Long before everyone got used to plugging things into a familiar rectangular port (and flipping the cable around three times before getting it right), there was another connector quietly doing most of the heavy lifting. The serial port wasn’t pretty, it wasn’t fast, and it definitely wasn’t friendly, but for decades, it was the way you connected almost anything that wasn’t already inside your computer case.
It’s easy to forget just how much we owed to that chunky D-shaped connector on the back of every PC. In a lot of ways, it was the original universal connector. It paved the way for everything USB later did better, and even gave USB part of its name.
The serial port had a long and surprisingly important run
It quietly powered decades of computing before anyone knew what USB was
The serial port, most often based on the RS-232 standard, has roots going all the way back to the 1960s, when it was created to standardize communication between different vendors’ equipment. By the time the IBM PC arrived in the early 1980s, RS-232 add-on boards were already being made to handle just about any peripheral you could think of. If you owned a PC in the 80s or 90s, odds are you spent some quality time staring at the back of your tower trying to line up those tiny pins without bending them.
The fact that USB stands for Universal Serial Bus isn’t a coincidence, either. USB is itself a serial protocol, and it was built to take over the role serial ports had been holding down for years. Serial ports didn’t just come before USB; they were the blueprint USB iterated on.
Quiz
USB standards & connectors
Trivia Challenge
From clunky Type-A plugs to lightning-fast USB4 — test your knowledge of the universal serial bus revolution.
HistoryConnectorsSpeedsStandardsHardware
In what year was the original USB 1.0 specification officially released?
Correct! USB 1.0 was released in January 1996 by a consortium led by Intel, Compaq, Microsoft, and others. It aimed to replace the chaotic mix of serial ports, parallel ports, and PS/2 connectors that plagued early PCs.
Not quite — USB 1.0 launched in January 1996. It was developed by a consortium including Intel and Microsoft to simplify the frustrating tangle of legacy ports on personal computers at the time.
What is the maximum data transfer rate of USB 2.0, also known as ‘Hi-Speed’ USB?
Correct! USB 2.0 tops out at 480 Mbps, which is why it earned the ‘Hi-Speed’ label when it launched in 2000. That was a massive leap over USB 1.1’s 12 Mbps Full Speed ceiling, making it practical for external hard drives and cameras.
Not quite — the correct answer is 480 Mbps. USB 2.0 is branded ‘Hi-Speed’ and launched in 2000, offering a 40x improvement over USB 1.1’s Full Speed 12 Mbps mode, which made external storage far more viable.
Which USB connector type was specifically designed for use with mobile phones and cameras, featuring a distinctive 5-pin trapezoidal shape?
Correct! USB Mini-B was the go-to connector for early digital cameras and mobile phones before being largely replaced. It features a recognizable five-pin trapezoidal design and was formally specified in USB 2.0, though it has since been superseded by Micro-B and USB-C.
The correct answer is USB Mini-B. It was the standard connector for early digital cameras and many mobile phones, featuring a 5-pin trapezoidal shape. It was eventually displaced by the slimmer Micro-B connector, which allowed for thinner device designs.
USB 3.0 was later rebranded by the USB Implementers Forum. What is its current official name?
Correct! The USB-IF rebranded USB 3.0 as USB 3.2 Gen 1 to fit into a unified naming scheme. It still delivers the same 5 Gbps ‘SuperSpeed’ transfer rate — the confusing renaming was meant to streamline the standard’s versioning but arguably made it more complicated.
Not quite — USB 3.0 is now officially called USB 3.2 Gen 1. The USB Implementers Forum rebranded the entire USB 3.x family to create a unified naming structure, though the 5 Gbps SuperSpeed performance of the original USB 3.0 remains unchanged.
What key physical feature makes USB Type-C different from all previous USB connector types?
Correct! USB Type-C’s most celebrated feature is its symmetrical, reversible design — you can plug it in either way without fumbling. Introduced in 2014, it also supports far higher power delivery and data speeds than older connectors, making it a true universal solution.
The standout feature is its fully reversible design — you can insert a USB-C plug either way up, ending the frustration of guessing the correct orientation. Introduced in 2014, USB-C also supports higher power delivery and data speeds than its predecessors.
Which organization is responsible for developing and publishing the USB specification?
Correct! The USB Implementers Forum (USB-IF) is the non-profit organization formed by the original USB developers to maintain and promote the USB specification. Founded in 1995, it certifies compliant products and grants the right to use the official USB logo.
The correct answer is the USB-IF, or USB Implementers Forum. This non-profit was founded in 1995 by the companies that originally developed USB, including Intel and Microsoft. It maintains the specification, runs compliance programs, and certifies products to carry the USB logo.
What maximum power output did USB Power Delivery 3.1 introduce, enabling charging of high-performance laptops?
Correct! USB Power Delivery 3.1, released in 2021, dramatically raised the ceiling to 240 watts using Extended Power Range (EPR) mode. This is enough to charge even power-hungry gaming laptops and workstations over a single USB-C cable, replacing bulky proprietary chargers.
