An interesting post on TPU today, Chinese AMD AIB partner Yeston has a Radeon HD 7970 PCB to show, that reportedly is more cost-effective, and it is the  "Tahiti" PCB alright:

It is quite likely that this PCB will be used for Radeon HD 7950, apart from affordable HD 7970 cards. Radeon HD 7950, like its costlier sibling, will have a 384-bit wide GDDR5 memory interface.

Its designers seems to have done some clever cost-cutting which will make cards based on it more affordable (or at least more profitable), without sacrificing quality much. The PCB uses a 8+1+1 phase VRM, consisting of cost-effective ferrite core chokes, LFPAK MOSFETs, and probably a UPI-made VRM controller. Yeston will most likely use a top-flow cooler, and hence made room for two DVI connectors next to one each of HDMI 1.4a and standard DisplayPort 1.2. The dual-BIOS feature of AMD's high-end reference HD 7970 PCB is blanked out on this PCB.