Memory testers are specialized test equipment used to test and verify memory modules typically in SIMM or DIMM configurations. It detects functional failures of memory modules.
Types of tester
Memory module testers can be broadly categorized into two types, hardware memory testers and software diagnostic programs that run in a PC environment. Hardware memory testers have more sophisticated and comprehensive test features built into the tester as compared to software diagnostic testing program. Software diagnostic does allow for detection of possible problems when memory modules are already installed on the computer system.
Software testers
Memory diagnostic software programs are low cost or free tools used to check for memory failures on a PC. They are usually in the form of a bootable software distribution on a floppy disk or CD-ROM. The diagnostic tools provide memory test patterns which are able to test memory starting from the base memory to extended memory. The main disadvantage of software diagnostic programs is the inability to perform tests when a PC refuses to boot-up due to memory failure or a faulty motherboard.
Detected faults
Memory testers are designed to detect two types of faults that affect the functional behavior of a system ( memory chip, logic chips or PCB board). They are
- Non-Permanent faults
- Permanent faults
Non-Permanent faults occur at random moments. They affect a system's behavior for an unspecified period of time. The detection and localization of non-permanent faults are extremely difficult with a memory tester. Sometimes non-permanent faults will not affect the system's operation during testing.
There are two types of non-permanent faults :
- Transient fault
- Intermittent fault
Transient faults are hard to detect, and there are no well defined faults to detect. Errors in ram introduced by transient faults are often called software errors, the following examples are possible factors that will contribute to transient faults :
- Cosmic Ray (UV light)
- Alpha Particle (Dust)
- Pollution
- Humidity
- Temperature
- Pressure
- Vibration
- Power Supply fluctuations
- Electromagnetic interference
- Static electrical discharges
- Ground loops
Intermittent faults are caused by non-environmental conditions such as:
- Loose connections
- Deteriorating or aging components
- Critical Timing
- Resistance and capacitance variation
- Physical irregularities
- Noise (noise disturbs signals in the system)
Permanent faults affect the logic values in the system permanently, these faults are easier to detect using a memory tester. Examples include:
- Incorrect connections between integrated circuits, boards….etc (e.g. missing connections or shorts due to solder splashes or design fault)
- Broken component or parts of components
- Incorrect IC Mask, (Manufacturing problem)
- Functional design errors (logical function that had to be implemented, is designed incorrectly.