We practically connect everything by USB these days.
Keyboards, mice, speakers, phones, even mini consoles are powered by USB.
But what did we do before this miraculous connection became common place?
Well, that's what I'm here to explain.
USB, otherwise known as Universal Serial Bus was designed by a consortium of manufacturers
way back in January 1996, with the intention to standardise the connection of computer
peripherals, which at that point used a number of different methods dating all the way back
to the original IBM Personal Computer.
Well, I say dating back to, but almost all of these standards were already established,
such as the parallel port by Centronics in the 1970s and the RS-232 port in 1960 by the
Electronic Industries Association, but we'll get to those in a bit
some of these standards, such as IEE1284 developed by Centronics for parallel communication,
were introduced before the IBM PC, but its IBM's adoption which solidified their use.
Released in August 1981, the IBM Personal Computer was assembled from many off the shelf
OEM parts, incorporating a custom BIOS, but with the remainder made up from mostly external
manufacturers.
To connect the keyboard, a 5 pin DIN socket was chosen, a connection somewhat standardised
in computing during the early 1970s by the Deutsches Institut fur Normung.
This connection was rugged, provided ample shielding and was typically the only connector
to be soldered directly to the motherboard, although early machines also included a cassette
port, again a din socket, as a low cost method of loading software, common on home computers
of the time.
This meant peripherals such as a mouse, printer, modem or even the monitor needed to be connected
through expansion cards.
These expansion cards plugged into 8 bit expansion slots on the motherboard, which would go on
to be called the Industry Standard Architecture, or ISA slots.
This name was adopted because the IBM PC spawned many a'clones, after all, once the BIOS was
reverse engineered, or copied through observation, the other components could be bought from
external parties, and soon the IBM PC Compatible market was born, and awash with machines.
The IBM PC model would evolve into the more powerful AT machine, with the clones of course
following suit, but across all these machines, you would typically find a video card, for
plugging your monitor into, a serial card, offering one or two serial or communications
or RS-232 ports, and a parallel card, although this was often combined with the serial card.
Original IBM machines had slightly different connections, but this is the typical setup
the IBM PC would evolve into.
So, we've got the basics connected, but what about everything else?
Well, let's start with the mouse.
You could connect that to a serial port.
Your computer identifies these as COM ports, and usually your mouse would have a 9 pin
serial connection.
Plug it in, install a mouse driver into your operating system of choice, and you have a
magical on screen cursor.
If you didn't have a 9 pin serial port, you could always use a an adaptor, and plug your
mouse into a 25 pin serial port.
This was the original serial port design, with the 9 pin introduced by the IBM-AT model
and offering a reduced size, more cost efficient connection using a subset of the full serial
port standard.
For most devices this connection was more than sufficient, although it's design means
it can easily be confused with a DB9 joystick connection, as seen on the Sega Mega Drive
for example.
If you wanted to connect a device such as a modem, then you're likely to require a full
25 pin port, featuring the full serial port specification.
Many, and indeed, most, devices could be connected via serial port, but the main issue here was
speed.
The clue is in the title, as data is sent in a single stream, rather than concurrently
with the maximum speed usually 115,200 bits per second.
It can go higher depending on hardware, but was generally unsupported by most software
in any case.
So what about the parallel port, or Centrionics parallel port more specifically?
Well, although the original ports could only muster 150kbits/s, later enhanced & extended
parallel ports could handle up to a whopping 2.5MB per second.
Unlike most serial port applications, data is sent concurrently across several of the
25 pins, making it an ideal choice for printers and even devices demanding high speed such
as ZIP drives and other storage device, which take advantage of the bi-directional modes
on later enhanced ports.
But this parallel communication had it's own problems.
The main being that the 8 data lines needed to be synchronised with each other.
So shoving 8 bits faster and faster down these pins could cause some synchronisation issues,
limiting transmission rates.
USB for example, uses serial communication, but with technology allowing far greater speed
transfer than our faithful serial connections could go.
Of course, this technology also allows us to have many usb ports and even additional
hubs, but going back to our serial and parallel ports, your typical computer might only have
one of each.
The problem is of course, what if you wanted to connect something else?
All your ports are gone.
Well, during 1987, IBM stepped in again and launched the PS/2 connection.
This did away with the bulky keyboard DIN port whilst at the same time, giving your
mouse, it's own dedicated connection.
However, this implementation wasn't wide-spread.
In fact, it was designed to be the opposite.
