Re: Re: performance of the MPC55XX compared to a TI67XX

Hi Todd,

May I ask why do you run from internal RAM? I mean, first, you need to store the code in flash so you must be copying to RAM and reallocating it before running. I believe that some processors like the MPC families are designed to run from internal flash in one instruction/cycle so you don't gain anything by running from internal RAM. Maybe some people with more knowledge on this can comment, I know it depends a lot on what you do since the internal RAM goes through a different bus than internal flash. There are some technicalities about this, and if I remember correctly, in some cases in the MPC555 for example, that some instructions run slower from internal RAM than from internal flash. I can't comment on TI.
If you are required to run on dsps, keep in mind that the MPC family is not a dsp family. There is a lot of overlap between dsp and micros, but the optimizations play a role.

Regarding the OS, think about it. If your app is so simple that you don't need an OS, then no OS is a good alternative. Sometimes simple schedulers do the job as well. Maybe your requirements don't permit an OS. But my point is, think about it. An OS gives your application a solid framework to run on, and there are some excellent products out there. They make sure your app runs in real-time and that exceptions get handled properly. Nevertheless, in many cases no OS is indeed the best choice.

As George said, don't ignore the startup effort. Getting a CPU running from scratch takes lots of time. Learning to configure the CPU and writing the startup code alone has a learning curve.

I agree with your final conclusion: spend some time testing them hands on. This means not just the CPU, but also the quality of the documentation (crucial), the tools, support, and performance.

Best luck,
-Julian