The Radeon X550 core is the RV370 and it will use the same PCBs as the previous RV370 boards (X300), but AIBs are allowed to make modifications such as a reduced PCB layer count.
If you are not familiar with RV370, the chip uses four rendering pipelines and two vertex shaders. Clock speeds of the X550 are 400 MHz Core and 250 MHz Memory. Which means that most designs will use TSOP DDR1. Available bus bandwidths are 64 and 128 bit, like all existing RV370 designs. Memory size can be varied from 64 MB to 256 MB.The card will likely be launched by mid-June or early July for a price of $60.