Radeon X300-X600 series

ATI released the Radeon X300 and X600 boards. These were based on the "RV370" (110 nm process) and "RV380" (130 nm Low-K process) GPU respectively. They were nearly identical to the chips used in Radeon 9550 and 9600, only differing in that they were native PCI Express offerings. These were very popular for Dell and other OEM companies to sell in various configurations; connectors: DVI vs. DMS-59, card height: full-height vs. half-height.
Later the Radeon X550 was launched, using the same chip as Radeon X300 graphics card (RV370).