With AMD's 7700-Series barely out the door speculation has already turned to Pitcairn, AKA the 7800-Series. Broadly a replacement for the 6800-series performance-wise, it too will be based on AMD's 28nm process and Graphics Core Next architecture. Until recently that was as much as we knew about the range, but EXPreview.com have released what they claim to be details of both the 7850 and 7870.
It's believed that Pitcairn XT - AKA the AMD HD7870 - will have 22 Compute Units, 1408 Stream Processors, 88 texture units and 24 ROPs. Core and memory frequencies should be 950MHz and 1375MHz (5500MHz GDDR5) respectively, backed up by 2GB on a 256-bit memory interface.
Pitcairn Pro meanwhile - the 7850 - features 20 CU's, 1208 SPs, 80 texture units and 24 ROPs. It seems likely that 1208 SPs is a misprint which should read 1280, i.e. standard 64 SPs per CU. Core and memory frequencies lag behind those of the 7870 at just 900MHz core and 1.25GHz memory; the 7850 should feature both 2GB and 1GB memory variants on a 256-bit interface.
Retailers are being a little cautious with respect to expected performance level of the 7800-series, perhaps to boost sales of the 6950/70. Even with less than astonishing stock performance designed to compete with the 560 and 560Ti, i.e. 25-35% better than the comparable nVidia SKU, there's no reason to believe that the 7800-series won't overclock just as well as other 28nm parts.
Expreview also mention a supposed salvaged Tahiti variant codenamed Tahiti LE believed to be sold under the 7890 SKU. Featuring 24CUs, 1536 SPs, 96 texture units and 32ROPs, the card should also have the 384-bit memory interface of the full-fat Tahiti's supporting 1.5GB GDDR5 memory. The card is expected in Q2 2012 for $359, straddling the price gap between the 7870 and 7950. Naming it the 7890 rather than 7930 is an oddity, perhaps a hang over from the poor reception of previous AMD HDxx30 parts.
The 7870 is expected to have an MSRP (ex. VAT) of $299, whereas the 7850 will be available for $249 (2GB) and $219 (1GB).
Source: EXPreview.com via Softpedia