iPhone 15 Pro Max can degrade Thunderbolt peripherals (2023) | Hacker News Reader

iPhone 15 Pro Max can degrade Thunderbolt peripherals (2023)

macperformanceguide.com

20 pointsMichaelZuo10 comments

This reminds me of two things I experienced when I added a Mac Mini (M2 Pro) to my setup.

1. When I connected my iPad Pro M1 to the Mac via a 10Gbps rated USB-C/C cable, it only connected at USB 2.0 speeds (480Mbps). However, when I used a USB-C to USB-A adapter, then a USB-A to USB-C cable to my iPad, it connected at 10Gbps. My suspicion is that when it has the full USB-C wiring on both ends, it might try to establish a Thunderbolt 4 connection, fail, and just fall back to USB 2.0, rather than trying USB 3.x?

2. On a slightly unrelated note: I found the USB-A ports (or rather, their controller) to be really unstable when using a hub, everything works fine when connecting devices directly to the Mac, but with any of the hubs I tried, I saw USB devices becoming unresponsive or resetting over time. A similar setup worked fine on my Windows PC. The most unstable was a simple (i.e. 3 USB-A ports and Ethernet) USB-C hub which I tested with an adapter ("proper" one with VL160 chip); for fun I also tested it with an ungodly chain of almost every USB-C/A adapter I had on the USB-C/TB ports, where it worked fine.

Having to do a bunch of troubleshooting to set up my USB peripherals on the Mac was a bit unexpected, at least the USB-C/TB ports seem to work well (other than that iPad weirdness), so I'm happy I went with the Pro model for the additional two ports.

(Note: While I didn't really approach this too methodically, I believe I tried enough combinations of cabling and hubs to exclude a simple issue like a faulty cable.)

For 2, I usually blame it on the hub; but it's hard to find, or even define what is a "proper hub". I genuinely don't know how they work (like, if I plug 4 external HDDs to a hub surely they have to split the bandwidth? Is there a limit?) and what spec they are supposed to follow to make they work 100 of 100 times across multiple OS.

I have ones only work well on PC, and ones only work well on MacOS in all these years. I tried to purchase not-so-cheap ones but at the end of the day it's still a gamble everytime.

Hubs are part of the USB spec I'm pretty sure. The hub's controller should also handle bandwidth bottlenecks.

As for the hubs in point 2, I am actually using a chain of three USB hubs between my Mac Mini and some of my peripherals (4 hubs if you count an internal one), which so far has worked without issues; I think all three of them caused instability on the USB-A ports. Again, the ports work fine when only one peripheral is connected directly, I plugged in two disk enclosures that saturate 5 Gbit/s and didn't see any issues when reading from both simultaneously.

Most of issues I encounter with hubs are during plugging/removing a device from it.

For example, I have at least 2 hubs that will lost all of their connected devices temporally if a new (externally powered) 3.5" HDD is connecting. They work fine after that. I assume it's related to their (poor) electric design than the information signal part.

Before stumbling on to this I always thought the bizarre Thunderbolt issues reported every so often were just due to cable/connector issues.

But apparently just connecting an iPhone to a Mac, and doing nothing with it, can somehow induce OTHER attached peripherals to degrade in their performance! Regardless of cable quality.

And somehow even the order of attachment can affect this.

So no wonder there are bizarre Thunderbolt issues…

This happened to me with a samsung t7 and my MBP. In the end it was a bad usb-c cable.

Same for me, but MacBook Air M1 and T7 Shield. But it doesn't always seem to be the cable. One of Samsung's was definitely broken and they replaced it, but it keeps happening with other cables too.

Was it a name-brand cable? Can you name names?

I was originally using the cable that came with the drive.

At some point I kept plugging it my Macs and sometimes it would go slow speed USB, and sometimes it would go to 10. I was plugging it into a CalDigit/OWC hub (depending on the Mac) and directly to the machine.

After realizing what was happening I just picked up a 20gbps (or 40, I can't remember) cable off of amazon and the problem went away.

I had a feeling it was doing this. Thanks for the insight!

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