Acording to a document we've seen, top end ATI cards based on both R520 and R580 actually do not have native HDMI support. Both RV515, Radeon X1300 and RV530, Radeon X1600 have support for HDMI but you do need to add a Silicon Image HDCP chip to make it work.
The X1300 and X1600 HDMI enabled cards will be available by the end of April, but we know that the volumes will be limited due to the low availability of SiL's HDCP chip. SiL claims that it has enough of them but we know that you need to wait some weeks for the chips to be delivered.
I don't know whether ATI plans to include HDMI support in R580+ but it seems that you won't see any X1900 and X1800 cards with HDMI support. We don't know whether G71, Geforce 7900 GT and GTX cards have HDMI support. µ
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