Lost Circuits has just posted a review of Sapphire's flagship Radeon X1900 XTX video card. In typical LostCircuits fashion, Mike goes into great detail on the architecture and explains may of the X1900 GPUs key features. This is a good read.
"Sapphire's repertoire of ATI-based graphics cards has recently been expanded to encompass the X1000 series, which includes the X1900 XT and the X1900 XTX, sporting slightly higher core and memory frequencies than the more plebeian "XT" version. The XTX version is what we are looking at today and to make a long story short, there is little out there that could match the performance of the new Sapphire flagship. So how did they do it? We have heard a few buzzwords here and there about the Ring Bus memory architecture and the quad shader blocks or Fast-Z-Clear but details were sketchy at best, so we started our own investigation with the goal of digesting the information down."