Games of Daze/Infomagic - Games of Daze (Summer 1995) (Disc 1 of 2).iso/x2ftp/msdos/qualitas/ramexam.ad

Text File | 1994-02-28 | 15KB | 309 lines

                         RAMEXAM PRESS RELEASE
                         =====================


AVOID BEING BITTEN BY A BAD BYTE
Few components in your PC are as crucial to its operation as memory and
the hardware that manages memory.  Defective memory can cause data loss,
prevent your monitor from displaying properly or even cause your hard
disk to crash.  Every element in your system depends on RAM (random
access memory).  Unfortunately, RAM fails and when it does, lost work is
an inevitable result.

In the case of RAM failure, prevention is the only medicine.  This
document was created to help you understand the role that RAM plays, why
it fails and how to take the steps necessary to prevent the loss of work
that usually accompanies a RAM failure.

WHAT IS MEMORY?
The words "computer memory" are ambiguous.  They are often used to
describe fixed and floppy disk storage, system and adapter "read only
memory" (ROM), video adapter "random access memory" (RAM) and so on.
For the purpose of this document, the term "computer memory" (or just
"memory") refers to the row or rows of system RAM chips that exist
somewhere in your PC.  This is the memory in which your software runs.

The capacity of PC memory to store information is measured in bytes.  A
typical PC today comes standard with several megabytes of RAM.  A
megabyte equals one million bytes (actually 1,048,576) - approximately
the amount of memory needed to hold the text for a 600 page paperback
novel.  Each byte on an IBM compatible system contains eight bits.  This
means that the average PC with four megabytes of RAM has over 33 million
bits -- each one ready and waiting for your valuable information.

Let's take a look at just one bit of memory.  Each bit "holds" one of
two values -- 0 or 1 -- depending on its electrical state.  All the
information in your PC amounts to nothing more than a series of bits.
For example, the word "memory" has six characters, each represented as a
byte in memory, for a total of 48 bits of information:

    01101101 01100101 01101101 01101111 01110010 01111001
    m        e        m        o        r        y

Each bit is significant.  What would happen if the last bit was stored
in a defective memory chip and was stuck as zero?  The new word would be
"memorx".  And if your software program got loaded into the defective
bit then there is a very good chance your system would crash.  Your PC
operates on the assumption that each bit (all 33 million in the above
example) functions perfectly every time you use your PC.

WHY MEMORY FAILS
People expect most machines to break eventually.  We look at all the
moving parts -- think about hard drives spinning rapidly for hours on
end, car engines running for thousands of miles -- and we know that
eventually the machine will stop working.  We see it happen every day.

Why, then, should we be so surprised to learn that system memory fails
also?  RAM itself may not spin, chug or move, but it is acted upon in
countless ways -- ways that, given RAM's fragile nature, can have
devastating effects.

In addition to faulty RAM, errors may occur due to faults in the memory
subsystem - the hardware that manages the RAM.  Unfortunately, there is
no way for software to determine the difference between defective RAM
and a defective memory subsystem.  The causes for failure, though, are
the same.

Here are some of the most common (though by no means all) causes of
system memory failure:

Static Electricity
If you have opened your personal computer then you know that under the
metal case are relatively vulnerable electronics.  Brushing against
system RAM while carrying even the slightest static charge can destroy a
chip by subjecting the it to momentary discharges of excessive
electricity.

Power Surges (large and small)
We all know about the devastating effect lightning can have on a PC.
While a $20 surge protector may reduce risk, it does not eliminate it.
In fact, power brown-outs -- where power levels dip momentarily (because
somebody upstairs just started their blow dryer) -- are not handled by
most surge protectors and can be just as damaging over time as surges.
Actually, your PC is hit with a power surge every time it is turned on
and electricity rushes into the cold system.  Even when these brown-outs
and surges do not cause immediate problems, they stress the
semiconductor chips, which has a cumulative damaging effect.

Dust, Smoke and Pet Hair
Did you ever wonder why the television is usually the dustiest spot in
the house?  Dust and other air impurities are attracted by the
electrical charge inside appliances like your TV and PC where they
settle.  Over time, these materials can build up enough to carry
electrical charges and "short" the PC's circuitry.  The dust also forms
a blanket, diminishing the electronics' ability to release heat and stay
cool.  This results in heat stress and additional potential damage.

