Computer Interface Speeds and Distances – CompTIA A+ 220-901 – 1.7

| December 3, 2015

We use many different cables and connectors with our computers. In this video, you’ll learn about some of the most popular interface speeds and distances.

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There are three different versions of USB that you need to know for your A+ exam. Version 1.1 was the first big release of USB. It was one that ran at two different speeds there was a low speed and a full speed. The low speed was 1 1/2 megabits per second. And you could have a cable that was about three meters long. The full speed ran at 12 megabits per second. And that standard allowed us to have cables that were at least five meters in length.

The update to the USB 1.1 standard was the USB 2.0 standard. It allowed us to have greatly increased speeds at 480 megabits per second, and again, keeping that five meter length of cable.

One of the newer standards of USB has been USB 3.0. This is also called SuperSpeed USB, probably because we are able to get five gigabits per second of speed from a USB 3.0 interface. And the maximum cable length we can have with USB 3.0 is about three meters long.

Here’s the connectors that you’ll see used with USB 1.1 or USB 2.0 devices. These are exactly the same physical types for both of those USB standards. A Standard-A plug is what you will find connecting to a laptop or desktop computer. And these other connectors are commonly used to connect the devices to our computer. Standard-B plug is a very large connector relative to the others. You can see it’s almost square in shape. And if you have a mobile device, it’s probably using these much smaller connectors with the Mini-B plug or the Micro-B plug connection.

Here are the USB 3.0 connectors. And you can see the Standard-A plug on USB 3.0 looks almost identical to the previous versions of USB. And it’s designed to be backwards compatible with those versions. However, the 3.0 plug here has additional pins on the inside and is specifically designed to use the high speed 3.0 when connecting to a 3.0 USB interface.

You can see the other connectors have changed a little bit. The USB Standard-B plug has that similar square connection to the previous versions, but you can see it does take a little bit of a different shape. And the tinier plug that you would commonly see connected to mobile devices might be this USB 3.0 Micro-B plug. And you can see it uses a little bit of a different set of connectors and pin outs than the standard USB 1.1 2.0 Micro-B plug.

Another interface type you might see is the FireWire interface. This is formally called the IEEE 1394 standard. The term FireWire is one that is an Apple trademark. And it became very popular because Apple was one of the first companies to provide FireWire interfaces on their hardware.

But there are many other devices from many other companies that use this same standard. But you probably won’t see it called FireWire. It may have a connector that says IEEE 1394. That’s a very literal name for the connector. Other companies have used other terms like i.Link or Lynx. All of those are exactly the same interface running exactly the same standard. And you can of course connect an Apple FireWire interface with another company’s IEEE 1394 or iLink interface, and they are absolutely compatible with each other.

One of the interesting capabilities of FireWire is that allows you to daisy chain devices together if the hardware has multiple ports that allows you to do so. You just have to make sure that of the 63 maximum devices that you can daisy chain, that you don’t exceed the length between them by more than 4 1/2 meters, or 15 feet, as a limitation on each individual link.

There are generally two types of FireWire connectors that you’ll see. One is the FireWire 400. This is also called the Alpha mode FireWire. And it is specifically the IEEE 1394a standard. This supported speeds of 100, 200, or 400 megabits per second in a half-duplex mode.

You also see FireWire running at a faster speed called FireWire 800. This is also referred to as Beta mode. And you might see it referred to as IEEE 1394b. This doubled the maximum speed of the FireWire 400 and it also allowed us to run that 800 megabits per second in full duplex mode. You can also see that some devices will have optical connectors using FireWire 800, and that allowed them to support distances up to 100 meters between devices.

Here’s a picture that better shows some of these interfaces you might see on FireWire. I’ve also included a standard USB Type A plug here on the left side. So you can really see the relative size across all of these different FireWire cables. The FireWire 400 is both the 4-pin and the 6-pin version that you see here in the middle. The 6-pin version allows you to send power through the FireWire cable, so that remote device may not necessarily require any extra power source. You can also use this 4-pin FireWire that’s sending exactly the same FireWire signal, but it doesn’t include the power connectors. And if you’re using faster equipment it may be using this 9-pin FireWire Beta that runs at 800 megabits per second.

