Although the HD 7790 is branded as a HD 7000 series card, it uses an entirely new GPU (entitled “Bonaire”) and is actually a part of the next generation Sea Islands GPU family, rather than the Southern Islands GPU family. While a new GPU microarchitecture usually constitutes a new generation branding for both nVIDIA and AMD, AMD announced earlier that it would continue to utilize the HD 7000 branding, due to the popularity of the Radeon HD 7000 series.
Reviews of the Radeon HD 7790 can be found at on various tech sites:
AnandTech – AMD Radeon HD 7790 Review Feat. Sapphire: The First Desktop Sea Islands
[H]ard|OCP – ASUS Radeon HD 7790 DirectCU II OC Video Card Review
TechReport – AMD’s Radeon HD 7790 graphics card reviewed
Guru3D – Radeon HD 7790 Review
Tom’s Hardware – AMD Radeon HD 7790 Review: Graphics Core Next At $150
Despite being limited to a 128-bit memory bus and having less than half of the ROPs found in the Radeon HD 7850, it performs well and is even comparable in performance with the HD 7850 in some games/applications. As part of the new Sea Islands GPU family, this is pretty promising and should be interesting to see how a high-end Sea Islands GPU (HD 7975? HD 7995?) performs.