System Type

Current home computers use a Serial ATA interface, however computers that are more than a year old may have a Parallel ATA (also known as Ultra ATA or IDE) interface. The best way to determine which type of drive is required is to review the documentation that came with the computer, which should mention if the computer uses Serial ATA (SATA) or Parallel ATA. If the documentation is not available and you plan to perform the upgrade yourself, then the next best option is to look at the hard drive connectors on the motherboard. A Parallel ATA connector will have a ribbon cable (approximately 50 mm wide) with many ridges going between the drive and the motherboard. A Serial ATA connector will be a much thinner cable (approximately 8 mm wide). See images below for examples.

Parallel ATA (PATA) Drives

PATA models can be Ultra ATA/33, /66, or /100, and in some cases, Ultra ATA/133. These drives are all downward compatible with previous PATA interfaces and each will work in these slower modes as well as the mode it is designed for. The drive you choose will operate at the fastest mode that your computer's motherboard is capable of supporting. If you have an Ultra ATA/66, /100, or /133 controller, the 40-pin port on the hard drive controller will normally have a blue plastic shroud surrounding the pins. The cable for these modes has to be a 40-pin, 80-conductor ribbon cable, also called an Ultra ATA cable. If you have a Ultra ATA/33 or standard ATA (either IDE or EIDE) controller (for Pentium 3 computers or older), it will have either a black shroud surrounding the pins or no shroud at all. You can use a standard 40-pin, 40-conductor ATA cable with these types, or if you are not sure, the Ultra ATA cable will work with either and offers superior electrical performance.

Serial ATA (SATA) Drives

Serial ATA (SATA) hard drives are designed for easy installation. A SATA drive has its own dedicated data cable that connects directly to a SATA host adapter or a SATA port on your motherboard, and unlike Parallel ATA (PATA) drives, SATA drives do not need jumpers to be configured as a "slave" or "master".

First generation (SATA I) SATA drives have a burst transfer rate of 150 MB/sec (1.5 Gbit/sec) while second generation (SATA II) SATA drives have a burst rate of 300 MB/sec (3.0 Gbit/sec). The jumper block next to the SATA interface connector on a SATA 300MB/s drive can be used to force the drive into SATA 150MB/s mode for use with older SATA controllers that only support the 150MB/s burst rate.

You can use both SATA and PATA drives in the same system as long as both interface types are supported. Older computers may not have any SATA ports, in which case an add-on SATA host adapter (or controller) can be added in order to connect a SATA drive to it. This makes it easy to add SATA compatibility to your existing system without removing existing PATA disc drives.

SCSI Drives

You may additionally have a SCSI controller or you might only have a SCSI controller on your system. This controller is also sometimes called a host adapter. These SCSI controllers come in a variety of types, or SCSI revision levels. Each type has its own unique hard drive requirements:

• You could have a Narrow SCSI ribbon cable (approximately 61 mm wide) with a 50-pin controller and drive; this is recognized by the rectangular-shaped connector with two rows of 25 pins each coming out of the hard drive. 
• You could have a Wide SCSI ribbon cable (approximately 42 mm wide) with a 68-pin connector coming out of the hard drive. This is characterized by a trapezoidal "D" shaped female connector coming out of the hard drive. This could be a variety of different SCSI interfaces, including Fast SCSI-2 Wide, Ultra Wide, Ultra2 LVD, Ultra160 LVD (also called Ultra 3), or Ultra320 LVD. The drive model you need would depend on what hard drive controller you have. Each of these types uses an additional power supply connector on the hard drive.

Hot-Swappable SCSI

On some systems, known as hot-swappable computers, you have drives that would only have one connector for interfacing with the controller or motherboard. This is a single connector attachment, also called SCA or SCA2. The data and power connection are combined into one connector, which is 80-pin and trapezoidal, or "D" shaped. These models are designed to be connected to a tray or in a drive cage, and they simply slide into the front of the hot-swappable computer cabinet and push into a connector affixed to a backplane board in the rear of the computer case.

Apple Systems

If you have a Mac G5 computer or newer, your computer's motherboard supports SATA drives only; there is no connector for a PATA or SCSI drive.  Mac G4 computers usually have PATA (Ultra ATA 100) motherboards.

If you have an older Apple computer such as a G3 Mac or older, or an Apple-compatible computer, the drive model you require depends on the model of Apple computer you have. These will vary, and the drive you choose depends on the SCSI revision level or the PATA level your system is capable of using. Please consult with your Apple technician or dealer, or call our Drive Presales department at (877) 271-3285 for a clarification on what drive your Apple compatible system is capable of using.

If you are still unclear on what model your system requires, try to get all the information you can about your current setup, such as the model number and manufacturer of your current hard drive, the approximate capacity of your current hard drive, the computer manufacturer, and possibly the model of the computer.  All of that can help us answer your questions faster. You can contact a Seagate Drive Presales representative by telephone at (877) 271-3285 or by email.