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It’s crazy that the Ethernet chips consume more power (presumably - because of the heat) than the processor in the computer. How is driving 25Gb/s such a hot ta
by teaearlgraycold 2mo ago
It’s crazy that the Ethernet chips consume more power (presumably - because of the heat) than the processor in the computer. How is driving 25Gb/s such a hot task compared to driving multiple 40Gb/s Thunderbolt ports?
- wmf 2mo agoA Mac Studio is over 100 W while a 25G NIC is under 25 W (that's the power limit for a normal PCIe slot).
- ssl-3 2mo agoA normal x16 PCIe slot has always been able to supply up to 75w since the beginning.
- wmf 2mo agoA normal non-GPU PCIe x4/x8 slot that you'd use for a NIC provides 25 W.
- altairprime 2mo agoFor a 25G NIC, I’d be perfectly unsurprised if it demanded an x16 slot. I’d be more surprised if it didn’t have a power connector like a video card, though.
- StillBored 2mo agoI might be hallucinating, but IIRC this is now dependent on PCIe revision. More recent revisions have removed the slot power limits line, and so it works out that in theory a x4 slot (or any other size) can have a 75W load. IIRC this is stated in the middle of a giant section on up/down plugging. (but its also displayed in the pcie PowerLimit capabilities you can see with lspci)
- throwaway219450 2mo agoThey’re not that bad, but even a couple watts of power with no way to dissipate is going to get hot enough to burn you. Forced air cooling over a heatsink is really effective. 15W under load is much lower than a high end desktop CPU that can pull 150-200W. See also NVMe drives? They draw enough idle power to drain a laptop battery overnight, and will easily hit 60+C in a bad enclosure. That’s only a 10Gbps module. The USB4 enclosures are all heatsink.
- AnthonBerg 2mo agoAs I understand it, it takes a bit of anger to get electromagnetism to wiggle that fast over copper. Imperfect transistors using their full operational envelope to control a sort of chaotic thing? Fields and stuff.
- m463 2mo agocan confirm. anger causes loud fast communication that can be heard over background noise. I've heard anger using light-based signalling like sign language might be more efficient.
- teaearlgraycold 2mo agoThey get hot using fiber as well.
- NooneAtAll3 2mo agois thunderbolt not copper?
- AnthonBerg 2mo agoIt doesn't get as long! Long copper.
- kalleboo 2mo agoThunderbolt cables also have mini coax cables inside of them rather than twisted pair. https://www.youtube.com/watch?v=LBWnb0ZIlEA https://www.youtube.com/watch?v=LBWnb0ZIlEA
- frollogaston 2mo agoMaybe the NIC does a lot? In past experience, a whole Xeon CPU couldn't keep up with a 10gig NIC if it was sending/receiving min-size UDP packets. Even with Intel DPDK iirc.
- teaearlgraycold 2mo agoI believe the CPU gets an interrupt per packet. It’s just not designed to be interrupted that often.
- fragmede 2mo agoThat's what the DPDK Poll Mode is for.
- frollogaston 2mo agoRight, also ofc not an issue with sending
- colechristensen 2mo agoEthernet is isolated through transformers on the physical layer and they're always sinking power. Thunderbolt is just pushing current directly through. With ethernet it's for lots of reasons but a big one is not creating ground loops between distant equipment. If you didn't isolate the network cable would be sinking potentially amps of current between distant devices and that just isn't sustainable. You don't have this problem attaching USB between two devices.
- jauntywundrkind 2mo agoIt's distance. 25GbaseT is good for 30m+. Thunderbolt is good for 1m without active cables. Making the much more rugged signal is a much more intense job. And your computer already speaks the PCIe and thunderbolt. It has that probably on CPU. Here we have to receive USB, convert it to Ethernet. On much less up to date process nodes than your CPU. Third, until very recently for even 10Gbit it meant using a usb4<->pcie bridge chip which itself was hot, to provide a generic pcie connection, which then talked to a conventional network chip, so it was a double hop: USB <-> pcie <-> nic. I don't know if 25Gbit to USB direct convert is available yet but we've seen a wave of vastly cheaper 10Gbit adapters come out that are single chip USB<->nic, probably not pcie at all, that are much much cooler. 25Gbit is probably still not here yet, maybe?
- selectodude 2mo agoSomething like 5 percent of AI datacenter usage is just optics.
- Palomides 2mo agois 10W a lot of power? I absolutely don't believe the cpu is using less than that while pushing 25Gb out you can look up the rated power use of a connectx4 card, they do a lot of offloaded computation, too
- Aurornis 2mo ago> It’s crazy that the Ethernet chips consume more power (presumably - because of the heat) The NIC in this setup was released 12 years ago. It's built on a very old process.
- monster_truck 2mo agoThere are no shortcuts in networking. It's quite easy to spend a 2-3x+ premium on a switch or adapter capable of non blocking line rate on every port simultaneously only to then have it fall over to a fraction of that in the form of lots of tiny packets. This is why we have things like QoS, flow control, and ECMP