Next, I will go over each of the connectors in brief detail. Below are the connectors you should be familiar with:
Serial (DB-9)
The serial connection commonly is referred to as the COM port connection. In Windows or DOS, Serial translates to COM1, COM2, and so on. Serial ports utilize the RS-232 standard. They have 9 pins in most cases but sometimes have 25 as well. The serial connector on your PC is male, while the serial connector on the device is female (obviously). The serial connector on your PC is the only male connector on most PC’s. The UART chip is truly what controls the serial port, as it translates serial data into parallel data and back into serial data once again. The serial connection transfers data asynchronously.
Parallel (DB-25 or Centronics)
Most of the time, the parallel connection is associated with LPT1 or LPT2 in Windows and DOS. It uses a 25 pin connector in most cases and sometimes uses a 36 pin Centronics connector. It is usually the largest connector on a computer. The standard is referred to as IEEE-1284.
PS/2 (DIN-6)
The PS/2 ports are well-known by most as the connectors used to connect keyboards and mice. You must plug your keyboard and mouse into the correct corresponding PS/2 connector (i.e. the keyboard into the keyboard connector and the mouse into the mouse connector) in order to use those devices. The PS/2′s connector is known as a DIN-6, and is a small circular connector with six pins.
DIN-5
You most likely remember the DIN-5 connectors as the large, old connectors on large, old computers. They have five pins, are larger than PS/2 connectors, and can only be used to connect a keyboard to a computer. Most modern computers no longer use this connection.
USB
There are now two standards of USB that are common place – the older 1.1 and the newer and faster 2.0. Both standards utilize the same connectors. They are rectangular and thin. USB is now a very common technology on PC’s. USB 2 devices can be used with USB 1 hubs and USB 1 devices can be used with USB 2 hubs – they simply operate at the lower speed together. USB is an asynchronous data transfer mechanism.
IEEE 1394 (Firewire)
IEEE 1394, or Firewire, is an asynchronous connection that transfers large amounts of data at high speeds. The connector is unique in shape. More power flows through Firewire than through USB, per se.
VGA (DB-15)
Although newer monitors utilize the DVI connection, the majority of modern monitors and video cards utilize the DB-15 connectors for the VGA connection. The VGA connection is used to connect monitors to video cards, which can be found onboard or otherwise. DB-15 connectors have 15 pins and are female on the computer end.
There are also other connectors you may want to personally familiarize yourself with, such as SCSI, Minijack, RJ-45, RJ-11, and PC power connectors. However, in the interest of brevity, I believe that the majority of people are familiar enough with these connectors or that they will not (in the case of SCSI) show up on the test in all likelihood. Next, we shall move on to Bus technologies in PC’s.
What is a bus?
An expansion bus is another word for an interface on your motherboard’s IO operations. Perhaps you have installed a new “AGP” video card or a new “PCI” sound card or replaced an old “ISA” modem. All of these acronyms stand for different names of buses commonly referenced by everything from instructional videos to manuals to your fellow computer professionals. Knowledge of the basics of these buses is important.
ISA
The oldest bus you will need to know of for the A+ exam is the ISA Bus. It is generally found on older motherboards, as newer ones typically do not include this connection slot. It is a 16-bit bus. It runs at 8 or 8.33 MHz. and is archaic by today’s standards. On older motherboards, it is the longest slot and consists of two groupings of pins – one to the left, which is larger, and a second to the right, which is smaller. This keys, or specially fits in, any expansion card. ISA stands for “Industry Standard Architecture” though it is no longer the industry standard.
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