HotHardware posted a review on the AMD ATI Radeon HD 3870 and 3850 video cards

Today AMD finally takes the wraps of their new ATI Radeon HD 3870 and 3850 cards, based on their RV670 GPU. At 55nm and 320 Stream Processors strong, these new cards are set to do battle with the likes of a Geforce 8800 GT and GTS.

"As for the fundamental blocks inside the GPU, the RV670 doesn't differ very much from R600. The RV670 still has 320 stream processing units, 16 texture units, and 16 ROPs. The RV670 however, does away with the 1024-bit internal ring-bus memory controller in favor of a 512-bit variant. And its
memory interface has also been pared down from 512-bits to 256-bit. From high-level perspective, these changes sound-like downgrades, but other tweaks to the GPU negate a massive loss of internal and external bandwidth.

AMD ATI Radeon HD 3870 and 3850: 55nm RV670