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.
I used zip drives with both SCSI and Parallel printer interfaces.
I made my own null modem cables
I had gender changers and 9 to 25 pin adapters.
I even did a custom serial cable for my HP48
I lived a dangerous life full of connector bullshit and now I can't even get the USB connector at the first try.
you don't yearn for that old clog of wires, you dinosaur.
We still use most of those...
Good ol' RS-232 and RS-4xx are still used in industrial automation. Programmers love to talk about mainframe computers running on software written in COBOL, but the world of Automation is also filled with ancient relics, still running like they've done for the past decades.
Why does he pronounce AT as "at"?