5 ms·

Xfinity XB3 hardware mod: Disable WiFi and save 2 watts

87 points by p1mrx 2y ago

don-code 2y ago
While I doubt they'd find it - the SOP for issues with these modems must just be to replace them with a new one - something tells me Comcast wouldn't look kindly on physically modifying rental equipment.
- p1mrx 2y ago
  I'm not sure how NOW handles replacements, but the modem has a label saying "This is customer owned equipment and should not be collected or swapped by Comcast personnel, unless within warranty repair." The FAQ says "your NOW Internet Gateway comes with a 90-day warranty" so perhaps they'd care somewhat about mods within the first 90 days.
easton 2y ago
I’d note that (outside of Comcast possibly being mad at you breaking the modem), sometimes they push a bad update and you need to reset the modem, and last time I did that I needed to step through the initial setup on the WiFi network before activating bridge mode. So if the wifi hardware is broken you might need to jump through hoops to get through that setup (or swap the modem).
- p1mrx 2y ago
  I tried a factory reset, and was able to configure bridge mode via ethernet.
rasz 2y ago
In 2014 Liberty Global decided to offer UPC Wifi Free - free roaming wifi on all cable modems they manage. Your own modem would advertise HotSpot and share your own cable connection. In theory you could opt out, in practice when I tried it just meant removing my login credentials while my box still shared and disabling Wifi locally would bring it back after a while. Thankfully Cisco EPC3925 uses BCM43225 mpcie Wifi card and unplugging it removes all mentions of wireless functionality from Setup, problem solved.
- technofiend 2y ago
  This is exactly what Comcast does with their Xfinity service if you use one of their devices.
  - heavyset_go 2y ago
    It's something you can disable with a toggle.
johnklos 2y ago
It amazes me that devices with Intel Puma chipsets are still sold new and are still in use in 2025. That's another story, though. The number of wifi networks that're running around us has gotten so crazy that it's no wonder we all need wifi-6 to even get reasonable speeds. I'm the kind of person who goes around and disables wifi absolutely everywhere possible, so this is good to know, but what'd be even better is if devices stopped running wifi networks behind our backs. Sigh.
- technofiend 2y ago
  You really want 6e or 7 these days so you can shift to 6GHz. There are many more channels available, adoption is limited so there's less congestion and the signal attenuates more quickly and has higher free-space path loss as well. Sounds like you may already know all that but for anyone thinking about investing in an upgrade, the reasons listed above are why you'd want to invest in the latest tech.
  - sightbroke 2y ago
    Why would faster signal attenuation be a good thing?
    - Cerium 2y ago
      Don't need to fight for spectrum with the neighbors.
    - diamondlovesyou 2y ago
      Less area means less sources of interference for others (this property is also true in the other direction). So the attenuation reduces the signal area, and stronger attenuation lets the transmitter be "strong" in the house without the downsides in congested areas.
    - heavyset_go 2y ago
      Imagine sharing the spectrum in an apartment in a high population density city.
metaphor 2y ago
Uhhh, sanity check: If you lived in a state like Hawaii where the cost of residential electricity approaches outrageous territory (i.e. ~$0.50/kWh), then you'd be hard pressed to save $1 per month trimming -2.4W nominal consumption with this hack. Perhaps I'm just naive, but this struck me as the buried lede: > ...but even in bridge mode, the gateway broadcasts several hidden SSIDs with no option to disable the radios.
- the_svd_doctor 2y ago
  In SF Bay Area my PG&E rate is also close to 0.5$/kWh…
  - metaphor 2y ago
    My condolences...looks[1] painful. [1] https://www.pge.com/assets/pge/docs/account/rate-plans/residential-electric-rate-plan-pricing.pdf https://www.pge.com/assets/pge/docs/account/rate-plans/resid...
- p1mrx 2y ago
  The cheaper service more than offsets the cost of electricity, I just prefer to use an OpenWrt router, and it bothered me to burn more energy on a worse modem that spews WiFi for no apparent reason. If xfinitywifi were on the list, I would at least understand what it's for.
- maccard 2y ago
  There’s 13 million households in California. Theoretically, if every household saved 2 watts with this change it would remove a small gas power plant from the grid. It’s nothing for one household but this sort of efficiency at scale makes a difference.
  - metaphor 2y ago
    That's all motherhood and apple pie, but it's a red herring with no basis in pragmatic reality (i.e. not how the calculus of utility-scale power generation industrial planning/ops works), and wholesale disingenuous to posit that even a residual percentage of those households---say, asymptotic to the proportional marketshare of Firefox users in the state as a comparatively low friction proxy aspirational target---would even attempt this hack...to say nothing of its trade-offs or implied liabilities to the end user iff successfully implemented...or how Comcast would be incentivized if adoption achieved a critical mass that made the hack observable (either technically or monetarily) on their end. Not to discredit the author for sharing the insight, but the hard sell of saving 2W consumption simply isn't a prime mover here. If anything, mitigation of implicit side channel RF interference when the hack is paired with a OpenWrt router (as the author apparently intended) makes a lot more compelling sense...but now we're talking about bootstrapping an additional appliance into the setup, rendering contextual discussion of power savings objectively moot.
quailfarmer 2y ago
Yes, this is great! They gave me a similar model under the same deal, and it had a fan that would ramp up and down all day and night.
wpm 2y ago
Every ISP should be required upon request to provide the necessary hardware to provide a single IP address on a single copper cable. If some dumb bozo wants to get the ISP deluxe package of gateway/router/DNS sniffer/shit-tier WiFi AP all rolled into one box, fine. The opt out should be as simple as “I have my own equipment, I understand that any support call with you will stop after a public IP is found to be working on premise, now get the hell out of my way thank you”
- jchw 2y ago
  The normal Comcast plans do let you do that, this is some weird special plan. You can hook up a standard DOCSIS modem and then DHCP lease an IP. There are a lot of technically-proficient people who refuse to do this anymore. I guess it is a non-zero amount of work, but it really, really isn't that much. The direction we're headed in is pretty obvious: some day, sooner rather than later, the era of customers being able to use their own cable modems for DOCSIS internet will slowly end, as the people who bother become more and more in the minority.
  - iforgotpassword 2y ago
    This was the norm in Germany for a while. Then we got a law ("Routerfreiheit") that forces ISPs to allow you to use and modem/router you want. Before that you couldn't do it with DOCSIS, but it kinda worked with DSL, if you could somehow get the PPPoE credentials. Nowadays they have to provide PPPoE and voip credentials, and cable providers need to provide a service where you give them the Mac of your own modem and then it gets tied to your contract.
  - barnas2 2y ago
    Cox also lets you do this, although they'll straight up lie to you on the phone. The rep very confidently told me I could not use my own equipment, and was required to use theirs, despite their website claiming otherwise.
    - ryandrake 2y ago
      The customer support reps might just be poorly trained (yet confident), and not lying. Calling it "lying" requires there to be an intent to deceive.

