Few benefits To Overclocking the CPU on the Pi4?
-
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?
-
@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.
-
@quicksilver It does indeed change when an emulator is launched from 'frequency(1)=275273440' to 'frequency(1)=550006336'. core_freq setting was 750 for this test.
@Brunnis I was using V3D on its own without the GPU overclock and with CORE overclocked to 550. The full settings I was using are in my OP.
-
@George-Spiggott said in Few benefits To Overclocking the CPU on the Pi4?:
@Brunnis I was using V3D on its own without the GPU overclock and with CORE overclocked to 550. The full settings I was using are in my OP.
I understand, but I was refering to this:
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.
This suggested that you set gpu_freq to 850 MHz, which would be equal to (disregarding the video/ISP block effects):
v3d_freq = 850
core_freq is already at 550 MHz, since you have set hdmi_enable_4kp60=1, so the gpu_freq doesn't do anything more there. If v3d_freq doesn't have any effect on its own, using gpu_freq shouldn't either.
-
@Brunnis Perhaps I was unclear. I am only using GPU. I have used Core and V3D in conjunction.
I'll try swapping GPU for V3D to see if there is any change.
-
@George-Spiggott said in Few benefits To Overclocking the CPU on the Pi4?:
Perhaps I was unclear. I am only using GPU. I have used Core and V3D in conjunction.
On the pi 4 core freq is no longer controller by GPU freq. So for our purposes, GPU/v3d freq are synonymous since the other blocks of the GPU are irrelevant/unused in emulation.
-
@quicksilver Yes I have now set my V3D to 850. I'm not sure why V3D was not previously giving me these benefits.
-
So, not wanting to necro this thread, but I wanted to raise a specific question from my own tests here.
I have recently added the 4k60 flag on top of the previous overclock I had - I was running the arm_freq at 2100 but it ended up being a bit unstable, so I'm not testing 2050. I know that 2000 was perfectly fine as that's how I had it for the last months, but I'd like to squeeze as much as possible out of it for the CAVE shooters on lr-mame2015/16, which run at 85%-95% speed on average.
Now, what I have observed in my monitoring script, at arm_freq 2050 plus the 4k60 flag is the following discrepancy, which I was wondering if a) was known, b) anyone else had noticed, and c) anyone would be able to explain.
I'm retrieving, in runtime, CPU speed via:
cpuSpeed0=$(cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq)and ARM Frequency via:
armFreq0=$(vcgencmd measure_clock arm)and while without the 4k60 flag, they pretty much mapped 1:1, with the 4k60 flag I'm noticing them to be different:
CPU Speed: 2194 MHz
ARM Freq: 2050MHzI had read that the 4k60 flag is supposed to increase the clock by ~10%, but with these two being different, what am I really observing? Is the Pi running at almost 2200MHz or is 2050MHz the actual speed it's running, and so I should just ignore that reading and perhaps even remove the 4k60 flag as I'm not running this on a 4k monitor? When I was running arm_freq=2100, the CPU Speed would report close to 2300 MHz even.
I'd love your (more informed) thoughts on this, as I'm sure you have been looking into overclocking for longer than I have. :)
Thanks, and have a great weekend!
-
@pjft said in Few benefits To Overclocking the CPU on the Pi4?:
I had read that the 4k60 flag is supposed to increase the clock by ~10%
The 4k60 flag increases the GPU core freq from 500mhz to 550mhz. It shouldn't affect the CPU freq. I have gotten weird readings in the past where it reported much higher CPU frequencies than is possible. Im not sure what causes it, but I believe it's a false report.
Contributions to the project are always appreciated, so if you would like to support us with a donation you can do so here.
Hosting provided by Mythic-Beasts. See the Hosting Information page for more information.