Well with Apple making a huge statement by moving to a single connector for everything, it's time to look back and figure out how we got here. So here in chronological order is a short incomplete history of computer cabling and some explanation for how we got here.
The future is that all peripherals, monitors, external disks, network connectors will fit into a single physical connector called USB/C. It is the highway on which everything will eventually travel. In the mean time you dongle your way to the future with existing hardware. One confusion is that USB is actually a family of connector standards USB/A, USB/B, mini-USB, micro-USB and USB/C and a family of protocols that can run on top USB 1, 1.1, 2, 3, 3.1. So you can have a USB/A connector that supports USB 3.1 and a USB/C connector that support USB 3.1, Thunderbolt 3 and DisplayPort 1.3. Confused yet.
On that one hardware highway, there will be different protocols. Not unlike the way the Internet works, there is one connection, but web pages, video, email, etc. all use different exchange protocols. Sort of the way one road can have many different kinds of cars and trucks tuned for different uses. Those protocols are going to vary quite a lot based on low cost (USB 2, 3 and 3.1) and performance for specific purposes (Thunderbolt 3 for external disks and graphics cards vs. Displayport 1.2 and soon 1.3 for monitors).
The big shoe to drop will be DisplayPort 1.3 which will allow 5K and 8K video output and wide dynamic range on the same USB/C connector.
So for example even with USB/C you need a collection of cables:
- USB/C to USB/A supports USB 3 by Nona ($11) or AUKEY ($3.50 each). Maybe the simplest example, this converts a USB/C to USB/A connector for use with USB/A cables. It is limited to 5Gbps of USB 3.0 though but costs just $11.
- USB/C to USB/C supports Thunderbolt 2 (20GBps) Cable Matters. This cable supports 20GBps using Thunderbolt. It costs $22 so much more than USB 3 support.
- USB/C to USB/C support Thunderbolt 3 (40Gbps) Startech and Cable Matters. The same cost as the Thunderbolt 2 cable so be careful!
- USB/C to Displayport supports Displayport 1.2 Cable Matters. For $20 get a cable that is DisplayPort for video connection up to 4K at 60 hertz. In contrast the Apple version of this only works to 30 Hertz because it is DisplayPort 1.1 and it costs $49!
The IBM PC (c. 1980)
In a brief history of time, the original IBM PC had a different hardware connector and a specific protocol for every peripheral. Computers were slow enough back then and as today, cost vs performance was a big driving factor. The slower peripherals used cheaper connectors. Also back then size wasn't as much of an issue and electronics dominated costs, so having a bunch of connectors wasn't a big deal. So in the back of the original IBM PC you would see:
- Keyboard and Mice. These were the slowest peripherals and used a serial connection running as slow as on a physical connector called DB-9 (9 pins right?). IBM migrated the same nine pins to with the IBM PS/2 to a cleverly named PS/2 connector which was the cool round thing.
- Joystick. This was an analog input for joysticks
- Video. Back then video was analog, you basically fed the monitor with the actual RGB values on a CGA, EGA then VGA connector which was 15 pins and easy to break by the way 🙂 Even today many monitors still have this as the fall back connector.
- Printers. In the day, when you connected a printer or even a terminal to a computer you typically had either a parallel connector called a Centronix interface or a serial connection with a big DB-25 connector using RS-232 serial connection.
- Modems. These were also serial devices using RS-232 and usually a DB-9 connector connecting to the phone systems with RJ-11 jacks.
- Floppy disk. These also had a dedicated connector
- Networking. The ethernet was a huge coax cable so that's what you got on the few machines with any kind of networking.
- Internal disks. OK not really part of the cable story, but part of the larger unification is that disks also had their own protocol and connectors called ATA and then IDE. The big disks used something more expensive called SCSI.
- Internal cards. These used the IBM bus standard and were completely different from the outside world. They were high speed parallel connectors either 8-bit or 16-bit.
- Power. All of these peripherals were separately powered with their own connectors.
The main point of this was that we started with a very diverse collection of hardware and protocols tuned for very different uses. Everything up until that point was a different wire for each kind of peripheral
USB Convergence (1990s)
The first big change for cabling came with the universal serial bus. Technology moved forward and now instead of a dedicated controller board for each peripheral, a single chip could handle it and as costs plummeted, peripherals started to merge at the low end. At the high end, the drive was still on performance so the cables changed as physical connectors did.
