Benefit of Dual Channel DDR with Athlon

I've read that Dual Channel works best with Hyper-Threading on the p4
because the CPU can get some work done on one thread while the other
thread is stalled on a memory access.

I've also read that the Athlon has only meager speedups from Dual
Channel since it has no efficient way to switch between threads.

I understand that with DC you have two memory controllers, hence two
paths between memory and the nortbridge. So I am thinking the CPU can
access memory through one channel while the other channel can be used
for DMA to devices connected through the southbridge, notably disk
controllers, anything on the PCI bus, onboard ethernet, USB, etc.

Also you could have a direct path from RAM through the northbridge to
the AGP bus.

So would I be right to say that any application that does a lot of DMA
is likely to benefit quite a bit from Dual Channel?

Matt wrote:
 > I've read that Dual Channel works best with Hyper-Threading on the p4
 > because the CPU can get some work done on one thread while the other
 > thread is stalled on a memory access.
 >
 > I've also read that the Athlon has only meager speedups from Dual
 > Channel since it has no efficient way to switch between threads.
 >
 > I understand that with DC you have two memory controllers, hence two
 > paths between memory and the nortbridge. So I am thinking the CPU can
 > access memory through one channel while the other channel can be used
 > for DMA to devices connected through the southbridge, notably disk
 > controllers, anything on the PCI bus, onboard ethernet, USB, etc.
 >
 > Also you could have a direct path from RAM through the northbridge to
 > the AGP bus.
 >
 > So would I be right to say that any application that does a lot of DMA
 > is likely to benefit quite a bit from Dual Channel?

I think the main point about the Athlon not benefitting as much as the P4 is
that the P4 runs a 800MHz FSB, which matches the 2x400MHz FSB of dual
channel PC3200 RAM perfectly. The Barton core Athlon is still only doing
400MHz though, in effect "wasting" some of the bandwidth of the RAM.

If I read whatever article it was right anyways...

--
RT