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Few benefits To Overclocking the CPU on the Pi4?



  • I've had my Pi4 overclocked for a while now and I've come to the conclusion that overclocking the CPU may not be of much benefit. I think only Crash Team Racing on the PS1 is benefiting at all.

    What are your experiences/thoughts about this. To be clear this is just about overclocking the CPU, not the GPU. Overclocking the GPU seems to be beneficial for a couple of higher end systems such as the N64, Dreamcast & PSP.

    I'm running a weekly build of Retropie updated to 4.5.18 on a 4GB Pi4B. My current overclocking settings are:

    over_voltage=6
    hdmi_enable_4kp60=1
    arm_freq=2000
    core_freq=550
    v3d_freq=800


  • Global Moderator

    given that cpu very was rarely a bottleneck on rpi3 (and pi3+), i expect a similar situation on pi4. if you check cpu usage (via shh + top) you'll see that most emulation barely puts a dent in a single CPU core. n64 is around ~50-60% for a pi3, for example. similar numbers for psx.

    very rarely do pi overclockers seem to be that interested in actually benchmarking the improvements, or identifying bottlenecks, just overclocking things until they crash. so, good for you! :)



  • @George-Spiggott More cpu power will always help with features like readahead if you use them. Also, how does a game with higher cpu requirements (let's say hvysmsh ?) fare on FBNeo/MAME with and without OC on pi4 ?



  • @barbudreadmon I'm unfamiliar with that game. Rad Mobile (System 32/MAME 2010) ran slow on my Pi3b but runs fine on my pi4. I'll try that without the overclocking.

    Any PS1 games on PSXReARMed that need the dynarec turned off like CTR does will also benefit from overclocking, especially with the hi res hack turned on.



  • @George-Spiggott said in Few benefits To Overclocking the CPU on the Pi4?:

    I'm unfamiliar with that game

    It's kind of an improved version of Soccer Brawl, it's pretty fun.



  • @barbudreadmon said in Few benefits To Overclocking the CPU on the Pi4?:

    @George-Spiggott More cpu power will always help with features like readahead if you use them.

    How would you go about measuring how much readahead you are getting? Is more always better or is there a practical limit?



  • @George-Spiggott I know of a measuring method for input lag, it uses a keyboard though : press P to pause a game, press and hold a game button (some action you'll easily notice), then press K repeatedly to run 1 frame at a time until you see your character doing the action. The number of times you pressed K, minus 1, is the input lag.



  • @George-Spiggott said in Few benefits To Overclocking the CPU on the Pi4?:

    I'll try that without the overclocking.

    How did your tests go ?



  • My pi 4 definitely boots faster with the CPU overclocked and installing emulators from source is also faster. Ill have to run some tests but I suspect that dosbox, mame, and other high CPU usage emulators also benefit as well.

    Ive been testing ppsspp performance with overclocking and without and its very hard to get a baseline. Im getting inconsistent results. If I check the fps on one game then reboot that game sometimes I get a different result even though its the same exact save state.

    Edit:
    However, running Killer Instinct on mame2003, overclocking the CPU gives a dramatic fps boost. With stock 1500mhz CPU Im getting roughly 40-50fps during the first stage, when overclocked to 2050mhz its between 55-60fps. So to say that there is no benefit is not true but it just may not benefit everyone depending on which game/system you are running.



  • Nobody is making a case for no benefits. What benefits there are will certainly be dependant on your collection. I didn't even know Killer Instinct ran on MAME 2003, thanks.

    I droppped from a 2,000ghz to standard CPU settings. I tried Rad Mobile and Power Drift on MAME 2010. Apart from a few of the Namco 3D fighting games I have (which never run at full speed) they are the most demanding arcade games I possess.

    Rad Mobile goes from 60 to 55fps and loses a lot of the sound. Power Drift actually improved. It kept 60fps but there were no breaks in the sound.

    Crash Team Racing (dynarec off, enhanced graphics on) doesn't seem to play any differently. The sound is still patchy as it was overclocked. I will go back and check this overclocked, it may have improved in an update.

    [EDIT] I forgot CTR was running with Frameskip 1. Frameskip seems to be more beneficial than the overclock for CTR. Rad Mobile had frameskip 2 set in both tests.



  • From the games in my collection I have found that setting Audio Latency (ms) to 512 has almost the same effect as overclocking.

    I have noticed that my pi definitely takes longer to boot.

    Rad Mobile (MAME 2010) still runs at a lower FPS but it isn't actually that noticeable (if at all) while playing and the higher audio latency stops the audio from cutting out.

    Crash Team Racing runs well and only slowed down intermittently with graphical enhancement on and dynarec turned off but setting frameskip (with or without the overclock) prevents the sound cutting out.

    I have tried to run Killer Instinct but I can't get my copy to run. I may be putting the .CHD file in the wrong place.



