Originally Posted by PanamaMike
Is the bottleneck the Atom or is it the disk controller? I'd have to guess disk controller.
I think it is the single channel memory controller on the Atom coupled
with the small cache. (The Mobi is 100Mbs read and write, SATA1
would not have bottlenecked it))
The SATA controller transfers data directly to memory, and while that is
happening the CPU cannot access memory.
If the data is in cache then it can continue to work otherwise it is
stalled until the io transfer completes.
Windows chops the disk accesses into multiple iorequests, and the CPU
competes with the SATA controller to get to the memory controller for
the duration of the transfer.
When the CPU is data starved the apps slow down and this partially
cancels out the faster data access from the SSD.
A fast SSD puts a lot of pressure on the mechanism the faster it goes.
This is where the C2D has the upper hand. The memory subsystem is
2X faster (dual channel) and there is 4X the cache (2M vs 512k) on the
T5600. So the on the C2D the SATA controller will take less time to
complete the transfer (for a given block size). If the CPU has to
wait, the chances of a stall is reduced as the cache is larger and probablity
of finding the executable code is higher
Intel has made some attempts to address this as the memory controller
runs at 667/800MHz on the D510 as opposed to 533MHz on the N330.
The CPU fsb is unchanged at 533MHz.
With careful tuning of the kernel working set the Atom can produce good IO
thruput. A lot of Atom NAS vendors use Linux because of this.
The difference here is that the custom OS kernel does not have to
deal with general desktop duties.