Radeon X1550 is an entry-level GPU based on the 80nm variant of the R500 architecture.
It's based on the RV516 Core and offers 4 Pixel Shaders, 4 TMUs and 4 ROPs, on a 128-bit of standard DDR. The central unit runs at 550MHz and the memory clock operates at up to 400MHz.
It's therefore an underclocked Radeon X1300 PRO (although a 600MHz version is also available and will offer identical performance) with Crossfire support. As it's not based on a Shader-Unified architecture, both DirectX 10 & 11 games aren't supported.