|RAMCHECK LX Testers
RAMCHECK LX DDR2
RAMCHECK LX Base Tester
200-pin DDR2 SO-DIMM
200-pin DDR SO-DIMM
66-pin DDR Chip
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TEST ACCURACY AND RELIABILITY
- Q. Can the RAMCHECK memory tester guarantee
that the tests performed on memory modules are 100% accurate?
A. Unfortunately, no. No memory tester, including those costing $500,000
and more, can achieve exhaustive tests (that is, 100% accuracy) due to the
virtually unlimited possibilities of data combinations which may be stored
inside a memory device. While we continuously strive to improve RAMCHECK's test
algorithms and design, we cannot guarantee 100% accuracy of the test results.
- Q. Well, if your memory tester (or
any other tester for that matter) cannot guarantee the test results 100%, then
what is the benefit of having it?
A. While it is difficult to assess the overall accuracy of a memory tester,
INNOVENTIONS testers are regarded as fairly accurate in the industry, as is
attested to by the success of our pioneering products over the years. Many of
our customers have been loyally using our memory testers for decades, going
back four generations (Classic RAMCHECK, old
SIMCHECK, SIMCHECK II, and now the
RAMCHECK memory tester).
The problems that are not detected are usually rare. And in many cases, some
errors undetected by our testers are later corrected with new firmware
releases, as we will discuss below.
In the few difficult situations when a technician is faced with a rare
intermittent problem, RAMCHECK memory tester provides much more information
than merely GO/NO GO. The technician can use the detailed speed results and
structure information to compare among suspected modules and find the one that
is most likely to be the culprit.
With so many "mis-marked" and poorly made modules in the market,
RAMCHECK is an indispensable reference tool. An extremely slow module which is
mis-marked at higher speed can be spotted by the memory tester and save you
from later embarrassment.
With the large variety of memory modules to choose from, it is not enough to
know just the size and speed information marked on the module. Often you need
to know the structure information in order to fit the module in a specific
motherboard. Our memory testers provide you with such information.
- Q. What is the difficulty in
performing exhaustive tests of memory devices?
A. In short, the main problem is that each bit of the memory may be shorted to
quite a few adjacent bits, and there are a huge number of such bits in today's
memory devices. Also, every chip die version has a different topography, even
among chips with the same part number from the same manufacturer. For example,
in a typical 32Mx8 chip there are 256 million bits. Testing possible shorts
between each bit to potential other close-by bits requires an astronomical
number of tests, and each takes a short test time. Therefore, all memory test
equipment must use "optimized" short tests that provide speedy tests
at the expense of missing 100% coverage. Please also refer to Application Note
INN-8668-APN5 for further details.
- Q. What is the difference between RAMCHECK
memory tester and the expensive certifying test equipment used by the memory
A. In order to fully certify memory devices, an expensive tester which
includes customized software and a high temperature environment chamber is used
by the memory manufacturers. While even these testers cannot achieve 100%
accuracy, their customized software is optimized to the internal layout of the
tested device in order to detect hard-to-find bit interferences. Such a tester
requires a long process of test program preparation by the software engineer,
and the test itself is fairly long. Since our testers are optimized for low
cost and simple operation, we do not provide true high temperature testing
which is critical to certification, nor do we require you, the customer, to
program the test for specific internal memory chip die. Therefore, RAMCHECK LX
and RAMCHECK cannot be regarded as a certifying test equipment. And yet, our
product success over the last 20+ years testifies to the fact that we have
developed great reference tools with our improved algorithms and advanced
- Q. I have a "mission
critical" application. Can I rely on your testers to certify my memory
modules in such an application?
A. Absolutely not. Our testers are not sold as a certifying equipment.
Certifying memory test equipment, as mentioned above, must include a high
temperature chamber and advanced customized programming to exactly accommodate
the internal topography of each memory chip (see also Application Note
INN-8668-APN5). Such certifying test
equipment costs $500,000 or more and requires qualified field engineers to
operate. Even these equipment manufacturers will not give you a guarantee of
100% fault coverage.
- Q. What is the nature of hard to find
A. In general, hard to find intermittent errors can be divided into the
Temperature related: These are problems that appear only after a few
hours of operation inside a hot computer. Typically, they cause an increase in
the internal leakage of the DRAM cells or cause "cold soldering" to
break contact at high temperature. Our patented Chip Heat test increases the
temperature of the modules under tests but we do not reach the 70 degrees
Celsius that is achievable only with the heat chamber of an expensive
certifying memory tester.
Pattern sensitivity: These problems are caused by a short (or leakage)
between adjacent memory cells and create a memory failure when the cells have
different data values. These problems are discussed in Application Note
Soft errors: These are radiation related errors, which cause a reversal
of data in a DRAM cell when stray radiation (e.g. alpha particles) hit the
cell. These problems have been reduced over the years of memory development but
they are still regarded as the prime cause for unexplained errors. This
radiation can be generated from the regular ambient cosmic radiation and
therefore, can attack memory everywhere.
Voltage spikes: These errors can occur when voltage spikes inside the
computer cause severe noise in the sense amplifiers inside the memory device.
Our testers simulate voltage changes in our Voltage Bounce, Relative Spikes,
and Voltage Cycling tests but you can never simulate all possible spikes.
- Q. What other issues affect the
accuracy and reliability of your memory testers?
A. The RAMCHECK LX and RAMCHECK test programs are fully written in Assembly for
fast performance, and they include about a hundred thousand lines of code.
While we do our best to clean all the bugs prior to firmware release, there is
no escape from such hidden bugs to be found in our code.
The memory market is also huge, with many developers and manufacturers. There
are new module variations introduced daily and our firmware may not support
some new variations.
We are continuously improve the hardware design of our products, and offer our
customers periodic calibration and hardware upgrades for their test
- Q. Can operator's error interfere
with test results?
A. Although we have made the operation of our testers quite simple and
automatic, the testers include advanced setup features to satisfy the most
demanding users. However, some operators may set it up wrong or misinterpret
the results. For example, if one operator sets the tester at a partial test of
16Mx64, another operator may be confused to see a 16Mx72 module tests at
%16Mx64. This operator may not be aware that the "%" prefix indicate
a setup for partial tests...
- Q. How do you improve the accuracy of
A. Our R&D department is constantly at work to improve our test accuracy.
We are developing various algorithms and continue to improve the electronic
design of our products.
We also receive a lot of help from our customers. When they find a module that
does not test properly, they often send it to us for evaluation. Many
additional support features have been added to our products over the years
through such cooperation with our customers. If you find a module that you wish
to send for our evaluation, please contact our Tech Support department.
- Q. The test results, especially in
the Test Log, provides numerous details. How do they relate to your overall
A. Our memory testers are not simply GO/NO GO testers. They provide numerous
results that should be understood by the customer. For example, a customer may
have a module passing our testers but the test results indicate that the module
is of a special structure. Then the customer is confused to see the module
failing on a certain motherboard. After contacting our Tech Support department
and reviewing the test log, we have found that the RAMCHECK results indicates
that the module will not work on this specific motherboard.
We provide a lot of information on our Web site to allow better understanding
of the test results. And of course, you are always welcome to contact our
Technical Support for more information.
have additional questions, please feel free to e-mail us at
Please remember to include your phone and fax numbers.