Cable, connector, and adapter confusion

One of the most common questions I’ve received over the years comes in two forms:

  • I am trying to connect [something to something else] and don’t know what cables I need.
  • I am buying a new [iPhone, iPad, Mac] and need to connect it to [my old printer, my old external drive, an arc welding machine] and don’t know how.

I want to recommend two resources, one (almost) free and one that costs money. First, the (almost) free one: MacTracker. MacTracker is a database of Apple devices (desktop and laptop and server Macs, cameras, displays, iPhones, iPads, Newtons, printers, watches, major pieces of software, etc.) with dates of when they were introduced and discontinued, what software they came with and what software they are compatible with, what ports they have, etc.

You want to know what kind of ports you can find on a Macintosh Performa 600? MacTracker will tell you it has a DB-15 display port and a DB-25 SCSI port, which means it can’t be connected to any modern equipment; even the keyboard and mouse use ADB connectors incompatible with anything used today.

A MacBook Pro from 2008, on the other hand, does come with USB ports, but they are USB 2.0 ports, far slower than the USB-3 or Thunderbolt 4 ports used on a MacBook Pro from 2021. The 2015 MacBook also has a VGA port for external video, incompatible with the 2021 model using HDMI for external video.

You can get MacTracker for your Mac from either the Mac Tracker website,

or from Apple’s Mac App Store,

You can also get it for iOS (both the Mac and iOS versions contain the same information) from the iOS App Store,

I say it is “almost free” because the developer, who has been working on MacTracker for decades,

has devoted vast amounts of time and energy to this endeavor. Say nice things to him; he’s Canadian.

Knowing what ports your Mac or iPhone or Newton has is only half the battle. The next challenge: cables and adapters. It is possible to plug (some) iPads into an external disk drive, but getting the right cables and adapters can be a challenge. An example: I recently could not understand why my Thunderbolt RAID would not work with my new M1-powered Mac mini. I ran a cable between the two, and it fit perfectly, but nothing happened.

The problem? I was using a USB-C cable, which looks almost identical to a Thunderbolt 4 cable. But while the connectors look the same, the USB-C cable lacks the chips inside the connectors that make them Thunderbolt 4 cables. Thunderbolt 4 cables are backward compatible with USB-C, but you can’t use a USB-C cable to connect two Thunderbolt 4 devices. There are also critical speed differences:

  • Thunderbolt 4 to USB 2.0 device (with adapter): maximum of 480 Mbps (in theory, 48 megabytes per second)
  • Thunderbolt 4 to USB 3.1 device (with adapter): maximum of 10 gigabytes per second
  • Thunderbolt 4 to USB 3.2 device (with adapter): maximum speed of 20 gigabytes per second
  • Thunderbolt 4 to Thunderbolt 4 device: maximum speed of 40 gigabytes per second

Once I grabbed the right cable, my Mac mini was very happy with the RAID, and the RAID was impressively fast. Fortunately, I both knew what the problem was, and I had the right cable.

If you lack such experience, I highly recommend you get a brand-new book, Take Control of Untangling Connections. While I haven’t purchased the book, the publisher has a free preview of the book,

and it looks like the perfect reference for those who haven’t spent half a century plugging computer equipment into things. The book is $9.99, and you can purchase and download a copy (in PDF, Kindle, or iBooks format) in one step:

 Not only does it tell you which cables do what, it also offers advice on how to reduce cable clutter. My personal record: I had a Mac IIfx once upon a time that had 11 devices plugged into it. One computer, 11 devices. The computer and peripherals spilled off the desk and onto two adjacent tables. Just periodic dusting was a major technical exercise.

Knowing what cables can be used to connect devices is critically important if you want to add a scanner or printer or external disk drive or you are trying to migrate older devices to a new machine. Invest in some reference material; it can save you tremendous amounts of time, and money.

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