However as USB moved forward the connectors changed significantly from USB A to B to mini USB to micro USB. So you ended up with a huge number of different cables all supporting some version of the USB protocol although the faster peripherals continued to used dedicated physical connectors and protocols. The big change was the move to serial protocols because at higher data rates, the skew on parallel connectors was a problem and electronics got cheap enough that they could handle the additional processing needed for serial connections
- Keyboard, Mice, Joystick, Printers, Modems, Floppy Disks. USB 1.1 was the version that really took off providing 1.5Mbps and 12Mbps high speed in 1996. This led to so called legacy-free PCs with much simplified systems. This was a huge simplification of the back of a PC although the connectors were a mess. There was USB/A on the back of most PCs, the the peripherals themselves had a wide range of connectors from USB-B, mini-USB, 4-pin USB and finally micro-USB. This was the first connector that began supplying power as well at 500mA up to 1Amp
- Firewire/400 and 800 External drive or eSATA. Apple of course had their own course of things and they used Firewire instead for things like external disks. eSATA (external SATA) was the equivalent PC standard, but these too were niche products
- DVI and HDMI Video. At this point, video also moved into the digital world as controllers in CRTs and then flat panels could process digital. Still the computer world (DVI) and the home electronics world (HDMI) were still not quite converged and both used big thick cables cables that were quite different.
- SATA internal drives. The disk drives also moved to a serial model with eSATA as variant for connecting external drives.
- PCI bus. The internal bus of PCs because PCI, more on the this later, but the emergence of PCI was the start of convergence between the internal and external worlds.
- Ethernet. The world moved to twisted pair ethernet and RJ-45 connectors for 100Mbps fast ethernet.
- Power. Nearly all the "real devices" used a wall wart of a high power source.
USB/A and USB 3 Rules them all (2000s)
As the beat went on, USB went from being a slow bus for peripherals to big Intel support and very high speed. The new USB 2.0 was 480Mbps and then USB 3 at 5Gbps and effectively killed all but the fastest devices including external disks for the first time with speeds of 20MBps possible, so this PC would have:
- Peripherals and external hard drives. USB/A connector to any of a large number of USB physical connectors. Most of these could be self powered at 10 Watts to 20 Watts. (1-2Amps at 5V).
- USB Keys and hard drives.. These were a new form of peripheral as SSDs got cheap enough and USB 3 was fast enough to support them
- Dual DVI and HDMI with most displays working fine at 1080p 120 hertz with DVI, but not with HDMI.
- PCI Express. This was Intels big move to a fast serial bus internally
- SATA internal drives ruled although SAS following SCSI was for enterprise systems.'
- Ethernet. RJ-45 continues to rule as speed move to 1GBps
Internal and external merge (2010s)
In our current decade as processing got faster, the core PCI Express protocol would now work outside. This was a huge change in technology as having a single protocol across internal and external was a great simplification. At the same time, as bus speeds went for USB 3.1 4oGbps even the highest demand peripherals like video and disk could use a single connector. As a result the latest MacBook Pro could get away with a single external connector and a single internal protocol (PCI Express).
The biggest confusion is that cables can look alike (they both have USB/C connectors), but they are spec'ed to carry different protocols. So you will have cheap USB/C cables that only support USB 3.1,
- All external peripherals. USB/C connector to USB 3.1 at 10Gbps. This protocol is tuned for loosely coupled devices so there are some specialized protocols for specific purposes (disk and video).
- Self powered even for laptops. USB/C power. Another big change is that power can also be supplied up to 100 watts so that most laptops could be powered from a USB/C
- External disk and graphics to Thunderbolt 3 on USB/C. For the first time high speed internal components like disk and even the graphics card can move outboard. The Thunderbolt 1, 2 and 3 provides 10, 20 and 40Gbps that are really PCI Express 1x, 2x and 4x exposed externally. A conventional hard disk has a speed of 600MBps (basically Thunderbolt 1) while the fastest SSD barely saturates a Thunderbolt 3 connection. Thunderbolt unlike USB 3.1 is designed for these fast peripherals, so be careful that you are buying a USB/c Thunderbolt 3 cable when you connect them.
- Monitors use DisplayPort Alt Mode with DisplayPort 1.2 on USB/C. While there remain some transitional monitors using a mini-Displayport or Displayport connector, these were only used for a short time. The new USB/C connector can carry digital video to monitors efficiently. Monitors in this timeframe had a huge number of transitional connectors. Intel started the DisplayPort family with DisplayPort and mini-DisplayPort connectors and with protocols called DisplayPort 1.1, 1.2 and 1.3 (each with higher power) before they decided to abandon the connectors and move everything to USB/C connectors. Make sure you get a USB/C cable with DisplayPort 1.2 support which is part of the Thunderbolt 3 spec. Confused yet? The monitor world has had a huge transition because 4K UHD really blows out the bandwidth requirements. To get to 4K at over 60 hertz plus wide dynamic range requires moving to DisplayPort 1.3 which isn't yet int he spec.
- Disks use PCI Express and m.2. While SATA lives on as a legacy connection, the world moved to SSDs and they use a PCI Express protocol with a new connector called m.2. The m.2 is just a smaller version of the PCI Express slot and comes in 1x, 2x and 4x versions.
- Graphics cards use PCI Express. Like the the previous world, graphics cards need 16x lanes and PCI Express is the only way to provide them. External graphics cards only have 4x lanes on Thunderbolt 3 so it will be interesting to see how they do.
- Ethernet using USB/C to RJ-45 convertor cable.