Programming Embedded Systems in C and C++

Memory Testing 63

Common Memory Problems

Before learning about specific test algorithms, you should be familiar with the

types of memory problems that are likely to occur. One common misconception

among software engineers is that most memory problems occur within the chips

themselves. Though a major issue at one time (a few decades ago), problems of

this type are increasingly rare. The manufacturers of memory devices perform a

variety of post-production tests on each batch of chips. If there is a problem with a

particular batch, it is extremely unlikely that one of the bad chips will make its

way into your system.

The one type of memory chip problem you could encounter is a catastrophic fail-

ure. This is usually caused by some sort of physical or electrical damage received

by the chip after manufacture. Catastrophic failures are uncommon and usually

affect large portions of the chip. Because a large area is affected, it is reasonable to

assume that catastrophic failure will be detected by any decent test algorithm.

In my experience, a more common source of memory problems is the circuit

board. Typical circuit board problems are:

• Problems with the wiring between the processor and memory device

• Missing memory chips

• Improperly inserted memory chips

These are the problems that a good memory test algorithm should be able to

detect. Such a test should also be able to detect catastrophic memory failures ...