The answer is 240 watts. USB Power Delivery 3.1, introduced in 2021, added an Extended Power Range (EPR) mode that maxes out at 240W over a USB-C cable. Earlier PD versions were capped at 100W, which was insufficient for many high-performance laptops.
USB4, released in 2019, is based on which company’s proprietary technology that was donated to the USB-IF?
Correct! Intel donated the Thunderbolt 3 specification to the USB-IF, which became the foundation for USB4. This means USB4 at its fastest tier (40 Gbps) is technically compatible with Thunderbolt 3 devices, blurring the line between the two standards significantly.
The correct answer is Intel’s Thunderbolt 3. Intel donated its Thunderbolt 3 spec to the USB Implementers Forum, and it became the basis for USB4. The top USB4 speed tier of 40 Gbps mirrors Thunderbolt 3, and the two standards share a high degree of compatibility.
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Here’s how the serial port actually worked
One bit at a time, and not much fuss about it
A serial port does exactly what its name suggests. It transfers data one bit at a time, in sequence, over a single line, instead of sending multiple bits side by side like a parallel port would. That sounds slow, and honestly, it kind of was, but it also made the wiring much simpler and the cables much cheaper.
Communication was asynchronous and point-to-point, meaning one device talking directly to one other device, with no central traffic cop sorting things out. That simplicity is actually part of why serial connections are still used today in industrial environments, networking gear consoles, and embedded development, where reliability matters more than raw speed.
The similarities to USB are bigger than you might think
USB didn’t reinvent the wheel, it just made it round
When you put serial and USB side by side, the family resemblance is obvious. Both are serial protocols, both are designed to be a general-purpose way to connect peripherals to a computer, and both were built around the idea of standardization across manufacturers.
The serial port was effectively the first attempt at a “plug anything into this” interface on the PC. Mice, modems, printers, scanners, barcode readers, label printers, GPS units, and an endless list of industrial equipment all spoke serial at one point or another. That same mindset, where one port could handle just about any kind of accessory, is exactly what USB was designed to deliver, just with a lot fewer headaches.
There’s even a direct lineage in hardware. Plenty of modern devices that present themselves as USB are actually just serial devices wrapped in a USB shell, thanks to chips like the FTDI family that emulate RS-232 over USB. Open up Device Manager, and you’ll still see them show up as COM ports, decades after the original ports vanished from most computers (but not all).
Where the serial port fell short
It was great for its time, but its time had limits
For all its strengths, the serial port had some real shortcomings, and they got harder to ignore as computing got more demanding. The biggest one was speed. RS-232 typically topped out somewhere between 20 Kbps and 115.2 Kbps in real-world use, with a theoretical ceiling around 1 Mbps under ideal conditions. That was fine for a mouse or a modem. It was hopeless for a scanner, a webcam, or an external hard drive.
There was also the matter of how few ports you actually got. A typical PC had one or two serial ports, and each one could only talk to a single device. If you wanted to use a modem, a serial mouse, and a label printer, you were either swapping cables constantly or buying expansion cards.
Setup wasn’t exactly user-friendly, either. You had to manually match settings like baud rate, parity bits, and stop bits on both ends, and there was no way for the computer to identify what was actually plugged in. Serial ports also couldn’t deliver any meaningful power, the connectors were big and held in place with screws, and the signal was vulnerable to noise over longer runs.
Why USB was such a leap forward
It took everything serial did and turned the dial up
USB didn’t just edge out serial, it lapped it. The most obvious win was speed. Even the original USB 1.1 ran circles around RS-232, and modern USB versions transfer data orders of magnitude faster than anything serial ever could.
It was also genuinely universal in a way serial never quite managed (well, aside from the whole USB color code thing). A single USB host can fan out to dozens of devices through hubs, and each device can identify itself to the computer automatically, negotiate its speed, and load the right driver without you ever knowing what a baud rate is. That’s a massive quality-of-life upgrade compared to the manual configuration dance that serial demanded.
USB also brought power delivery to the party. Suddenly, you could run a whole peripheral off the same cable that carried its data, which is something serial was never really built to do at scale. Add in hot-swapping, smaller and more durable connectors, and compatibility with mass storage devices, and it’s pretty clear why USB pushed serial off the back of the average PC by the 2010s.
Gone from most PCs, but never really gone
The serial port, along with plenty of other old ports, has faded from consumer machines, but calling it obsolete still feels a little unfair. It’s quietly alive and well in industrial automation, networking closets, scientific labs, and the embedded world, where its simplicity, reliability, and long-distance capability are still genuine strengths.
More importantly, it laid the groundwork for everything we now take for granted with USB. The idea of one standardized port that can talk to almost any peripheral didn’t start with USB, it started with that big D-shaped connector on the back of an old beige tower. USB just took the concept, fixed the rough edges, and ran with it.
