Few benefits To Overclocking the CPU on the Pi4?

George Spiggott

@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.

quicksilver

@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.

Brunnis

@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.

George Spiggott

@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.

Brunnis

@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.

George Spiggott

@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.

quicksilver

@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.

George Spiggott

@quicksilver Yes I have now set my V3D to 850. I'm not sure why V3D was not previously giving me these benefits.

pjft

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: 2050MHz

I 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!

quicksilver

@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.