Its not like the IGP will compete with 256-bit discrete cards, but if you look at the graphs, the IGP is compared with a 8400GS, which only has a 64bit Memory path itself. Suddently its not looking so insignificant.Guys the sideport memory bank is not for performance. It's more of a power saving measure so that you don't need to keep the CPU active when you want to write to VRAM. The sideport buses are usually 16-32bit, just enough to provide the most basic functionality.
Also, consider that the CPU wont be happy if the GPU steals its bandwidth and adds potential latency, so by adding a LFB you both increase total Bandwidth for the IGP and ease up system bandwidth contention.