3 ms·
of course, but then you don't get the power advantages of copper SFP+ cabling. The 10gbase-t spec is the same spec either way, the reason it takes so much powe
by paulmd 5y ago
of course, but then you don't get the power advantages of copper SFP+ cabling. The 10gbase-t spec is the same spec either way, the reason it takes so much power is due to the length of the cables and the signal quality required of base-T cable, so it doesn't magically take less power because you run it through an adapter module.
(SFP has a limit of 7 meters for copper cables, I think it can go higher for active cables, but most people use fiber for longer runs)
If you just wanted to plug into a switch that was like 5 feet away, SFP copper cabling would actually reduce power a fair bit. Not really sure where fiber falls, but as far as copper, the problem is specifically the 10GBase-T leg, and if you include a 10GBase-T leg then you pay that power penalty regardless of whether it's via a native NIC or whether it's a SFP NIC with a module.
I do totally agree it would be a nifty idea though. It actually would bring down power for short connections, and a lot of laptop ethernet connections are "plug me into my desk switch" type use-cases anyway. Meanwhile, if you do want a longer connection, it doesn't limit your options because you can use a module.
But I suppose a lot of that has been subsumed into docks anyway. Thunderbolt 3 is absolutely fine for that hop to your dock. Related discussion but as a weirdo, I would actually rather have a more robust connector with longer distance support than Thunderbolt natively allows - if I could plug a cable and get 10 meters or so, that would solve some use-cases for me. Currently the only option is Optical Thunderbolt cables and everything I've heard is that they are absolutely flaky as hell and usually die after a year or so. I would love if I could use QSFP copper or something.
(my use-case is I want to have an external PCIe enclosure with the adapter for my Vive Wireless so the PC doesn't have to be in the room, but that would involve at least a 10 meter run for me realistically. Being able to run HDMI 2.1 over QSFP would also be neat because I could have my desktop run a 4K120 TV properly without having to have a dedicated HTPC there...)
Anyway back to SFP in laptops - you're right that it's pretty bulky. Even the "box" is big but it's also a very long connector physically, and the tab that protrudes even farther. The other thing that may not be immediately apparent is that it's not rated for all that many plug/unplug cycles. My QSFP cables have a "10 cycles" tag on them. Obviously they don't instantly die after 10 cycles, but still it's not something you are going to plug and plug every day for years. I don't remember if my SFP cables have one but I don't think it's significantly different. The SFP series are not a "consumer" connector, they are for servers that get racked once in a datacenter and then sit for 5 years, maybe have the cables re-organized once or twice.
It might well be something that you could fix with a "micro SFP" connector though. Slightly smaller box, much shorter, try to aim for higher cycle life. I think you would still retain a lot of the electrical benefits of SFP.
It's not very relevant for laptops, but SFP adapters also have an order of magnitude lower latency than base-T adapters. For things like your fileserver, it's preferable to use SFP if possible, that's why I mentioned I liked the Netgear MS510TXM above, 2 SFP links gives you one for your fileserver and one for a fiber link (to another switch perhaps), or you could do two SFP links and bond. There's some nice flexibility there.