ATI Radeon HD 4000 Series discussion

[Shintai]

I wonder what they mean about that "4D+1D". Is it that every group of five SPs has a more complete unit like the R6xx?

Its precisely as today. R600/RV670 is 64SP that is 4+1. With marketing it becomes 320 (nVidia should be 256 then). So its simply a 50% SP increase over the 600 series.