This is the back of an external storage array that uses a number of these different interface types. And you can really see the differences between them. These on the left are USB connectors, both the Type-A and a USB 2.0 Type-B connector. These next three connectors are the FireWire connectors. You can see a FireWire 400 connector and a FireWire 800 connectors next to that. Notice it has an S next to it to designate that that is the speed of the FireWire interface.

If you’re working with storage devices these days, you’ll probably be connecting to a SATA interface. SATA stands for Serial AT Attachment. And there are a number of different versions of SATA that you’ll find.

The first release of SATA was SATA version 1.0. And it allowed me to have SATA connectivity at 1.5 gigabits per second and a cable length of about a meter. The next release of SATA was SATA Revision 2.0. This doubled the speed up to three gigabits per second, and still had that one meter maximum cable length. The next version was SATA Revision 3.0. And it again doubled the speed of the SATA connection to six gigabits per second over that one meter cable.

You might also see an external SATA connection called eSATA. Generally, the eSATA connectivity is going to match the SATA being used in that particular device. So if it’s running SATA Revision 2.0, the eSATA is also going to run at exactly the same speeds as the SATA Revision 2.0. You can also see that eSATA supports a maximum cable length of about two meters. That becomes very useful when you’re connecting to devices that are on the outside of your computer.

Here’s a hard drive that has SATA interfaces on it. You can see the two interfaces on the left side. This smaller interface is the data connector. One of the advantages of using a serial device is that it only uses a little bit of room to send the data. And it’s only seven pins that it needs for that data connection.

SATA power connection is 15 pins. You can see it’s a little bit of a larger interface. This particular hard drive also supports power over a traditional Molex connector. So it depends on what power supply you have inside of your computer. This particular hard drive will support power over either the SATA 15-pin connector or the Molex connection.

There are many different kinds of video connectors for your computer and one of the most popular through the years has been the Video Graphics Array connector, or VGA. The VGA interface is a 15-pin connector. You can see the pins inside this. And it’s connecting using this D-Shell connector. We call this a DB-15 connector. Although the actual shell size is a DE, we will always see it listed in our literature as a DB connector. This also has a very standard blue color associated with it. We’ve standardized VGA on blue based on an international standard from the PC System Design Guide.

These VGA connections send analog signal only. They don’t send any digital signal over this connector. So you will find that as the signal degrades, it’ll become fuzzy and more difficult to see on the screen. That’s why you can generally get a length of about five to 10 meters before you can visually start seeing the image itself look worse and worse.

One of the newer kinds of video connectors is the HDMI connector. It stands for High Definition Multimedia Interface. This is an all-digital connection. There’s no analog signal being sent over an HDMI cable. And you’re able to send both audio and video over this single link. Because this is a digital connection, we’re able to extend the cable until we finally will lose so much data that we’re not able to see the video or hear the audio signal anymore. And you can usually get about 20 meters of distance before you lose so much signal that you can’t see anything on the other side.

You’ll generally run into two different kinds of HDMI connectors. One of the more common, and the larger connector, is the 19-pin Type A connector that you see right here at the top. This is a proprietary connection type. It’s not one that you can get from anywhere else. Whenever you see this connector, it is very clearly an HDMI connection. For smaller devices, like cameras or mobile devices, you might use this much smaller miniHDMI. This is technically a Type C connector and it’s one that takes up much less space than the larger HDMI Type A connector.

A third common video type you may run into is the DVI– the Digital Visual Interface connector. There are two different kinds of connections to DVI. There’s a single link and a dual link connection. The single link supports 3.7 gigabits per second of throughput, which means we can see an HDMI signal at 60 frames per second. The dual link supports larger resolutions or faster frame rates because we can get 7.4 gigabits of throughput through a dual link DVI connector.

The DVI interface will send out analog signals, digital signals, or a combination of analog and digital. It just depends on the type of interface you have on the hardware you’re using, and how you’re connecting to that with the interfaces on the back of that device.

Here’s a common DVI connector that you’ll see. This is a DVI-D single link interface. So this will send digital signals, generally to a single output. If you’re connecting up a single monitor to a computer and you’re using standard HD resolutions, then you’re probably using a DVI-D single link cabling connector.

