ATI Radeon HD 4800: Say "No" to the Ring

The RV770 core viewed through a microscope:

You can see that the memory access subsystem has retained its overall topology although it is not a ring anymore. Nearly every memory controller is connected to another one with a bidirectional interface but the ring is not complete. The memory interface is still located at the die’s perimeter. Memory-sensitive functional subunits are placed nearby:

The core has got a switch connecting the subunits that are not sensitive to memory bandwidth such as the PCI Express interface, CrossFireX interface, UVD2 video-processor, display controllers, etc. According to ATI, the memory subsystem resources of previous Radeon HD GPUs were utilized with 85% efficiency while the optimizations implemented in the RV770 make it almost 100%. Coupled with fast GDDR5 memory, this helps the new card do without a wider memory bus while keeping the PCB simple.