According to latest reports from HT4U.net, AMD is planning to launch its latest Tahiti LE based Radeon HD 7890 this month on 27th November. The site also mentions that there would be no reference model available at launch but only custom models designed by Add-in-board partners of AMD.
AMD Radeon HD 7890 Availability and Specs
This makes Radeon HD 7890 the first model of the Southern Islands series that won't be available as a reference variant. Also reports are confirming that the Radeon HD 7890 would be a very limited in launch as it is a special variant aimed to attract buyers during the holiday season.
As far as specifications go, the Radeon HD 7890 would be based on the Tahiti LE chip which would feature 1536 Stream processors, 96 Textures Units and 32 ROPs and the memory seems to be 1.5 running across a 384-bit interface. The memory part is yet to be confirmed as earlier we mentioned the card to get a 2GB buffer across a 256-bit interface but our sources are mentioning the 1.5 GB bit to used on Radeon HD 7890.
Pricing would be an important factor to make the card worth its while. We think that the Radeon HD 7890 would cost anywhere between $249-$269 US. Pricing too less makes the Radeon HD 7870 useless and pricing it more would make Radeon HD 7950 seem a better choice. We would get you filled in the performance section of the card in a bit as launch approaches, current estimates are putting the Radeon HD 7890 15% faster than the GeForce GTX 660.