On our computers, we need more than just video of course. We also need audio connectivity. And if you’re connecting up analog audio then you’re probably using a TRS plug. It stands for Tip, Ring, and Sleeve. And you’ll see two different types of TRS. One is a quarter inch and one is an eighth inch. You may see this listed as 6.35 millimeters for the quarter inch, or 3 1/2 millimeters for the eighth inch TRS connection.

You’ll sometimes also see different colors on the back of your computer for the different TRS connections. But there’s no real standard that everyone follows with these. So you have to look very carefully at where you’re plugging in these TRS connections.

For digital audio we might use a TOSLINK connector. This stands for Toshiba Link and it is an optical fiber connection. We’ve been using this for a number of years. It was created in 1993. And you’ll see it not only on computers but many other types of consumer electronics as well. Because it is fiber, we are able to extend it, but it doesn’t support very long distances. We can go a maximum of about 10 meters, or 33 feet, with something like a TOSLINK audio connection.

Here are a number of TRS connectors that you’ll see on the back of this computer. And you can see that relative to the USB connections and the RJ45 network connection, it has a very small size associated with it. These are colored in different ways so that you’ll know which speaker to plug into. This may support both left and right front, left and right back. You may be able to plug in a center channel, or even a microphone, using these TRS connections.

If your computer has an analog modem, or you’re connecting to a DSL connection, then you’re probably using an RJ11 connection. This RJ11 stands for Registered Jack number 11, and it’s almost always this telephone type connection.

This is what we call a 6P2C connector, which means there are six positions on the connector. But we’re really only using two conductors inside of it. If you look very closely at this RJ11 jack, they don’t even include any other conductors. You can see the single two copper conductors inside the jack.

Some other RJ standards use a same size as this connector, but use different numbers of wires or connectors. You can see, for instance, a 6P4 conductor or 6P6 conductor, but if you’re ever using an RJ11 for telephone purposes, it’s always going to be this 6P2C.

Here’s a close up of an RJ11 connector and you can see there are six different positions where you would be able to fit conductors. We’re of course only using the two center conductors for our analog modems and our DSL connections. Although it’s very common to see RJ11 cables wired with all four wires inside the connector.

The other common RJ connector type you’ll use is an RJ45. This is used primarily for ethernet, for your patch cables, your crossover cables, and anything else that’s using copper ethernet connectivity. This is an RJ45, again, Registered Jack number 45. And it has a similar type of modular connector as the RJ11. But the connector is a little bit different. This connector is an 8P8C, which means there are eight positions. So it’s a little bit larger than the RJ11. And we use all eight conductors inside of this cable.

Here’s both an RJ11 and an RJ45 next to each other. This ADSL connection is an RJ11 and the ethernet connection to the right is an RJ45. And you can see they almost look identical. But the ethernet is a little bit larger. If you tried to squeeze the ethernet cable into this ADSL connection, it simply won’t fit. Unfortunately, you are able to plug an RJ11 into an RJ45, so you want to be very careful what you’re plugging in to what interface on the back of these devices.

One of the latest connector technologies out there is Thunderbolt. This is a very high-speed serial connection used to connect your computer to other peripheral devices. It allows you have data and power on the same cable. And as you can see, the interface looks exactly like a Mini DisplayPort connection. And that’s because it’s using exactly the same interface as a Mini DisplayPort standard.

This throughput though on Thunderbolt is very different. Instead of having just Mini DisplayPort for video, we can send many types of data over this connection. And Thunderbolt version one supports 10 gigabits per channel. And we can have two channels for a total of 20 gigabits of total throughput on Thunderbolt version one. Thunderbolt version two increased the speed to 20 gigabit per second, aggregated across all of the channels, and Thunderbolt version 3.0 provides a total throughput of 40 gigabits per second.

The Thunderbolt standard supports a maximum cable length for copper of three meters and I can get up to 60 meters of a maximum length over an optical connection. I can also daisy chain multiple devices together– up to six different devices on these Thunderbolt connections.

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Category: CompTIA A+ 220-901

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