So, there are monitors that support DVI-A but not DVI-D, and therefore no HDMI; though these are rare.
DVI uses the same digital video signal as HDMI, and passive cables or adapters make it easy to switch between them. I have an older graphics card, one with 1 HDMI port, 1 VGA port, and 1 DVI port. I've got the HDMI and DVI plugged into 2 HDMI monitors.
DVI can also carry an analog video signal. The DVI out on my graphics card can use a passive cable/adapter to VGA. I think DVI was intended as an intermediate standard, so people could use their existing VGA monitors with the possibility of upgrading to digital in the future.
