MPC8313 performance evaluation

[Liu Dave-R63238]

> > On Aug 6, 2009, at 1:00 PM, Lutz Jaenicke wrote:
> >> With the MPC8343 at 400MHz I get a throughput of approx. 
> 24500 frames/s
> >> using the predefined firewall rules.
> 
> >> With the MPC8313 I get a significantly lower value:
> >> MPC8313 at 250MHz          12500fps
> >> MPC8313 at 333MHz          14500fps
> >> MPC8313 at 416MHz          15500fps      (333MHz type, overclocked)
> 
> > What DDR frequencies (and width) are you running the 8343 
> vs 8313 at.   
> > This can have a significant impact on performance.
> 
> The 8343 is running DDR2 32bit at 266MHz (CSB 266MHz)
> The 8313 is running DDR2 32bit at 333MHz (CSB 166MHz)
> 
> The test were performed with 128byte frames so that the overall
> bandwidth needed is far below even 100Mbit/s.

The CSB bus freq is key for the throught.
CSB freq of 8313 is lower than 8343, it will cause the performance
degrade.