- 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
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
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
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
- Q. I have a
"mission critical" application. Can I rely on your
testers to certify my memory modules in such an
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
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 intermittent errors?
A. In general, hard to find intermittent errors can be
divided into the following groups:
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 INN-8668-APN5.
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
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
We are continuously improve the hardware design of our
products, and offer our customers periodic calibration
and hardware upgrades for their test equipment.
- 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 your tests?
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
- 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
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.
If you have additional
questions, please feel free to e-mail us at firstname.lastname@example.org.
Please remember to include your phone and fax