Rambling Rows

Every USB-C port looks the same too. Some are quietly slower

Sat, 30 May 2026 10:06:08 +1000

Last time it was the cables lying to you. You binned the mystery leads, bought the certified ones with the speed and watts printed on the side, labelled the survivors. Good. You fixed the drawer.

Now look at the laptop itself, because it is about to play the same trick on you. Two ports, same oval socket, same confident silver moulding. One is fast. One is not. And nothing on the outside tells you which is which.

The connector is a shape, not a promise. That was true of the cable. It is just as true of the hole you plug it into.

The MacBook Neo has a slow port and a fast port

Apple’s own support page is unusually blunt about this. The MacBook Neo has two USB-C ports, and they are not equals. Face the left-hand side of the machine: the port furthest to the left is your fast one, USB 3, and it is the one that drives an external display. The port furthest to the right is USB 2 only. Either will charge the laptop, but only one will move data at speed.

Sit with the gap that hides behind those two names. USB 2 tops out at 480 Mbps. USB 3 on this class of machine runs at 5 Gbps, and a real SATA SSD on it will push something like 430 to 520 MB/s. That is roughly ten times the throughput, from the same socket, on the same laptop, decided entirely by which side you reached for.

So you plug your backup drive into the nearest port, the drive mounts, the copy starts, and it crawls. Nothing warns you. macOS does not pop up a dialog saying “you have chosen the slow hole.” It just quietly underperforms, exactly the way the wrong cable did, and you blame the drive.

The fix is free. Use the left port for anything you care about - displays, SSDs, card readers - and leave the right one for the mouse, the keyboard and charging.

On other Macs, look for the lightning bolt

Most Macs are not split this way. The bigger machines run Thunderbolt on every USB-C port, which is the good news. The catch is working out which tier you have, because the tiers are a ladder and the rungs are far apart.

The tell is printed right there on the chassis. A lightning bolt symbol next to the port means Thunderbolt - Intel-certified, video-capable, the high-speed lane. Apple even stamps it above the ports on machines like the 2021 iMac so you know which ones to use for a display. No bolt and you are likely looking at plain USB-C, which on the MacBook and some Mac mini configurations is a real step down.

Where you land on the ladder depends on the year and the chip:

Thunderbolt 3 and 4 both run 40 Gbps. A good external SSD on one of these will sustain somewhere around 2,400 to 2,800 MB/s in the real world. That is the floor for any Apple Silicon MacBook Pro, the M-series Air and most of the desktop line.

Thunderbolt 5 lifts the ceiling to 80 Gbps, and it is on the 2024-and-later 14 and 16-inch MacBook Pro with Pro or Max chips, the 2025 Mac Studio and the M4 Pro Mac mini. Unless you are running multiple 8K streams or an external GPU enclosure, you will struggle to feel the difference over Thunderbolt 4 today. It is headroom you are buying, not everyday speed.

The point is not to memorise the matrix. It is to glance at the port before you commit a big transfer to it. The bolt is the same kind of signal as the speed-and-watts logo on a certified cable. It is the manufacturer telling you, in the one place it cannot easily lie, what this lane can actually do.

The migration trap, and why it can cost you a whole afternoon

Here is where the cable and the port conspire, and where SmartFriend™ Peter Marks earns his trademark again. When you move to a new Mac, Migration Assistant will happily transfer everything across. The question is how, and the difference between the right answer and the wrong one is measured in hours.

Get it wrong and a big migration over Wi-Fi can run two to three hours for 100 GB, and considerably worse if your wireless is busy or the libraries are large. People routinely report sittings that stretch past seven hours. Get it right - a Thunderbolt cable between the two machines, plugged into a Thunderbolt port at both ends - and the same job drops under an hour. One real-world account moved 350 GB in less than 45 minutes that way.

Two things have to line up, and this is the whole lesson. You need the right cable, a genuine Thunderbolt or high-speed USB-C lead rather than the charge-only one that came with something else. And you need the right port at both ends, the one with the bolt, not the USB 2 afterthought. Miss either and you are back on the slow lane, or worse, back on Wi-Fi.

That last bit is the sting. On Apple Silicon, Migration Assistant does not always grab the cable even when one is plugged in. It will sometimes default to Wi-Fi and never tell you it made that choice. So before you walk away, look at the transfer window and check the connection indicator actually says Thunderbolt. If it says anything else, you are about to lose an afternoon to a cable that was sitting there ready the whole time.

The same rule, all the way down

It is the same discipline from the cable post, pushed one layer deeper. The socket will not tell you the truth, the cable might be lying, and now it turns out the port has opinions of its own. The only honest signals are the ones printed where they cannot easily be faked: the speed-and-watts logo on the lead, the lightning bolt on the chassis, the connection indicator in the transfer window.

Read those three and you will never again hand a ten-times-faster job to the slow port out of laziness. Ignore them and the machine will let you, quietly, every single time.

