Clock rate on MPC8xx CPUs

Clock rate on MPC8xx CPUs

[Robin Gilks]

Greetings

Can anyone shed some light on a question of clock rates?

We're playing with the mpc866ads board and currently running both the
CPU core and bus at 50MHz to keep things simple. As a result it seems
that the internal Linux time is 50% out despite passing the clock rate
from u-boot as being 50MHz.

Since the mpc866 can run its core at x2 the bus rate, does the timer
setup in Linux for this port assume that the CPU _will_ be running at x2
from the rate passed at boot time or is there something else
'interesting' with this new '866 CPU :-))


--
Robin Gilks
Senior Design Engineer              Phone: (+64)(3) 357 1569
Tait Electronics                          Fax  :  (+64)(3) 359 4632
PO Box 1645 Christchurch        Email : robin.gilks@tait.co.nz
New Zealand


** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

Re: Clock rate on MPC8xx CPUs

[Robin Gilks]

Robin Gilks wrote:
>
> Greetings
>
> Can anyone shed some light on a question of clock rates?
>
> We're playing with the mpc866ads board and currently running both the
> CPU core and bus at 50MHz to keep things simple. As a result it seems
> that the internal Linux time is 50% out despite passing the clock rate
> from u-boot as being 50MHz.
>
> Since the mpc866 can run its core at x2 the bus rate, does the timer
> setup in Linux for this port assume that the CPU _will_ be running at x2
> from the rate passed at boot time or is there something else
> 'interesting' with this new '866 CPU :-))

Further questions on the same subject...

Does anyone have a utility that will report the CPU clock rate - we have
confirmed that the bus is running at 50MHz and that the timers are
accurate (so must also be running from the 50MHZ external bus) - but we
still have no definitive value for the clock rate of the CPU core...

--
Robin Gilks
Senior Design Engineer              Phone: (+64)(3) 357 1569
Tait Electronics                          Fax  :  (+64)(3) 359 4632
PO Box 1645 Christchurch        Email : robin.gilks@tait.co.nz
New Zealand


** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/