IBM were fed up with competitors stealing a market they essentially created, and so
in April 1987 launched the IBM Personal System/2.
This range was designed to replace their previous models, and as part of the parcel had proprietary
architecture, part of which were the PS/2 ports.
They keyboard interface was electronically identical to the AT interface, with with a
smaller 6 pin mini-DIN.
The BIOS also added routines for the dedicated mouse port.
The range wasn't massively successful, but the dedicated ports did catch on and would
begin appearing on rival machines throughout the 90s.
They were particularly useful for laptops (for example), which couldn't always accommodate
larger ports.
Just to throw an extra layer of complication in.
Microsoft also had their own mouse port design, known as the "Microsoft InPort".
This port was typically provided by an 8 bit ISA card and provided a mini-DIN port, similar
to those found on PS/2 machines, but with a 9 pin design.
But again, this was another plug in card, when expansion space may have been at a premium.
Thankfully change was coming.
Although it was common at the time to have separate plug in cards to manage these ports,
including some obscure ones such as this all in one Tandy adapter, from this point on it
started to become common to see COM and Parallel ports have their own header on the motherboard,
like this rather grubby example.
Reducing the need for expansion cards and beginning the transformation of packing most
connections directly onto the motherboard, as is common today.
OK, so we've got our printer hooked up, a modem for some sweet sweet Bulletin board,
or even early internet access and a mouse for gliding through Windows '95.
What about sound?
Well, that hasn't changed much at all.
Sound cards of the time typically had numerous 3.5m jack outputs and inputs, but as they
were scene as a gaming or multimedia accessory, they usually also had this.
This is a 15 pin game port.
It was originally introduced on the game control adaptor - a separate board for the IBM PC,
by the mid 80s, it was often added to serial or parallel expansion cards, but by 1989 found
its way onto the first Sound Blaster card, allowing the attachment of joysticks, but
also by making use of the redundant pins 12 and 15, allowed for a MIDI adaptor to be connected
as well.
The Sound Blaster quickly went on to be the most popular sound card, with many clones
following suit.
So with that, our PC is wired up and ready for action.
But this isn't the end of this story, there were a multitude of other ports that could
be brought into the mix, allowing for additional applications.
You could buy a SCSI controller to connect CD-ROM drives, scanners or even hard drives.
You could even buy a multitude of products requiring their own bespoke expansion cards,
meaning not only might you run out of slots, but also system resources.
It's with all this complexity which led to Compaq, DEC, IBM, Intel, Microsoft, NEC and
Nortel to get together in 1994 and have a good hard think.
Bespoke and incompatible connections wasn't in anyone's favour, and so in a great example
of companies working together to solve a problem representatives from each company were dispatched
with the goal of making it easier to connect external devices to PCs, whilst addressing
the restrictions and usability issues of the current methods.
One of the team members working on this was Ajay Bhatt, working at Intel, who then produced
the first USB integrated circuits in 1995.
This original specification had a standard data rate of 1.5MBit/s, up to 12Mbit/s, and
was supported by Microsoft Windows '95 Service pack 2, but it took a few years before USB
started to become standardised.
In September 1998, USB 1.1 was released, which had less timing and power limitations and
was adopted much quicker, with Microsoft describing this the "Legacy Free PC".
All iMac G3's also support USB 1.1.
Of course, given the still somewhat limited speed, USB 1.1 wasn't ideal for external storage
devices, even with file sizes which were typically much smaller compared to today's juggernauts.
For Apple users, this didn't really matter, they had Firewire, but for everyone else,
USB 2.0, launched in April 2000 was the point we caught up, offering a high speed mode of
480Mbit/s.
By now the ball was firmly rolling and PCs which may have had a nominal single USB port,
started having multiple ports front and back.
Legacy connections still hung around, but from about 2010 onwards, they've largely disappeared.
Since 2007, the USB Battery Charging release was implemented and with USB 3.0 appearing
in 2008, offering up to 5Gbits/s, pretty much all base were covered.
Which lands in the USB saturated world we currently know, and, appreciate.
For the most part.
USB has definitely made things a lot easier, and convenient, but I still yearn for the
mess of wires and connections from the 90s.
Finding male to female adaptors, sorting null modem serial cables from the standard ones,
networking up PCs with homemade cables to play Doom.
It was splendid, thankfully I can still get my kicks playing with old hardware.
The rest of us probably couldn't give a monkeys.