Some details about AMD's upcoming low-end and mid-range Radeon HD 4000 series GPUs were published at Nordic Hardware. The site says AMD will launch two RV710 and two RV730 graphics cards and the difference will be in the memory speeds or capacity.
Two different GDDR3 memory configurations can be seen with RV710. Both memory operates at 800MHz, but the density varies from 512MB Hynix memory to 1024MB Samsung chips. This points to that the 4450 and 4470 models will be separated by GPU clock. We need to confirm the exact specifications of both RV710 and RV730 before revealing more about them. No 256MB models could be spotted in the document.
RV730 offers a bit more variation as we notice three different clock frequencies and two different densities. One 700MHz 512MB model, and two 900MHz models, whereof one sports 512MB Hynix memory and one sports 1024MB Samsung chips. Last but not least there is one model with 512MB Hynix memory operating at 1000MHz. We would assume Radeon HD 4650 is the 700MHz cards, while the 4670 model is represented by the three remaining cards.