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Couple of questions relating to the sdram_freq setting in regards to overclocking



  • I am running what I consider to be a fairly conservative and stable overclock on my pi 3b+, with these settings:

    arm_freq=1500
    gpu_freq=500
    core_freq=500
    sdram_freq=500
    sdram_schmoo=0x02000020
    over_voltage=6
    sdram_over_voltage=2

    I am looking to try pushing the sdram_freq higher, perhaps to 550 to start, as I have heard this can give some good real world benefits to various emulation. I am wondering two things though:

    1. Is there a relationship between that setting and any other setting? Would it be necessary or beneficial, for example, to raise the core_freq in tandem with that to 550?

    2. What is the risk of failure in overclocking that setting? Overheating and lockup as with cpu only overclock, or is there an increased chance at that frequency of 550 or generally to slowly or instantly corrupt my microsd or something else terrible, or am I generally good if it results in stable temps and no lockups?

    Thanks!



  • @RC_Cola - I haven't done much with the 3+ but plenty with the 3. I think you should be able to safely bump sdram_freq to 550 without issue, possibly 575 but I would redo your stress tests after tweaking any overclock settings. I found I could push that setting pretty hard and keep a stable overclock. In all my testing on 3 I've easily was able to reach 550.

    The setting you might find challenging is the v3d_freq is very temperamental.

    The gpu_freq sets multiple parameters core_freq,h264_freq,isp_freq and v3d_freq. Basically core_freq is redundant in your config since you have them set to the same value. You may remove it but also if you feel more comfortable leave it in place.

    Also bumping core_freq has a small benefit for SDRAM on the 2/3 but I would only tweak and test one at a time.

    I've only had one time where I corrupted my SD card and I've locked up my Pi way more times than I can count overclocking but it's always good to have a backup image beforehand.

    If you have sufficient cooling you should be fine with overclocking and always stress test after any change, even what might seem small and insignificant.

    I think of overclocking as a whole separate area of setup on the Pi that's completely optional for maybe a 10% gain or so, maybe more in speed for a whole lot of testing. It has to be something you enjoy doing really but also it might make a difference on making that one game you can't live without run.

    I've never worried about shortening the life of the Pi overclocking. It outlives it's usefulness far beyond the next release cycle.

    You might find this thread helpful. The Overclock Wiki page has a lot of good information.

    Also this thread. It might sound strange but Quake III taxes the Pi in pretty much every way possible from CPU, graphics, memory, heat, a lot of heat. Your cooling solution will be thoroughly tested.

    There's a section on how to setup the game for play with all bots (8 or 9) and just let it run. I think the minimum burn I would do is about 2 hours. You're screen is just a blur of movement constantly.

    If your Pi locks even once, even hours in, I would call it unstable and re-tweak your settings. I even had a few times it dropped back to the game selection menu. I was able to let it run for hours without a single lockup or dropout once it was dialed in. You'll also see some tips on how to monitor the current speed and temps through Putty.

    There's always a risk of failure with overclocking. You may start with others values but don't call it gospel and do your own battery of stress tests. I think overclocking without thoroughly testing is like playing Russian roulette for potential crashes and corruption, it'll also alleviate concerns of is it stable and fast as possible. It just takes time as each Pi is slightly different and you're attempting to squeeze out every ounce of speed. In PC land it's a much more complicated art that has full blown competitions based solely on overclocking.



  • @riverstorm Thanks for a very comprehensive and helpful reply.



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