Absolute Beginners Guide to Upgrading and Fixing Your PC
| Before we get into installing hard disk drives, let's take a minute to examine how a hard drive works. As you can see in Figure 4.1, a hard drive consists of multiple rigid-metal platters, stacked on a spindle inside a sealed enclosure. The spindle is attached to a motor that spins the platters at very high speeds. Figure 4.1. The inside of a hard drive looks like this.
Hard disk platters are coated with a special material that enables the storage of information in magnetic patterns. Data is written to and read from the platter by means of an electromagnetic read/write head. Each platter is divided into sectors; each sector contains 512 bytes of data. Understanding Hard Drive Specs
When you go shopping for a new hard drive, you need to understand the relevant specifications in order to make an informed buying decision and get the right hard drive for your system. This information, typically available somewhere on the drive's packaging tells you how much data the disk can hold, and how fast it can access that data. (Faster is better, of course and also more expensive.) Of these specs, you'll want to focus your attention on size, speed, and price. Given the low prices of hard drives today, you'll probably want to spend a few extra bucks to get a larger-capacity drive if your system can handle it. If you're using disk-intensive applications (such as PC games or audio/video editing programs), you'll also want to spring for the faster 7,200 RPM models. And, of course, price is always a factor; make sure you make the price/performance compromise that works best for your specific needs. Capacity
Disk drive size is typically measured in gigabytes (GB). The bigger the drive, the higher the price. caution
Access Time
Access time is the amount of time it takes for the heads to locate a specific piece of data on the hard drive. Manufacturers typically specify the "average access time," because the actual seek time varies depending on the location of the heads and where the next bit of data is stored. Spin Rate
This spec measures the speed at which the platters spin, in revolutions per minute (RPM). Faster-spinning drives result in faster data transfer rates (discussed next); most drives today spin at either 5,400 RPM or 7,200 RPM. The slower speed is acceptable for traditional office use, but you'll want a faster drive if you're doing a lot of audio or video-related tasks. Data Transfer Rate
The data transfer rate is the speed at which the system copies data from the hard drive to your computer (and vice versa). This spec is typically measured in terms of a programmed input/output (PIO) or Ultra Direct Memory Access (UDMA) mode. For example, a drive with a peak transfer rate of 100MBps is labeled UDMA 100 (also known as UDMA mode 5). Make sure the PIO or UDMA mode of your new hard drive matches the specs of your system unit although, in most cases, if you get a faster hard drive than your system can handle, it can be configured to run at a slower mode to ensure compatibility. Drive Interface Type
There are several different interfaces available that control the communication between your hard drive and your PC. The two primary interfaces in use today are
Most hard drives today use some variation of these two interfaces. The IDE/ATA standard, especially, has inspired a raft of progeny, all promising faster performance than the basic IDE interface. These subsets of IDE include UDMA, UIDE, AT-6, Fast ATA, and Ultra ATA. All of these interfaces utilize the basic IDE-type connector, so compatibility generally isn't a huge problem. "Mike Sez"
If you're working with an older PC, you might encounter some additional, now-obsolete interfaces, such as ST-506, ESDI, and MCA-IDE. If your system uses any of these interfaces, it's an antique; junk the thing and buy a new PC! Disk Drive Manufacturers
When you're looking for a new hard disk, it pays to stick to the major manufacturers. Here are some of the companies that specialize in magnetic storage media:
|