Changes in Temperature
Put your hand on the back of a PC that has been running for several
hours.  It is very warm.  As with all things, PC components expand when
their temperatures increase.  Components of different materials (like
the metal RAM prongs and the plastic material they are attached to)
expand and contract at different rates.  Listen closely to your PC creak
when turned off after hours of use.  This expansion and contraction can,
over time, stress the system RAM as well as the connections between the
RAM and the other components.

Though we can take precautions, there are no guaranteed methods for
eliminating all chances of memory error.  What we can do, though, is
minimize our chances of losing work because of defective memory by using
RAMexam to test for it regularly.

WHAT IS RAMEXAM?
RAMexam is a sophisticated, yet easy to use, software utility that tests
system RAM and identifies defective memory before it leads to lost work
and data.

While the causes of memory failure are many, the types of RAM failure
are few.  RAMexam operates using the knowledge of these limited (but not
singular) ways that memory fails.  Currently available, general-purpose
diagnostic software always implements less sophisticated algorithms that
can miss errors, including situations where bits are unreliable only
when other bits hold specific values.  Under such circumstances there is
no assurance that memory errors will be detected:

   "Traditional tests include many well-known tests such as GALPAT,
   checkerboard, sliding diagonal, etc.  (Breuer, 1976).  These tests
   were not based on a fault model (such as the stuck-at, coupling or
   pattern sensitive fault models); consequently, their quality, in
   terms of fault coverage, cannot be proved." (1)

Additionally,

   "The RAM test algorithms [of the types implemented in RAMexam] are
   more effective than the traditional tests (such as Zero-One) which
   are still often used.  The new algorithms are superior in terms of
   the required execution time as well as the degree of fault
   coverage...  Zero-One and Checkerboard [tests] have a very
   questionable fault coverage." (2)

RAMexam uses an underlying consistent fault model to detect RAM errors
efficiently even in complex, multiple fault situations.  Using
sophisticated strategies of writing and reading bit patterns in memory
-- where each strategy targets a specific type of failure -- RAMexam
provides faster and more effective testing.

Here is a description of the categories of failures for which RAMexam
tests:

Stuck-At Fault:  One or more bits retains the value that exists in the
memory when the system boots, regardless of attempts to write new values
into the memory.

Transition Fault:  Once changed, the value in the defective bit becomes
stuck-at.

Unlinked Inversion:  A bit changes spontaneously and erroneously as the
result of change to a bit elsewhere in memory.

Linked Inversion:  A bit changes spontaneously and erroneously as the
result of changes to two or more bits elsewhere in memory.

Unlinked Idempotent:  A bit becomes stuck-at as the result of a change
to a bit elsewhere in memory.

Linked Idempotent:  A bit becomes stuck-at as the result of changes to
two or more bits elsewhere in memory.

RAMexam detects singular and multiple (coupled) occurrences of the above
errors.

WAYS TO USE RAMEXAM
RAMexam may be used several ways:

* You can run RAMexam every time you boot your system by including
RAMexam in your AUTOEXEC.BAT.  When running RAMexam this way, you should
use the command line switch for a "Quick" test.  Running RAMexam at
system start-up will add between a few seconds and a few minutes to the
time it takes to boot your system, depending on how much memory you have
and the speed of your system.  RAMexam includes RSetup, a utility that
can configure your system testing automatically.

* You can run RAMexam as often as you like from the DOS prompt.
RAMexam's interactive interface and on-line help make it easy to choose
the appropriate test.

* RAMexam can test only available memory (you wouldn't want a memory
tester to write through existing data in memory).  You can use RAMexam
for more extensive testing by running it on a "clean" system without
resident software such as disk caches, RAM disks and memory managers
active.  Running RAMexam with no other software active is the most
effective way to test your system.  The MAKEBOOT program, which is
included with RAMexam, will create a bootable diskette for this purpose.
This provides an easy way to test your system memory fully.

A WORD ABOUT WINDOWS & MEMORY TESTING
When Microsoft Windows starts up one of the first things it does is to
grab almost every available byte of system memory.  Conventional memory,
high DOS memory (UMBs) and extended memory are all allocated.

