Radxa X4 C-State: even Package C2 is not possible?

X Series X4
1

Hi,

I’ve enabled C-states in the X4 BIOS, but checking with powertop, all the Package C2-C10 C-States are 0%. I tried with the V002 Testing BIOS and enabled ASPM everywhere but still no luck.

I know that for N100, the power consumption is pretty low, deeper C-States are not as important as desktop-level CPU platforms, but it’s still a better-to-have.

Also, the GPU is in Power On state at 100% with RC6 0%, not sure if that is related to the C-state issue above.

2

Running a X4 with FreeBSD, not really tuned the BIOS and what to say, C3 without any problems:

root@freebsd:~ # uname -a
FreeBSD freebsd 14.3-RELEASE FreeBSD 14.3-RELEASE releng/14.3-n271432-8c9ce319fef7 GENERIC amd64
root@freebsd:~ # sysctl -a | grep -e 'dev\.cpu\..\.cx_'
dev.cpu.3.cx_method: C1/mwait/hwc C2/mwait/hwc C3/mwait/hwc
dev.cpu.3.cx_usage_counters: 2287 6105 14056
dev.cpu.3.cx_usage: 10.18% 27.19% 62.61% last 86us
dev.cpu.3.cx_lowest: C6
dev.cpu.3.cx_supported: C1/1/1 C2/2/127 C3/3/1048
dev.cpu.2.cx_method: C1/mwait/hwc C2/mwait/hwc C3/mwait/hwc
dev.cpu.2.cx_usage_counters: 2522 7206 20905
dev.cpu.2.cx_usage: 8.23% 23.52% 68.24% last 2281us
dev.cpu.2.cx_lowest: C6
dev.cpu.2.cx_supported: C1/1/1 C2/2/127 C3/3/1048
dev.cpu.1.cx_method: C1/mwait/hwc C2/mwait/hwc C3/mwait/hwc
dev.cpu.1.cx_usage_counters: 2277 5886 12632
dev.cpu.1.cx_usage: 10.94% 28.30% 60.74% last 232us
dev.cpu.1.cx_lowest: C6
dev.cpu.1.cx_supported: C1/1/1 C2/2/127 C3/3/1048
dev.cpu.0.cx_method: C1/mwait/hwc C2/mwait/hwc C3/mwait/hwc
dev.cpu.0.cx_usage_counters: 16935 403730 0
dev.cpu.0.cx_usage: 4.02% 95.97% 0.00% last 44us
dev.cpu.0.cx_lowest: C6
dev.cpu.0.cx_supported: C1/1/1 C2/2/127 C3/3/1048

Only core 0 does not go deeper than C2, but something always runs, doesn’t it?

best

3

Thanks for the info! Could you please reveal which BIOS version are you running?

4

Its the stock BIOS, early production model, so I’d guess V001. Can’t reboot and check the BIOS right now, but here is what the BIOS itself claims:

root@freebsd:~ # dmidecode
[...]
Handle 0x0000, DMI type 0, 26 bytes
BIOS Information
	Vendor: American Megatrends International, LLC.
	Version: 5.27
	Release Date: 08/19/2024
[...]

best

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5

I guess yours is also V002, but it doesn’t matter. For me C-states works as well now - I was running GRML via netboot and could NOT reach PC3, but with a proper OS installation (Debian 13) on the eMMC, the X4 could reach PC3.

Then with BIOS tunings (ASPM enabled everywhere), it could reach PC6. I’m satisfied already and would not pursue deeper C-states. Now the board consumes only 2 Watts.

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