Reducing power consumption on lantiq devices with 34Kc CPU

#1

Hi folks,

I began to like the lantiq devices with the 34Kc CPU. However, one thing that I don't like yet is the power consumption. After booting up, the devices consumes around 5-6W in idle, while it only consumes 2-3W when in bootloader.

Are there any tunables that can be modified to get the power consumption down (at the cost of performance)? And yes, i've seen the thread about overclocking but I'm not sure if this would work for lantiq devices as well.

Many thanks in advance!

#2

Overclocking often raises the power consumption, between more clocks per second, and often needing to raise the voltage to be able to "charge" the internals faster to be able to get them to switch at the higher clock rate.

20 dBm is 0.1 W of RF out, 30 dBm is 1 W. If you're using the wireless heavily, seeing an increase in power consumption over the bootloader isn't out of the ordinary.

Having to run on backup power here more often than I care, lower power consumption is something I do pay attention to. My Archer C7s run around 1-2W during boot, 3-4 W at idle, and a tad higher with heavy wireless activity. Assuming you trust a "Kill-A-Watt" to be able to measure with any accuracy at those levels.

Does your switch allow you to enable "energy efficient" Ethernet?

Is your power supply ("wall wart") efficiency Class VI or better? That might gain you 20% or so, depending on the efficiency of your supply and if it is oversized or not.

I'm assuming you don't have any USB devices. They can consume significant power compared to a Watt.

Turning off the LEDs might gain you a fraction of a Watt as well.

Archer c7 - 5 ghz channel - power consumption heat
#3

Thank you! And sure, while overclocking raises power consumption in theory the same measures could be used to reduce clock/voltage and thus power consumption.

In my case, only 1 port of the switch is used and 1 is used if connected. I guess I could disable the two others. Radio is not used and thus rutned off already. I use the vendor-supplied power adapter, so yes, maybe this could be a way to reduce power.

I thought about using one of these devices only as VLAN switch (disabling modem, radio, usb etc.) but to do that I would need to bring down the power consumption way more down.

#4

Hey there!
I don't know about the soc's you are working with, but if they have dsl capabilities, try disabling the dsl daemon (dsl_control?). I remember lantiq danube chips with adsl modems integrated,ran very hot and subsequently consuming lots of power.

1 Like
#5

Although I need the modem I would be interested in how much power it draws and how much power the switch consumes. However, I didn't find the right commands to turn off any of them. service dsl_control stop doesn't seem to do the trick, at least no change regarding power consumption.

After commenting out the corresponding entries in /etc/modules.d, I got the following measures in idle (with 1x lan cable connected):

  • all enabled: 6.1W
  • wifi disabled, adsl enabled, usb enabled: 5.7W
  • wifi enabled, adsl disabled, usb enabled: 3.8W
  • wifi disabled, adsl disabled, usb enabled: 3.4W
  • wifi disabled, adsl disabled, usb disabled: 3.4W

So indeed, it seems that the dsl modem is the power-eater here as you suspected, @Ntalton. I didn't try disabling the switch yet since I already closed the case, but I would be interested on the difference here as well. I assume the switch might consume another 1W or so in idle.

#6

I wouldn't disable the switch. How would you connect anything to the router and what is the purpose of the the router without the switch?

#7

@rj-45 I am using the device only as modem, see also:

I thought about using an external USB NIC if it would draw less power than the integrated switch as I only need one LAN port anyways.