Hello, in message <E19HMrf-0008UY-00.xol-mail-ru at f9.mail.ru> you wrote: > > You r right I've posted same message to > embedded list. I though this is better place for this topic. > Ok, I can get configuration of > CPU 100M > Bus 50M > Or > CPU 80M > Bus 40M > In the worst case second is ok for me, but > I have a luck of performance in my system and do not > want to loose 20% of CPU speed.
There is no other choice. > So I want to find a way how to get > CPU 100M > Bus 40M You cannot. The MPC8xx CPUs gives you two options: you can select the EBDF bits in SCCR either for a divider factor of 1 (bus clock == CPU clock) or 2 (bus clock = CPU clock / 2). No other modes are supported on this platform. > Also I'm driving a PPC Bus via number of boards in the system > and 40M can be problematic. So probably I'll need to > downgrade it to 30/35M. In this case you have to run the CPU at 60 or 70 MHz, resp. > This is reason I can't just use multiplier but have to > find a way control bus speed by myself. You cannot. Bus clock and CPU clock depend on each other, and the only option is a divider factor of 1 or 2. See the documentation for the clocks and the SCCR register in the UM. Best regards, Wolfgang Denk -- Software Engineering: Embedded and Realtime Systems, Embedded Linux Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de Nothing ever becomes real till it is experienced -- even a proverb is no proverb to you till your life has illustrated it. - John Keats ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