  • @dankcushions said in Few benefits To Overclocking the CPU on the Pi4?:

    given that cpu very was rarely a bottleneck on rpi3 (and pi3+), i expect a similar situation on pi4. if you check cpu usage (via shh + top) you'll see that most emulation barely puts a dent in a single CPU core. n64 is around ~50-60% for a pi3, for example. similar numbers for psx.

    I see that top gives a result of over 120% for PPSSPP while playing Tomb Raider Anniversary (One of the more demanding PSP games). Would CPU showing at over 100% provide a useful guide to cores that would benefit from overclocking the CPU?


  • Global Moderator

    @George-Spiggott said in Few benefits To Overclocking the CPU on the Pi4?:

    @dankcushions said in Few benefits To Overclocking the CPU on the Pi4?:

    given that cpu very was rarely a bottleneck on rpi3 (and pi3+), i expect a similar situation on pi4. if you check cpu usage (via shh + top) you'll see that most emulation barely puts a dent in a single CPU core. n64 is around ~50-60% for a pi3, for example. similar numbers for psx.

    I see that top gives a result of over 120% for PPSSPP while playing Tomb Raider Anniversary (One of the more demanding PSP games). Would CPU showing at over 100% provide a useful guide to cores that would benefit from overclocking the CPU?

    it depends, as that could just mean 4 cores are at 30%, for example. overclocking CPU should only help if at least one core is at 100% (or certain bandwidth issues, and other situations). the only way to be sure is to benchmark that application.



  • I just tried a test run with the CPU overclocked (CPU 2000, GPU 850). All I seemed to get for my trouble was some graphical glitching. I could't detect any noticeable change in speed.

    More testing required at some point.



  • My recent testing of N64 performance shows something similar, i.e. overclocking not helping much. Doesn't matter if it's CPU or GPU that's overclocked, at least for the games I tested (SotE and OOT). In this case it might be caused by a highly irregular load, i.e. varying processing needs on a frame-to-frame basis. Most frames seem to easily be rendered within the 16.67 ms interval necessary for 60 FPS. However, some frames seem to take a disproportionate amount of time, i.e. 20-40 ms. The result is high average frame rate, but with large frame time deviations. This means that even though the average frame rate can be over 100 FPS, a small number of frames is far from being able to complete on time. This leads to stuttering (most obviously in the audio). It also means that overclocking 20-30 % might not help much, since most frames are already completed on time and those that aren't are so far from being completed on time that an overclock is not enough. Well, at least that's a theory I have after some testing.

    See discussion issue I created after mucking around with this for a few hours: https://github.com/libretro/mupen64plus-libretro-nx/issues/177

    Please note that this doesn't mean that overclocking won't help in many cases. The CPU and GPU does execute faster when overclocked, but the improvement will depend on the characteristics of the code being run and the particular bottleneck experienced.



  • I've got SotE to run almost completely without audio stuttering with the GPU overclocked to 850. Core overclock to 700 gets you close (Core will not overclock above 700 even if set higher). V3D and CPU at any setting seem to have no effect whatsoever.

    I find that the audio stutter occurs most (with GPU @ 850 and Audio Latency (ms) set to 512) when the Outrider flies towards Hoth in the intro. It also occurs when the AT-ST is show on the mission debrief.

    Over on the Dreamcast with the same overclock/audio settings I have got Soul Calibre to run on Lr-Flycast in 960p with widescreen hack turned on and no audio skipping in game. There is rather a lot on the intro screens though. I also think that I have Soul Edge running at almost full speed on MAME 2010. Again there is audio skipping but the counter states that the game is running at 59FPS.

    I have re-added an overclock of 1750 on the CPU just because it makes boot up and menus in Retropie run a little smoother.



  • @George-Spiggott said in Few benefits To Overclocking the CPU on the Pi4?:

    I've got SotE to run almost completely without audio stuttering with the GPU overclocked to 850. Core overclock to 700 gets you close (Core will not overclock above 700 even if set higher).

    Are you on a pi 4? Last I heard core_freq was limited to 500mhz or 550mhz if you enabled 4k60 mode.



  • @quicksilver That was my understanding but 'vcgencmd get_config core_freq' reports 700 if I set 'core_freq=700' in my config.txt

    I get a noticeable speed increase if I set core_freq to this so I don't think it is a misreading.



  • @George-Spiggott I believe that's just reporting what value you set in the config.txt. can you try vcgencmd measure_clock core. Preferably while running a game so that your governor doesn't downclock the GPU while you are testing.



  • @quicksilver said in Few benefits To Overclocking the CPU on the Pi4?:

    Are you on a pi 4? Last I heard core_freq was limited to 500mhz or 550mhz if you enabled 4k60 mode.

    I can confirm this. I've tried overclocking the core and it stays at 500 MHz. It should also be mentioned that gpu_freq is an umbrella setting that sets core_freq, h264_freq, isp_freq, v3d_freq and hevc_freq together. This would explain why setting v3d_freq separately like @George-Spiggott mentioned doesn't improve performance, since it's already overclocked.



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