CertiGuide to A+ (Core Hardware)  9  Chapter 0011:  System Memory

Pop Quiz 0011.00 1 Parity RAM

No matter how good you are at setting up and using a computer, sometime, somehow, you are going to get errors. 90% of the times, errors exist between seat and keyboard, i.e., the user. However, the other 10% is often credited to the operating system or poorly written software. What many computer users don't understand is that many of these errors that are credited to bugs in the software are actually errors that occur in the storage of the data in memory. There are two types of errors that can occur in memory.

The first type of memory error is called a hard memory error or a repeatable error. A hard error is typically generated by a faulty piece of hardware that will consistently return incorrect results. They typically indicate loose memory modules, bad chips, a defective motherboard, or other physical hardware problems. Because these are repeatable errors, they are easy to diagnose and fix.

The second and more common type of memory error is called a soft memory error, or transient error. This type of error occurs when a bit reads back an incorrect value once, and then reads back accurate values after that. Soft memory errors are obviously much more difficult to diagnose and are often credited to the operating system or poorly written software. Soft errors can and will repeat themselves. The time it may take to see that error again can range anywhere from moments to years. These errors are often the result of poor quality hardware, defective components, power sags or surges, and even natural phenomenon such as radioactivity or neutrinos. The best way to combat these errors and to tell them from software bugs, is to use special memory that can detect and report soft memory errors.

Pop Quiz 0011.00 1 Parity RAM