Windows users should be especially zealous about doing periodic RAM
testing because Windows is one of the few applications to use the
multiple megabytes of RAM on most systems.  Frequently, a system will
run without incident until Windows loads -- at which point Windows
accesses a byte of defective RAM that previously had not been used.  RAM
testing is an effective pre-treatment because it allows you to find the
defective RAM before Windows trips on it.

MS-DOS 6.2 MEMORY TESTING
Microsoft recently acknowledged the need to test system memory
regularly.  The extended memory provider (HIMEM.SYS) that is included in
MS-DOS 6.2 and later includes a basic memory test.  Unfortunately, DOS's
memory test has the following limitations:

*       It performs only a single, basic test that can only detect the
simplest errors, which are likely to be found earlier by the system's
power-on-self-test
*       It tests only extended memory, not conventional memory.
*       It includes no scheduling capability.
*       The only way to invoke the test is to reboot the system.

The inclusion of the test within the operating system, though, supports
the premise that RAM does fail and the only way to avoid lost work is to
take preventive steps, including RAM testing.

A NOTE FOR OS/2 USERS
RAMexam can test the memory on systems that run OS/2 -- in fact RAMexam
will test RAM on any Intel 386, 486 or Pentium compatible microprocessor
regardless of the operating system.  The user will need access to a
system running DOS so that they can first install RAMexam on that system
and use MAKEBOOT.COM to create a bootable test diskette.  (MAKEBOOT will
not run in an OS/2 DOS session because OS/2 does not support the
necessary DOS SYS.COM command.) Once created, the diskette can be used
to test any Intel 386 compatible or above based system.

HOW TO AVOID MEMORY ERRORS
As with most of life, a byte of prevention is worth a megabyte of cure.
Maintaining a proper environment for your PC can significantly reduce
the chance of memory failure.  Here are some tips:

*       Work in a dust-free environment.
*       Keep pets away from computer work areas.
*       Do not smoke in the same room as your PC.
*       Plug your PC into its own electrical circuit.
*       Use a surge protector or, even better, an uninterruptable power
supply (UPS).
*       If you use a modem or fax board, make sure that you use a
telephone line surge protector.
*       Always use a grounding cable when opening your PC.

Even with these precautions, there is no guarantee that RAM will not
fail.  RAM testing, though, will significantly reduce the risk of losing
work to defective RAM.

CONCLUSION
Trusting your documents to a personal computer can be risky.  Hard disks
crash, viruses strike and RAM fails.  The risk of suffering serious
setbacks, though, can be substantially reduced by taking easy
precautions.  Just as you would back-up your hard disk and run an
anti-virus utility, you should periodically test your system RAM.

When you use RAMexam, you benefit from the years of memory management
experience that only Qualitas, the makers of 386MAX and BlueMAX, can
bring.  RAMexam is unique in that it is the only dedicated RAM testing
utility available.  Unlike system diagnostic utilities that are designed
to identify problems after you experience symptoms, RAMexam is designed
to detect problems before you suffer their consequences.

Founded in 1983, Qualitas, Inc.  is a leading developer of
high-performance system utility software.  With a commitment to
cutting-edge technical development, Qualitas has built a reputation for
quality, performance and value.  For additional information, contact:
Qualitas, Inc., 7101 Wisconsin Avenue, Bethesda, Maryland 20814,
301-907-6700 or at 800-733-1377.

RAMexam will be released very shortly at a $29.95* retail price (plus
$5.00 for shipping and handling).  It can be ordered now from Customer
Service at 301-907-6700.

* The price had previously been quoted here as $19.95.  That was a
misprint.


========================================================================

Footnotes:

1 van de Goor, A.J.  Testing Semiconductor Memories: Theory and
        Practice, pp. 7-8.
2 van de Goor, A.J.  Testing Semiconductor Memories: Theory and
        Practice, p. 164.


Additional Reading:

Abadir, Magdy S.  and Reghbati, Hassan K.  Sept.  1983.  "Functional
Testing of Semiconductor Random Access Memories", ACM Computing Surveys,
pp.  175-198.

van de Goor, A.J.  March, 1990.  "An Overview of Deterministic
Functional RAM Chip Testing", ACM Computing Surveys, pp.  5-33.

van de Goor, A.J.  1991.  Testing Semiconductor Memories:  Theory and
Practice.  John Wiley & Sons, West Sussex, England


November 1993
Qualitas, Inc.