87 points by p1mrx 2y ago

While I doubt they'd find it - the SOP for issues with these modems must just be to replace them with a new one - something tells me Comcast wouldn't look kindly on physically modifying rental equipment.

p1mrx 2y ago
I'm not sure how NOW handles replacements, but the modem has a label saying "This is customer owned equipment and should not be collected or swapped by Comcast personnel, unless within warranty repair." The FAQ says "your NOW Internet Gateway comes with a 90-day warranty" so perhaps they'd care somewhat about mods within the first 90 days.

easton 2y ago

I’d note that (outside of Comcast possibly being mad at you breaking the modem), sometimes they push a bad update and you need to reset the modem, and last time I did that I needed to step through the initial setup on the WiFi network before activating bridge mode. So if the wifi hardware is broken you might need to jump through hoops to get through that setup (or swap the modem).

p1mrx 2y ago
I tried a factory reset, and was able to configure bridge mode via ethernet.

rasz 2y ago

In 2014 Liberty Global decided to offer UPC Wifi Free - free roaming wifi on all cable modems they manage. Your own modem would advertise HotSpot and share your own cable connection. In theory you could opt out, in practice when I tried it just meant removing my login credentials while my box still shared and disabling Wifi locally would bring it back after a while. Thankfully Cisco EPC3925 uses BCM43225 mpcie Wifi card and unplugging it removes all mentions of wireless functionality from Setup, problem solved.

technofiend 2y ago
This is exactly what Comcast does with their Xfinity service if you use one of their devices.
- heavyset_go 2y ago
  It's something you can disable with a toggle.

johnklos 2y ago

It amazes me that devices with Intel Puma chipsets are still sold new and are still in use in 2025. That's another story, though. The number of wifi networks that're running around us has gotten so crazy that it's no wonder we all need wifi-6 to even get reasonable speeds. I'm the kind of person who goes around and disables wifi absolutely everywhere possible, so this is good to know, but what'd be even better is if devices stopped running wifi networks behind our backs. Sigh.

