What are your thoughts on this? (besides "You have too much time!" or "First-world problems!" :D)Įdit: thanks to /u/gmcinalli I've tested everything again for the Realtek chip but using the original Realtek driver this time. ![]() I'm also sure that on a weaker or older machine (like a MacBook Air) this additional CPU load could bottleneck network throughput. Some USB-C adapter are also quite unstable which results in connection or packet loss. Power users transferring a lot of data over the network, for example to and from a NAS, and also run computational demanding tasks may want to avoid USB-C Ethernet adapters. For typical web browsing the additional overhead is negligible. What does this mean to the average user? Probably nothing. They're internally connected via PCIe and will perform similar to or even better than the BCM5701. Most (real) Thunderbolt 3 docks use an Intel, Broadcom or Aquatic chip if they have an Ethernet port. Wifi has slightly higher CPU impact than Apple's Ethernet adapter but way less than the Realtek Ethernet. I also couldn't compare it to WiFi as I don't have a WiFi router that is capable to transfer 1Gbps consistently. I haven't tested it with other operating systems (Windows/Linux) yet. The fact that AppleUserECM (as you may guess from its name) is running in user-space and not in kernel-space as the Broadcom driver. USB overhead? The Broadcom chip uses PCIe over Thunderbolt. This would mean that the CPU now has to do all the computations instead. There are know issues with a lot of USB chips when offloading is enabled so Apple might just went the safe route. I don't have a definitive explanation for this but these are my (educated) guesses:Īpple's driver for the Realtek Chip (AppleUserECM) has all offloading capabilities disabled. ![]() Some results seem odd (like the FTP ones) but I tested it multiple times and this is the result.Īs you can easily see, the Realtek Chip causes way higher CPU load across the board. I made sure, that network was always saturated by the test and used a dedicated switch with just this machine and the Synology NAS connected.ĬPU usage is in unix format (100% = 1 CPU core) Tests were done 3 times and data was averaged. ![]() Only CPU usage caused by kernel_task and AppleUserECM (Apple's USB Ethernet driver) was measured Test file for SMB and FTP was 4GiB of random data (pre-generated). WiFi Router: AVM FritzBox 6591 Cable (5Ghz 802.11 AC, 1300Mbit/s)Ĭlean install, all apps closed besides the ones relevant for this test.ĬPU usage measured with top in terminal in 1 second delays. Test Target: Synology DS416 connected with 2 links (LACP). Machine: MacBook Pro 16": i9 2,4GHz 32GB RAM Catalina 10.15.5 Results are updated and apparently it's Apple's driver causing this issue. I compared this data to the other hubs I own for verification and results are comparable.Įdit: The test was re-done with the original Realtek driver for macOS. I used a plain Dell USB-C Gigabit Ethernet adapter as Realtek representative to make sure no other Hub "features" interfere with the test. I compared it to the Apple Thunderbolt 2 GbE Adapter (Broadcom BCM5701) together with the Apple Thunderbolt 3 to Thunderbolt 2 adapter to connect it to my 16" MBP. ![]() When copying data to or from a NAS or otherwise pushing high amount of traffic through it, CPU load goes up pretty high (for just transferring data with about 115MB/s). Well, besides that this chip is as low-end as you can go, it also causes high CPU usage on macOS (haven't tested on other OS yet). I just did some testing and found out that (probably) all USB-C hubs on the market that come with an Ethernet port use the Realtek RTL8153 network chip.
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