• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 102 subscribers
  • Views 518 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AM3352 Does OPP mode denote clock/RAM speed?

Tim Chao Li
Expert 4415 points
Other Parts Discussed in Thread: AM3352

We have an AM3352 question about the CPU clock speed. We are using the 800MHz speed grade which we plan to boot at that rate and then switch down to 300MHz afterwards. We came across some info (see the URL in the email below) that says that OPP50 mode disables Ethernet and DDR3 support.  We were wondering:

  1. Does setting the CPU to OPP50 inherently set the CPU clock to 300MHz?
  2. Does setting the CPU to 300MHz inherently set the CPU to OPP50?
  3. If the above two things are not the same, how do you set the OPP mode?  We have been using the cpufreq-info command in both Angstrom and Arago Linux to view and adjust the clock frequency.  Can this command be used to set the OPP mode too?
  4. Does the OPP mode affect the RAM speed too? Or does the RAM always run at the same speed from boot onward?

http://www.ti.com/product/AM3358/datasheet/peripheral_information_and_timings#SPRS7174426

  • 0
    TI__Guru**** 393215 points

    Hi Tim,

    Tim Chao Li said:
    Does setting the CPU to OPP50 inherently set the CPU clock to 300MHz?

    Yes, 300MHz is the maximum clock frequency for MPU OPP50.

    Tim Chao Li said:
    Does setting the CPU to 300MHz inherently set the CPU to OPP50?

    No, this is not necessarily true. You can lower the frequency without changing the OPP. The frequencies for each OPP in the datasheet are the maximum possible for a given OPP.

    Tim Chao Li said:
    If the above two things are not the same, how do you set the OPP mode?  We have been using the cpufreq-info command in both Angstrom and Arago Linux to view and adjust the clock frequency.  Can this command be used to set the OPP mode too?

    See this wiki: http://processors.wiki.ti.com/index.php/Linux_Core_Power_Management_User's_Guide

    Tim Chao Li said:
    Does the OPP mode affect the RAM speed too? Or does the RAM always run at the same speed from boot onward?

    DDR maximum frequency is different (lower) for OPP50, and DDR3 cannot be used in OPP50.

  • 0 in reply to Biser Gatchev-XID
    TI__Guru*** 125430 points

    Throwing in my own two cents...

    It seems to me that there may be some confusion in this thread between "MPU OPPs" and "CORE OPPs".  The two are independent (mostly).  The DDR frequency is dictated by the CORE OPP which can be OPP50 or OPP100.  As Biser mentioned, with CORE OPP50 you cannot use DDR3 at all...  If you're using CORE OPP50 then you can only use MPU OPP50 and MPU OPP100 as shown in Table 5-8 "Valid Combinations of VDD_CORE and VDD_MPU OPPs for ZCZ Package with Device Revision Code "A" or Newer".