AMD sideport memory question.

[Dishum]

This is about the use of sideport memory with an older AMD
chipset. I understand that it frees up a part of the system
memory that would otherwise need to be allocated as a video
buffer. That is, as long as the amount of integrated sideport
memory is enough for the task.

What I'm not quite clear about is whether it also alleviates
traffic on the system bus and thus further helps boost system
performance, even if by a small amount. Englightenment please,
anyone?

 

[Paul]

This is about the use of sideport memory with an older AMD
chipset. I understand that it frees up a part of the system
memory that would otherwise need to be allocated as a video
buffer. That is, as long as the amount of integrated sideport
memory is enough for the task.

What I'm not quite clear about is whether it also alleviates
traffic on the system bus and thus further helps boost system
performance, even if by a small amount. Englightenment please,
anyone?

There's an old article here.

http://www.anandtech.com/show/1537/17

"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. It turns
out that most games don't benefit too much from lower latency
memory accesses (through SidePort). 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. 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."

There are also some benchmarks on that page.

HTH,
Paul