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10gig copper ethernet is hotter and more power hungry than the equivalent SFP+. Maybe you’re comparing a faster SFP port to a slower ethernet port? 2 to 5 watt

10gig copper ethernet is hotter and more power hungry than the equivalent SFP+. Maybe you’re comparing a faster SFP port to a slower ethernet port? 2 to 5 watts for ethernet, less than 1 watt for SFP+.[0] [0]: https://community.fs.com/blog/10gbase-t-vs-sfp-which-one-is-the-best-option-for-10gbe-data-center-cabling.html https://community.fs.com/blog/10gbase-t-vs-sfp-which-one-is-... I really wish SFP+ and SFP28 would be more common in high end desktop motherboards. They’re more efficient and just better, and they can be adapted to plain old ethernet if needed (at a power penalty imposed by switching away from fiber).

mmastrac 4y ago
Interesting... my experience has been the opposite, but I will admit I am not a network engineer. I've burned my fingers on SFP modules a few times, however. Do you think that power requirements are different because SFP often uses direct-attach copper? I'm honestly curious to reconcile my experience with other, more experience persons' reality here.
- coder543 4y ago
  I believe both DAC and fiber draw about the same power, but DAC obviously has very limited cable lengths. I’m not entirely sure why regular ethernet draws more power, I just know this is a fairly consistent thing wherever I look. Handling the SFP module itself will more directly expose you to the heat than an integrated ethernet port, so maybe that’s the difference.
  - mmastrac 4y ago
    > Handling the SFP module itself will more directly expose you to the heat than an integrated ethernet port, so maybe that’s the difference. This would explain a lot, TBH. Thanks for the productive discussion -- it helped me realize a few gaps in my knowledge
  - washadjeffmad 4y ago
    Our old RJ45 transceivers always caused the cards to run at the maximum wattage required for the longest supported run of cable. I don't recall if it was a quirk of the spec or a lack of sensing.
- justsomehnguy 4y ago
  DAC transcievers are always hotter than a fiber ones, easily tested by handling them (for a comparable speeds) in one chassis. And on the minor note - external SAS connectors (6/12gbps) are more then just warm, too. My own experience, YMMW.
sschueller 4y ago
Agreed, especially frustrating with new motherboards having just 3 full PCIe slots and 2 being blocked by the GPU. Also the crap with vendor locking SFP slots by Dell and Cisco especially. At least Intel cards are quite universal. USB-C to SFP+ is also way to expensive and you can't do SFP28 on USB 3 speeds.

mmastrac 4y ago

Interesting... my experience has been the opposite, but I will admit I am not a network engineer. I've burned my fingers on SFP modules a few times, however. Do you think that power requirements are different because SFP often uses direct-attach copper? I'm honestly curious to reconcile my experience with other, more experience persons' reality here.

coder543 4y ago
I believe both DAC and fiber draw about the same power, but DAC obviously has very limited cable lengths. I’m not entirely sure why regular ethernet draws more power, I just know this is a fairly consistent thing wherever I look. Handling the SFP module itself will more directly expose you to the heat than an integrated ethernet port, so maybe that’s the difference.
- mmastrac 4y ago
  > Handling the SFP module itself will more directly expose you to the heat than an integrated ethernet port, so maybe that’s the difference. This would explain a lot, TBH. Thanks for the productive discussion -- it helped me realize a few gaps in my knowledge
- washadjeffmad 4y ago
  Our old RJ45 transceivers always caused the cards to run at the maximum wattage required for the longest supported run of cable. I don't recall if it was a quirk of the spec or a lack of sensing.
justsomehnguy 4y ago
DAC transcievers are always hotter than a fiber ones, easily tested by handling them (for a comparable speeds) in one chassis. And on the minor note - external SAS connectors (6/12gbps) are more then just warm, too. My own experience, YMMW.

sschueller 4y ago

Agreed, especially frustrating with new motherboards having just 3 full PCIe slots and 2 being blocked by the GPU. Also the crap with vendor locking SFP slots by Dell and Cisco especially. At least Intel cards are quite universal. USB-C to SFP+ is also way to expensive and you can't do SFP28 on USB 3 speeds.