The problem: struggling with ports and IRQs
In the early 1990s, connecting peripherals to PCs was a mess. To set up any PC, you had to use a handful of different types of incompatible ports and connectors. Typically these were a keyboard port, a 9- or 25-pin RS-232 serial port and a 25-pin parallel port. In addition, PC game controllers used their own 15-pin standard, and mice were often connected to serial ports or proprietary cards.
At the same time, peripheral manufacturers began to run into data rate limits in existing ports used for peripherals on PCs. The demand for telephony, video and audio applications grew. Traditionally, vendors had circumvented these limitations by introducing their own proprietary ports that could be installed as add-in cards, but that increased costs and increased compatibility issues between machines.
And finally, adding a new peripheral to a PC was a headache. It often meant configuring technical details such as IRQ settings, DMA channels and I / O addresses so that they did not conflict with other devices installed on the system. (Average computer users don’t have to think about this anymore.) There had to be an easier way.
The solution: USB
Relief would soon come in the form of a single port that could unify the industry – the Universal Serial Bus. USB originated as a joint project in 1994 between eight high profile companies: Intel, Microsoft, IBM, Compaq, Digital Equipment Corporation, NEC and Northern Telecom. After development for the next year and a half, the group released the USB 1.0 specification on January 15, 1996.
What they came up with was a serial computer peripheral bus that used simple 4-pin connectors that were robust and inexpensive. USB allowed up to 12 megabit-per-second connections (enough for network applications at the time) and could serve up to 127 devices on a single bus if chained together using hubs.
Best of all, USB was completely plug-and-play, which meant that devices would automatically configure themselves (or look for suitable drivers) when you plugged them in. No more hassle with IRQs. And unlike previous standards, USB supported hot-swapping, which meant you could plug in and unplug peripherals while the computer was still on: no need to reboot when changing something as simple as your mouse.
At the time, the industry was also looking at competing standards such as Firewire (IEEE 1394), Apple GeoPort, ACCESS.bus and SCSI. But the simplicity and flexibility of USB won out, especially when vendors showed that they could make relatively inexpensive USB chipsets for hubs and peripherals.
USB appears in the wild
The PC industry was slow to adopt USB at first, with incremental improvements to the standard occurring over several years before it was widely adopted. Microsoft first supported USB in Windows 95 OSR 2.1 in August 1997 (and Win NT around that time).
According to ComputerWorld, the Unisys Aquanta DX desktop, announced on May 13, 1996, was the first PC to be announced with built-in USB ports, although other vendors such as IBM may have beaten them in the market. Reports in Byte Magazine say USB chipsets were not available at scale until mid-1996. Still, by the end of 1996, nearly a dozen PC vendors had announced PCs with USB ports – usually two ports per machine.
Even with some early support for USB from PC manufacturers, there were few USB peripherals that could use the ports until about 1998. Until then, nearly every PC shipped with legacy ports, so manufacturers continued to develop and selling devices that used them.
One event drastically changed the availability of USB peripherals. In August 1998, Apple released the iMac, a sleek all-in-one machine that gave away all of its legacy ports for USB. For the first time in more than a decade, Apple had created a machine without SCSI, ADB, or serial ports, and Mac peripheral manufacturers were forced to make a significant shift to USB.
While Apple can’t claim the sole credit in popularizing USB (there’s a healthy debate about that on StackExchange), the heavy press focus on the iMac’s reliance on USB first brought the port widely into popular consciousness.
Soon, those Mac USB peripherals were also available for PCs with USB, and with healthy support for USB in Windows 98, cheaper chipsets, and revisions to the USB standard, the PC market started to take over USB with enthusiasm around the dawn of the 2000s. Eventually, cell phones began to support USB connections, and the popularity of USB has not slowed since then.
USB over the years
Since 1996, USB has expanded enormously in capacity, including support for newer, smaller connector types and much faster speeds. The standard is always maintained by the USB Implementers Forum (USB-IF). Here are some of the highlights.
- USB 1.0 (1996): The formal introduction of the USB standard with Type A and Type B connectors. High speed is 12 megabits / second, low speed is 1.5 megabits / second.
- USB 1.1 (1998): This release fixed bugs in the 1.0 standard, including issues with USB hubs, and became the first widely accepted USB standard. It also introduced USB Mini Type A and B connectors.
- USB 2.0 (2001): This introduced a new, higher speed 480 megabit / second mode while maintaining backward compatibility with USB 1.1 devices. A 2007 revision introduced USB Micro connectors for the first time.
- USB 3.0 (2011): The 3.0 standard introduced a new 5 gigabits / second data rate called SuperSpeed. It also introduced new Type A, Type B and Micro connectors with more pins to support the higher data rate.
- USB 3.1 (2014): This increased the USB data rate to 10 gigabits / second. About this time, the USB-IF also introduced the symmetrical USB-C connector, which plugs in both ways and still works. (No more turning your USB device over three times to find the correct alignment!)
- USB 3.2 (2017): With this revision, USB climbed to 20 gigabits / second and obsolete the Type B and Micro connectors in favor of Type C.
- USB 4.0 (2019): This standard is Thunderbolt 3 compatible and supports connections up to 40 gigabits / second. All connectors except USB-C are obsolete.
The future is USB
As of 2021, USB will still work well, with so much support that USB connectors have become de facto outlets for charging smartphones, tablets, video game controllers, battery-powered children’s toys, and for novelties such as coffee mug warmers and a small desktop. vacuum cleaners.
USB hasn’t stopped improving. USB4 shows that the industry is serious about keeping the standard competitive as computers get faster and the data we shuffle between devices gets bigger and bigger.
In fact, it’s making progress – Apple’s iPad Pro tablets ditched their own Lightning ports for USB-C, although Lightning still exists on the iPhone and many other Apple devices.
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