SidePort only - In this mode, the integrated graphics core treats the SidePort memory as its local memory.Without SidePort enabled, the CPU needs to be awake to fetch data for refreshing the display, but with SidePort enabled, all memory accesses can occur via the Radeon Xpress 200 and the CPU can remain asleep in power saving modes.Д«ecause of the added cost of supporting SidePort, it isn't a requirement - the Radeon Xpress 200 has four memory operating modes:

So, why would ATI include support for a local frame buffer with the Radeon Xpress 200? Although performance is improved with SidePort enabled, the biggest reason for supporting the feature is to reduce power consumption in mobile environments. It turns out that most games don't benefit too much from lower latency memory accesses (through SidePort). While we assumed that SidePort was included to hide some of the latencies of using the Athlon 64's memory controller, that ended up not being true as performance in UMA mode (using the Athlon 64's memory controller) was quite respectable. The SidePort is a 32-bit DDR memory interface that the integrated graphics can use either instead of or alongside the Athlon 64's memory controller. The Radeon Xpress 200 supports a local frame buffer attached to what ATI refers to as their 'SidePort'. With the Athlon 64, however, the memory controller resides in the CPU, increasing memory access latencies from the perspective of the integrated graphics core. The worries stemmed from the fact that in previous CPU/chipset architectures, the integrated graphics cores resided on the North Bridge and shared access to the system memory controller - also located on the North Bridge.

Just before the launch of the Athlon 64, we found that many chipset manufacturers were a bit worried about the performance of integrated graphics solutions and AMD's new CPU.

Ati radeon xpress 200