The magazine of the Melbourne PC User Group
Installing the USB Ports You Didn't Know You Had
John McNabb

If you think you do not have USB on your PC, this article is for you. If your computer is fairly new there is every possibility USB is sitting there, uninstalled, waiting for you to connect it. So, the message is Don't Sell Yet. You may already have considered upgrading because apparently your machine doesn't have USB? This article could save you the expense, especially if it seems like only yesterday that you spent all that money anyway.

You may be lucky. You might be able to simply purchase a low cost USB header, plug it in and start. On the other hand you may have to follow this article to conduct your own little investigation, establish exactly what, if any, USB capability is on your computer and determine how to connect to it. Either way, it's a useful learning exercise and the chances are you'll finish up knowing much more about your computer. After spending a considerable amount of time attending the East SIG Workshop it's time to spread my three cents worth of knowledge and experience to the members.

Why Would You Need USB?

There has always been a problem with the number of devices you can connect to your PC. In the early days of the 8-bit XT computers (8086 & 8088 CPUs) there were only eight IRQs (hardware interrupts) available. This meant that you could have only eight devices. The 16-bit AT computers improved on that introducing 16 IRQs, and then there was USB. Universal Serial Bus (see PC Update, July and August 2000) has given us the capability of connecting up to 127 devices to a single PC and avoid the need for rebooting one's computer each time a new device is attached. The alternative of course is SCSI but that's more expensive and the subject of another article.

Many New PCs Already Have USB Built-in


Figure 1. USB already installed on an ATX motherboard

 Most of the very new ATX style motherboards have the full USB sockets on them and they point through the case (Figure 1). If your machine has one of these you don't need to read any further, although you may have to enable USB in your BIOS settings. If you purchased a PC with Windows software installed and running, this may have already been done. If not, see "Enabling USB in the BIOS settings" later in this article.

If your machine doesn't have the ATX style motherboard, you must determine whether your particular motherboard has USB capability. 

Most AT style motherboards made in the last three years have a USB port connector on them, although many of them did not have that USB capability installed at the time the PC was assembled. The documentation that came with your motherboard should tell you whether or not the capability exists and if so, it should also identify the connector pins and show their location. If not, turn off your machine, take off the cover and check it out. Look around near the location of the serial and parallel ports and look for two rows of four or five pins. It could be like mine, two rows of five pins found snuggled in between two PCI slots (figure 2) and identified by a "J" number or they could be marked USB1 and USB2.


Figure 2. On my machine the USB pins were snuggled in between two PCI slots and labelled J14. Identification was 
only possible from the motherboard documentation.


Figure 3. Two rows of USB pins on another motherboard. 
These are located at the edge of the board near the 
keyboard plug and clearly labelled USB. (See also Figure 3a)

If you find them you are in luck. Figure 3 shows the two rows of USB pins on another motherboard. These are located near the edge of the board and are clearly labelled USB. The same picture taken from a different angle (Figure 3a) shows how the Pin No 1 end is clearly identified and you can also see the two rows of COM Port pins nearby, where the COM header would be plugged in. Not all motherboards are made like this, with ease of assembly considered.


Figure 3a. This view shows the Pin No 1 end clearly identified. On this motherboard a "double" USB header could be used because the No 1 pins are at the same end.


Figure 4. Representation of the Pin-out chart supplied for my USB connections. Note the Vcc (5-volt supply) pins shown at opposite ends.


Figure 5. The connections to a four-pin set.

Beware!

When you find them, it is very important that you determine which way these pins are conferred. Usually this can be found in the information that came with the motherboard. Did I hear somebody say they threw that material away? You should not open the top of your computer! In my case there was a CD-ROM that came with the system and it contained a detailed list of all the connectors and jumper settings with diagrams. I simply printed it out (see Figure 4). I was lucky I kept that CD but finding it was another thing. 

As mentioned, your motherboard could have two rows of four or five pins. Figure 5 shows the connections to a four-pin set. If/when there is a Pin No 5 it will be for the shielded cable. This is not always used because often the shield is connected to Pin No 4. Note also your motherboard may have seven pins (with a common ground) as with "Soyo" brand , or some other setup. If so, you will need to purchase their proprietary Header.

Before Buying the USB Header

It is very important that you do not plug in the header the wrong way around. That would cause a short circuit on the 5-volt pin (Pin No 1) to ground and damage your motherboard. There are three scenarios here and it is extremely important that you determine how your motherboard was built. One is where the two rows of pins are conferred facing the same end (as in Figure 3a), the next (as with mine) is where Pin No 1, the 5-volt supply pins, are at opposite ends (Figure 4), and finally you may have a proprietary setup. 

If you have to buy a plain label header it is best to get one with separate 4-pin plugs (Figure 6) although if you find the pins on your motherboard are suitably conferred, and clearly labelled as in Figure 3a, you will be able to use a 5-pin double header (Figure 7). Naturally it's wise to know which is needed before purchasing your header. If you can't avoid it (or simply can't wait to get started), buy the one with separate 4-pin plugs. Prices range from $8 to $15 at swap meets.
 


Figure 6. USB connector with separate 4-pin plugs, 
caters for the situation like mine where the motherboard 
may have Pin 1 at opposite ends.


Figure 8. The usual colour codes.


Figure 7. USB header with the double 5-pin plug. Caters 
for where on the motherboard both No 1 pins are at the 
same end.


Figure 9. Screwing in the USB Header Bracket

If you have an older computer with a fancy, round USB plug (like a PS2 plug) then forget it. Check that you have a spare PCI slot, buy a PCI USB card for about $50 to $60 and remember that Win 98 SE is the minimum operating system you should be using. 

If you are in any doubt about which is Pin No 1 in each row you must determine that before proceeding. If you are handy with the tools and you have a DIGITAL multimeter you will be able to test the pins at each end to determine which is the 5-volt Pin 1. If not, take your computer to a technician and ask for this to be established.

Plugging It In (Colour Codes)

Usually the colour code of the wires on the header plugs are as per Figure 8 with the red wire attaching to pin No 1, but if you have the motherboard documentation, check it anyway.

When you know which way to plug in the USB headers, attach the headers, remove the metal strip from one of the slot positions in your case and screw in the USB Header Bracket (figure 9), assemble your machine and the job is complete. Check the BIOS settings and you're away.

Enabling USB in the BIOS settings

You may have to enable USB in your BIOS. Firstly go into BIOS settings. This is usually achieved by pressing the DEL key during boot up. Check if USB is there and if so, enable it. 

Be very careful to NOT change anything else accidently and certainly don't change anything just for the sake of it. You may render your computer inoperable. If you change anything in the BIOS you must know exactly what you are changing and why. Save the new settings and exit.

All this information took me about a year to find out so that I could take advantage of my USB. But it was worth it, in the end. You can learn about these things, and more, at the East SIG Workshop meetings on the Sunday after the East SIG meeting.

Reprinted from the April 2001 issue of PC Update, the magazine of Melbourne PC User Group, Australia