Dear Guowen SHAN,
In message cf7369060903290628p2768907p9a0c2e40c898601b@mail.gmail.com you wrote:
I'm porting u-boot-1.3.1 to customer board, which includes MPC850 and
32MB SDRAM.
When I turned off icache, bus can work correctly under 25MHz/50MHz clock
frequence.
Note that CPU is working under 50MHz. However, the board only can work
with bus
frequence of 25MHz with enabled icache. If I tried to set bus frequence
to 50MHz with
enabled icache, it will crash with MCE.
Easy problem - actually FAQ: please see http://www.denx.de/wiki/view/DULG/UBootCrashAfterRelocation
I don't understand it completely. 25MHz with enabled icache could use burst to fecth instructions from RAM, which should have proved the UPM words and initialization sequence was ok, right?
http://www.denx.de/wiki/view/DULG/UBootCrashAfterRelocation
I don't know why. Since it can work at 25MHz with enabled icache, the UPM
words seem
ok. Thanks for your advices!
Keep in mind that the UPM setup is only part of the required RAM initialization sequence. Follow the instructions in the chip manufacturer's manual to the letter.