Some BIOS setup programs have settings for memory. Normally, most of these settings are to be left alone. In fact, manuals for Award BIOSs warn the technician never to alter the memory settings on the Chipset Features Setup page unless data is being lost. Data loss from memory is extraordinarily rare, so we also recommend leaving these settings alone unless directed to change them by support technicians from the computer/motherboard manufacturer or the BIOS manufacturer.

One memory setting you can change, as discussed earlier, is whether the memory should be ECC/parity or not. ECC/parity memory is not usually necessary except on file servers. An example of when you might change this setting is if you have some good non-parity memory from an otherwise irreparable computer and a computer that needs new memory of that type and speed, but that computer normally took ECC or parity memory. In the event that its BIOS has such a setting, change it to non-parity/ECC before removing all of the old parity/ECC memory and replacing it with the non-parity/ECC memory from the irreparable computer. Under normal circumstances, however, it is advisable to leave BIOS memory settings at their defaults.

Tip For more information about BIOS settings, see your BIOS manufacturer's Web site, your motherboard/computer manufacturer's Web site, or access tech support at unicore.com.

Overview of Hard Drives (Hard Disk Drives, HDDs)

Hard disk drives are so named because they contain hard magnetic disks inside the housing. They are designed to store large quantities of information, and they don't need to be continuously powered in order to hold that data. The vast majority of PCs used today have at least one hard drive, and in almost all of these, the hard drive is used to store the OS, programs, and data. When a computer boots, depending on BIOS settings, the computer searches for boot files on different disk drives, most commonly the floppy drive first, then the hard drive, and then a CD drive. For regular use on any modern PC, the hard drive is the only one that is big enough to hold the required files. In fact, PCs that don't use hard drives are beyond the scope of this tutorial. Note that laptop hard drives are physically much smaller.

Basic Hard Drive Characteristics

Externally, hard drives have a power connector, a data connector, and jumpers. We discuss jumpers later in this tutorial. The power connector is connected to one of the drive connectors from the power supply, and the data connector is connected to the appropriate drive connector on the motherboard. Internally, hard drives have spinning magnetic platters and heads. Heads are small devices that store and pick up magnetic information from the platters; they have similarities to heads on cassette tape machines. Storage areas on the platters are divided into portions called cylinders, sectors, and clusters. Information about these parameters appears in the hard drive documentation and often on the paper label on the housing. When you go to the BIOS setup page that shows hard drive information, you might see some or all of this information and possibly more. Under the "type" category, there are usually three or more settings: User, None, and Auto (other settings might not apply to stationary hard drives). The None setting disables the drive. User allows the user to input the settings manually. If you choose User, the settings must match those of the drive exactly. Auto has the computer detect the drive information; on the vast majority of newer computers, Auto is the best setting.

Selecting a Hard Drive

There are two main interfaces used today: Enhanced Integrated Drive Electronics (EIDE), and Small Computer System Interface (SCSI, pronounced "scuzzy"). SCSI drives perform better and have features that provide for higher reliability than EIDE drives. Not surprisingly, they are much more expensive than EIDE drives, and thus are used mostly in mission-critical business applications, and rarely in standard PCs. Because of this, SCSI devices are generally beyond the scope of this tutorial, although some of the information in this tutorial applies to SCSI also. There is a new interface, just becoming available as of this writing: Serial ATA (SATA). SATA drives are set to replace EIDE drives, and many new motherboards have connectors for both types.

We divide the factors to consider when selecting a hard drive into two categories: compatibility and quality.

Compatibility

The following factors must be considered to make sure a hard drive will work in a given system:

Form factor: Hard drive form factors aren't the same as other form factors. They have to do only with fitting the drive in the case, and thus are applicable only with internal hard drives. Desktop and tower computers are standardized for the 3.5-inch form factor, although it is possible to use smaller drives in one of these computers. (We discuss installing a small hard drive in a full-sized system later in this tutorial). Laptops take 2.5-inch drives or smaller; check with the laptop documentation or Web site, or remove the drive and look at the label.

Ultra Direct Memory Access (UDMA) speed rating: This refers to the speed of data transfer between system memory and the hard drive buffer measured in megabytes per second and, at the time of this writing, has possible values of 33, 66, 100, and 133. Check the motherboard's maximum transfer speed and select the fastest hard drive the user can afford. Motherboards can accept any drives rated at their maximum speed or slower.

EIDE or SATA: As of this writing, some new motherboards have connectors for both, but older boards accept EIDE only. SATA expansion cards for PCI slots are available.

Quality

Any time you are purchasing a hard drive that is to be the main or only hard drive in a computer, you should take the following quality indicators into account. A cheap hard drive will provide poor performance in most cases, but might be well suited for file archiving when the files aren't accessed often.

Here are factors to consider when attempting to purchase the highest quality hard drive for the money:

Warranty: Previously, many hard drives came with a three-year manufacturer's warranty. More recently, one-year warranties have become most common. Try to get three years if possible.

Buffer (cache memory): This is high-speed memory that is used to store a small amount of data while it is waiting to be read from or written to the drive. As this significantly improves performance of the computer, the bigger the buffer, the better. 2MB is good; 8MB is much better, especially when the user works with graphics-intensive programs such as video editing or games, or other high-stress programs. Drives with less than 2MB of cache will likely provide poor performance.

Platter speed: The most common speeds are 5400 and 7200 revolutions per minute (RPM). The faster the platter spins, the faster data can be accessed and transferred.

EIDE or SATA: EIDE drives are the ones that PCs have been using for many years now. SATAs are just being introduced as this is written. SATA drives perform faster and more accurately than EIDE. An added advantage is that SATA cables are small, making for easier installation and better airflow than the standard ribbon cables used on EIDE devices. The smaller cables also allow for smaller computers.