ATI Radeon and AMD Radeon are essentially the same product line, with the name change reflecting a corporate acquisition. ATI Technologies, the company that created and branded the Radeon graphics cards, was acquired by AMD (Advanced Micro Devices) in 2006. Before the acquisition, graphics cards were marketed as "ATI Radeon." After AMD took ownership, the branding gradually transitioned to "AMD Radeon," though both names referred to the same underlying technology and product family.
The transition was not instantaneous—for several years after the acquisition, you could find cards branded as either ATI Radeon or AMD Radeon depending on the product line and market. Over time, AMD consolidated the branding entirely under "AMD Radeon" to reflect its ownership. Today, all discrete graphics cards from this product family are marketed exclusively as AMD Radeon.
From a technical standpoint, there is no meaningful difference between cards labeled ATI Radeon versus AMD Radeon—the distinction is purely about corporate ownership and marketing. The architecture, performance, and driver support evolved continuously before, during, and after the transition. If you're comparing specific graphics card models, you should focus on the actual product names and generations (like the Radeon RX 6700, for example) rather than the ATI versus AMD prefix, as that naming convention primarily indicates when the card was released relative to the 2006 acquisition date.