technofiend 2y ago
You really want 6e or 7 these days so you can shift to 6GHz. There are many more channels available, adoption is limited so there's less congestion and the signal attenuates more quickly and has higher free-space path loss as well. Sounds like you may already know all that but for anyone thinking about investing in an upgrade, the reasons listed above are why you'd want to invest in the latest tech.
- sightbroke 2y ago
  Why would faster signal attenuation be a good thing?
  - Cerium 2y ago
    Don't need to fight for spectrum with the neighbors.
  - diamondlovesyou 2y ago
    Less area means less sources of interference for others (this property is also true in the other direction). So the attenuation reduces the signal area, and stronger attenuation lets the transmitter be "strong" in the house without the downsides in congested areas.
  - heavyset_go 2y ago
    Imagine sharing the spectrum in an apartment in a high population density city.

metaphor 2y ago

Uhhh, sanity check: If you lived in a state like Hawaii where the cost of residential electricity approaches outrageous territory (i.e. ~$0.50/kWh), then you'd be hard pressed to save $1 per month trimming -2.4W nominal consumption with this hack. Perhaps I'm just naive, but this struck me as the buried lede: > ...but even in bridge mode, the gateway broadcasts several hidden SSIDs with no option to disable the radios.

the_svd_doctor 2y ago
In SF Bay Area my PG&E rate is also close to 0.5$/kWh…
- metaphor 2y ago
  My condolences...looks[1] painful. [1] https://www.pge.com/assets/pge/docs/account/rate-plans/residential-electric-rate-plan-pricing.pdf https://www.pge.com/assets/pge/docs/account/rate-plans/resid...
p1mrx 2y ago
The cheaper service more than offsets the cost of electricity, I just prefer to use an OpenWrt router, and it bothered me to burn more energy on a worse modem that spews WiFi for no apparent reason. If xfinitywifi were on the list, I would at least understand what it's for.
maccard 2y ago
There’s 13 million households in California. Theoretically, if every household saved 2 watts with this change it would remove a small gas power plant from the grid. It’s nothing for one household but this sort of efficiency at scale makes a difference.
- metaphor 2y ago
  That's all motherhood and apple pie, but it's a red herring with no basis in pragmatic reality (i.e. not how the calculus of utility-scale power generation industrial planning/ops works), and wholesale disingenuous to posit that even a residual percentage of those households---say, asymptotic to the proportional marketshare of Firefox users in the state as a comparatively low friction proxy aspirational target---would even attempt this hack...to say nothing of its trade-offs or implied liabilities to the end user iff successfully implemented...or how Comcast would be incentivized if adoption achieved a critical mass that made the hack observable (either technically or monetarily) on their end. Not to discredit the author for sharing the insight, but the hard sell of saving 2W consumption simply isn't a prime mover here. If anything, mitigation of implicit side channel RF interference when the hack is paired with a OpenWrt router (as the author apparently intended) makes a lot more compelling sense...but now we're talking about bootstrapping an additional appliance into the setup, rendering contextual discussion of power savings objectively moot.

quailfarmer 2y ago

Yes, this is great! They gave me a similar model under the same deal, and it had a fan that would ramp up and down all day and night.

wpm 2y ago

Every ISP should be required upon request to provide the necessary hardware to provide a single IP address on a single copper cable. If some dumb bozo wants to get the ISP deluxe package of gateway/router/DNS sniffer/shit-tier WiFi AP all rolled into one box, fine. The opt out should be as simple as “I have my own equipment, I understand that any support call with you will stop after a public IP is found to be working on premise, now get the hell out of my way thank you”

jchw 2y ago
The normal Comcast plans do let you do that, this is some weird special plan. You can hook up a standard DOCSIS modem and then DHCP lease an IP. There are a lot of technically-proficient people who refuse to do this anymore. I guess it is a non-zero amount of work, but it really, really isn't that much. The direction we're headed in is pretty obvious: some day, sooner rather than later, the era of customers being able to use their own cable modems for DOCSIS internet will slowly end, as the people who bother become more and more in the minority.
- iforgotpassword 2y ago
  This was the norm in Germany for a while. Then we got a law ("Routerfreiheit") that forces ISPs to allow you to use and modem/router you want. Before that you couldn't do it with DOCSIS, but it kinda worked with DSL, if you could somehow get the PPPoE credentials. Nowadays they have to provide PPPoE and voip credentials, and cable providers need to provide a service where you give them the Mac of your own modem and then it gets tied to your contract.
- barnas2 2y ago
  Cox also lets you do this, although they'll straight up lie to you on the phone. The rep very confidently told me I could not use my own equipment, and was required to use theirs, despite their website claiming otherwise.
  - ryandrake 2y ago
    The customer support reps might just be poorly trained (yet confident), and not lying. Calling it "lying" requires there to be an intent to deceive.