Understanding PATA – CompTIA A+ 220-801: 1.5

| October 3, 2012


The Parallel ATA interface standard is one of the most common legacy hard drive connection types. In this video, you’ll learn how to configure and connect PATA drives to your motherboard.

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If you’re working with an older computer and you’re connecting up storage devices inside of those legacy machines, you may run into an interface type called PATA. It stands for Parallel AT Attachment. That AT attachment is really referring to one of the early models of computers from IBM called the AT, and that AT name has stock all the way through these attachment types for the storage we will put inside of those devices.

This Parallel AT Attachment, or PATA standard, is one that has been around for quite some time, since 1999 or somewhere around there. It really originated with a completely different name. It was called Integrated Drive Electronics. It was created by Western Digital. That was the standard that they created for this. At the time, there weren’t a lot of other options out there, and Western Digital became very popular.

And so we started to see this interface everywhere. A second generation that was even called EIDE for enhanced IDE. And ultimately, the standard was picked up and used by everyone. PATA changed quite a bit through the years. We saw faster and faster speeds come out of PATA. We started with 16 megabytes per second, and the standard went as high as 133 megabytes per second, as well as adding other devices.

Not just hard drives, but we were connecting up other peripheral components to that ATA interface. If you’re connecting up a PATA storage device inside of your computer, you’ll probably be using a 40-wire cable or an 80-wire cable. On both of these cables, we have a connection to the motherboard on one side, and on the other side are two other connections.

You can plug in two storage devices to a single PATA interface inside of your computer. This older 40-wire connection was one where we put what we called the master or device 0 device on the connection that’s closest to the motherboard, and the connection that’s furthest away from the motherboard we called the slave connection.

Now, these two storage devices did not compete with each other. It was just a naming convention. And we’ve updated the standards to use device 0 and device 1 to describe those two storage devices, because they don’t use or count on each other being there at all. As we needed additional speed through these PATA connections, we began to use these 80-wire cables.

These 80-wire cables allowed us an enhanced amount of throughput, but you’ll notice we changed where we put these default devices. A device 0 now went at the end of the cable, and the device 1 went right into the middle. And of course, your motherboard connection on the other side is exactly the same. Same number of pins.

When it’s connecting up, you can see the connections themselves are identical. The big difference between were the additional cables put inside of this 80-wire connection. And those wires allowed us some additional throughput. If you look at the cables very closely, you can see the 40-wire or 40 conductor cable has exactly the same type of connection as the 80 conductor cable.

The difference is the number of wires in between. Those additional 40 wires on the 40-wire cable are ground wires. They helped prevent crosstalk and enhanced and improved the amount of throughput that we could get through an ATA connection. The PATA interface on the motherboard was relatively large. You could really see it. In fact, you may even see it called IDE on certain motherboards.

It may be called ATA using the older terminology. The newest terminology would be PATA. And it has these pins here. You can see there was even a pin missing right here because on the cable there is a key for that. That way, you’re not able to plug this cable in the wrong way. It has to plug in this connection, because it won’t fit because that pin is filled in on the cable itself.

So if you’re in the dark or you’re trying to get it onto a motherboard and it’s a difficult connection, you can almost feel your way around. And if it goes in, you know that it has gone in the right way. There’s no way to plug it in improperly. On the drive itself, that PATA connection, pretty large. We can see that it looks very similar to the connection that was on the motherboard.

There are almost always jumpers also on the back of the hard drive. We’ll look at what those are used for in a moment. And there’s probably a four pin connection just for some power so we can power up this drive and get everything running. So you’ll very commonly have your big ribbon cable connected to your drive in the back, and you’ll have another power cable plugging into the four pin connection.

If you were to compare a PATA cable and a SATA cable, you would see a dramatic difference between the two. The older PATA ribbon type of cable is one that is very wide, has a lot of pins associated with it, there’s usually a color down one side of it that usually designates pin 1 on the connection so that you have a point of reference if you’re plugging it into your motherboard.

But the SATA connection, much smaller, but supports much faster throughputs. You can see why we would want to use that over this larger connection, not only for the ease of use and easy connection inside of your computer, but it takes up so much less space and allows for better air flow through your computer.

I mentioned earlier that we were using the PATA connections for more than just hard drives, and this is a really good example of this. This is a CD-ROM drive. And a CD-ROM drive originally didn’t have a standard way to plug in to your computer. We generally used SCSI type of connectivity or some other proprietary method to plug in the CD-ROM drives.

We came up with a standard called the ATA Packet Interface, which allowed us to plug in these connections via this IDE or via this PATA connection, and it was able to communicate through the PATA connection as if it was a hard drive. So although that PATA standard was really designed for hard drives, we were able to use the same protocol, the same communication method to also plug in many other kinds of devices.

If you look closely on a hard drive, you’ll probably see printed on the drive itself some documentation. On this Quantum drive, you can even see where those particular jumper settings are and what they mean. If we were to look closer on this, we would see that there’s a jumper setting that we would set right here for DS. That sets it for the master connection, which is the factory default.

That means this drive will be the master. We’ve designated this to be the master on the PATA connection. If you use this particular jumper, you’re designating this particular drive to be a slave connection. Much more commonly, we would set this jumper here for cable select. That means that depending on where you plug the drive on the cable, it will determine whether it is the master or the slave.

If you remember the picture of those cables that we were looking at earlier, certain interfaces were designated as the master and certain interfaces were designated as the slave. By using this cable select jumper then, we’re able to tell our computer to simply look on the cable, determine where the drive happens to be plugged in, and if the drive is set for cable select, it will simply use that as the device 0 or device 1 depending on where it happens to be on the cable.

Here’s a good example of what you would expect if you were to plug-in a PATA connection. You’ve got your long ribbon cable. It’s got the connection to the motherboard. And then you’ve got one connection that’s plugged into the drive. And here’s this other connection to the side. Because this one happens to be a 40-pin cable, this first connection that is closest to the motherboard is considered the device 0 or the master connection.

And if we had another storage device, we could even plug it into this connection. It’s going to sit empty in this scenario. It would be the device 1 or the slave connection. And if we’d set this to cable select, wherever we plugged it in, that’s where the interface would be defined inside of our computer.

We could also set this to be the master connection and plug it into that master link and also have it synchronize up as well. The PATA connections aren’t ones that we commonly see any longer, but if you’ll be working on an older computer, you’ll most certainly see these ribbon cables and these older PATA connections.

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Category: CompTIA A+ 220-801

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