Ricardo Raupp wrote:
>
> Hi people
> Could someone show me a comparsion between Linux and uClinux for ColdFires?
> I´m deciding between a V2 (5274L) x a V4 (54450) core.
> The main diference I noticed ( or almost the) is V4 has MMU, wich enable
> Linux on it.
> The chips cost is very close...I´m tending to a V4 chip..
> Thanks
>
The difference between ucLinux and Linux is that ucLinux works without
an MMU (you can also use it on a cpu with an MMU if you want). ucLinux
works mostly like Linux, but has a few limitations:
You don't get protection between processes memory spaces (obviously), so
a bad process can stomp on good processes.
You can't use "fork" - you must use "vfork" to replace "fork + exec"
combinations. This may mean changing existing Linux code to port it to
ucLinux - for most applications, it's a minor issue, but it can be a
problem if you want to run traditional unix-style forking servers.
You can't use virtual memory. Even if you are not using external page
files, virtual memory and the MMU can help avoid fragmentation of main
memory.
I'm not sure on this one, but I don't think you can nmap files in ucLinux.
For small systems where you have complete control over which processes
will run on the system, ucLinux is often perfectly good, and can be
faster than plain Linux since MMU's can add a delay to memory access.
As for the V2 versus the V4 - you get more processing power for your
money with a V4, but more microcontroller-style peripherals with most V2
devices, and a V2 board is going to be easier and cheaper to make. But
that depends on the sort of boards you are used to making.
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