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Summary

Faulty system memory is one of the most common sources of system failure. Ultra-X, a small Santa Clara, CA-based company specializing in system analysis tools manufatures a small PCI card containing its own operating system as well as the software to give any system memory a thorough workout. Aside from reporting errors as they occur in real-time, RAM Stress Test Pro also gives the exact location of the errors in an easy to read X-Y plot. Embedded benchmark tools as well as the possibility to change timing parameters on the fly by means of PCI register editing (similar as WPCREDIT) allow to test SDRAM, DDR or VCM modules in the very system that they are supposed to run in. Overall, a very impressive piece of hardware R.S.T. Pro is an extremely useful tool for pinpointing memory errors as opposed to other system failures, albeit at some price. For the professional system builder, R.S.T.Pro should be a very attractive tool, though. .

The two most common sources for misbehavior or failure of PCs are either insufficient or low quality power supplies or bad memory. The first scenario usually happens in upgrade situations where an existing case is re-used to house a new mainboard and CPU with much higher power demand than the original equipment or else, when a cheap case is bought at a bargain price. Often, even brand name cases are going to chop-shops where the power supplies are removed for individual resale and the cases are retrofitted with low cost, low quality components. This can easily be recognized by visual inspection and avoided by sticking with brand names or else units recommended on the CPU manufacturers' websites.

With memory, the situation is somewhat different. Sure, there are situations where simple visual inspection can reveal faulty modules, broken traces, even missing chips or a confetti of different chips on the same module are telltale signs for trouble ahead. For the home user, the recommendation is easy, stick with the mainbrands and don't ever buy anything from a store that does not offer an unconditional life-time warranty with full refund of the purchase price.

For the system integrator, the situation is somewhat different, since larger quantities are involved and sometimes a bargain sounds too good to let it pass. Other possibilities involve recombining and carry-over within existing systems, particularly in the corporate and small business environment where not everybody needs to have the latest and greatest setup. In this environment, there is a high probability for migration of marginal hardware into a system where the particular piece will simply cease to function properly.

One problem related to memory errors is that they are often hard to diagnose. HDD corruption, screen distortions and partial blackouts as well as the occasional BSOD or spontaneous reboots can be caused by faulty DIMMs as well as by anything else in the system. In addition, some errors will only occur under given amount of load. So the question is how to attack these errors and see what they relate to.

The probably most trivial solution is to swap DIMMs with another system and see whether the errors continue. It is a valid approach but not necessarily the most conclusive. Another much better way is to use one of the memory testing programs that use certain patterns to stress the entire memory array and then generate a report about the findings. Several such programs are available either commercially or as free download:

• RAM Stress Test (RST), RST Pro, PHD PCI and QuickTech Pro (commercial products from Ultra-X),
• DocMem (freeware from CST, Inc.)
• BCM Diagnostics (BCM Corp)
• MemTest86 (freeware from Chris Brady).

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