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Every USB-C cable looks the same. They are lying to you

Sat, 30 May 2026 08:22:08 +1000

Open the drawer where you keep your cables. Go on. Somewhere in that tangle are two USB-C cables that look identical, came in similar boxes and feel the same in your hand. One will charge your laptop at full speed and drive a 4K monitor. The other can barely run a mouse.

The connector tells you nothing. That is the whole problem.

USB-C is a shape, not a capability. A cable wearing that oval plug might be a USB 2.0 charging lead doing 480 Mbps and 60W, or it might be a Thunderbolt 4 cable pushing 40 Gbps and 240W. Same socket, wildly different cable. And the day you discover the difference is usually the day your “fast” transfer crawls or your dock refuses to wake the second screen.

I went looking for a way to tell them apart. That hunt is what this post is about.

The names are a deliberate mess

Start with the standards, because the branding is hostile by design.

USB4 is the current baseline worth caring about: 40 Gbps data, up to 100W charging, and it carries video. The newer USB4 version 2.0 doubles that to 80 Gbps. Thunderbolt 4 is Intel’s tighter version of roughly the same thing - guaranteed 40 Gbps, mandatory PCIe tunnelling and enough certified headroom to run dual 4K displays. Thunderbolt 5 lifts the ceiling again to 80 Gbps, 120 Gbps in bursts, and 240W.

The trap is everything below that. “USB 3.2 Gen 2x2” sounds fast and means 20 Gbps. “USB 3.2 Gen 1” is the old 5 Gbps spec wearing a newer name. A cable can legally say “USB-C” and do almost nothing. None of this is printed where you can see it when the cable is plugged in.

What you can actually see

Pick the cable up and look at the moulding near the connector. Certified cables now carry a USB-IF logo that pairs a speed with a power figure - you want to see something like 40Gbps / 240W stamped on it. Under the current rules a cable cannot just claim a speed, it has to declare its wattage too. That combined logo is the single most reliable thing you can read with your eyes.

A lightning bolt with a number next to it (3/4/5) means Thunderbolt, Intel-certified, higher tier. Worth more than the USB logo because the testing is stricter. Choose Thunderbolt 4 in most cases. Few but video pros with top gear will need Thunderbolt 5.

Now the bad news. Plenty of perfectly capable USB4 cables ship with no marking at all. Absence of a logo proves nothing, and a printed claim is only as honest as the factory. Counterfeit cables print whatever they like. So the visible check narrows the field, it does not settle it.

One physical tell that does hold up: length. A passive 40 Gbps cable can only manage that speed up to about 0.8 metres. If a cheap two-metre cable swears it does 40 Gbps passively, be sceptical.

Ask the cable itself

This is where it gets clever. Better USB-C cables contain an e-marker - a tiny chip in the connector that tells your computer, over the CC pins, exactly what the cable can carry: current rating, data speed, vendor, Thunderbolt support. The cable introduces itself. You just need something to listen.

The app that prompted this whole post is WhatCable, and it is worth a clarification up front: it is a Mac app, not Windows. It lives in the macOS menu bar, reads the e-marker and Power Delivery data your Mac already has, and translates it into plain English - which cable, what speed, and crucially whether the cable, the charger or the Mac is the thing throttling you. There is a catch: it needs Apple Silicon. Intel Macs do not expose the data.

You do not strictly need the app, either. macOS already exposes most of this. Hold Option, click the Apple logo top-left, choose System Information and open the USB section. Each device shows its negotiated link speed and the power it has been allocated. (Hat tip to SmartFriend™ Peter Marks for the reminder.)

Here is what that looks like in practice, and it is the whole argument in two screenshots. I plugged the same Samsung T7 Shield SSD - same serial number, same drive - into my MacBook Pro through two different cables. On the good cable it sat on the USB 3.1 bus at 10 Gb/s, drawing 4.48W. On the second cable the identical drive landed on the USB 2.0 bus at 480 Mb/s and just 2.5W. Same socket, same SSD, twenty times slower and starved of power, purely because of the lead. Nothing warned me. The drive just mounted and quietly crawled.

On Windows the closest equivalent is USB Device Tree Viewer, a free utility that lays out every connected device with its negotiated speed and power, so you can see which cable is quietly capping a transfer. It reads what Windows exposes rather than interrogating the e-marker directly, but for “why is this slow” it does the job.

If you want the ground truth, a hardware tester like the POWER-Z KM003C reads the e-marker chip straight off the cable, no operating system in the way. That is the device the cable nerds actually trust but it’s over A$100.

Why bother

Because the wrong cable taxes you twice. Charge speed drops to whatever the weakest link allows, so your laptop sips when it should gulp. And data transfers fall back to the slowest mode both ends can agree on, which on a mislabelled cable can be 480 Mbps when you were promised 40 Gbps. Nothing breaks. It just quietly underperforms, and you blame the laptop.

So here is the move. Bin the mystery cables. Buy USB-IF certified ones with the speed-and-watts logo printed on them or Lightning icon and 4, and label the survivors. Then install something that can read the e-marker, because the connector will never tell you the truth and the print on the side might be lying.

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