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Re: Memory test?

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On Sat, 26 Dec 2015 16:15:48 -0500, Bill Cunningham <nospam@nspam.invalid> wrote:

>     Is there a memory test you can use to check your memory sticks? I
> have two DIMMs. An AMD 3500+ 64 bit processor. I have linux and can
> use nasm or debug with a DOS6.21 on a virtual machine. Anyone know if
> your computer going on and off could be simply bad RAM sticks or bad
> code somewhere. I don't know RAM addresses.

Some PCs have an advanced BIOS with a built-in machine tester, e.g.,
Dell PC's have a full suite of hardware tests including probably
dozen different memory tests.

Otherwise, you'll probably have to download a bootable CD-ROM image
and burn it.  E.g., Passmark's Memtest86 for Windows.  You could
check out Pyropus memtester for Linux.  Apparently, you can activate
a memory test in the kernel for some Linuxes:

http://raid6.com.au/~onlyjob/posts/MEMTEST_explained/

Depending on the Linux version, you may or may not have full access
to memory.  See mmap() manpage.  You could code a small C program
for DOS. 16-bit app would be limited to low 1MB.  32-bit DPMI app
could test up to 4GB.  You'd need 64-bit mode code to test more
memory than that with DOS.

You might consider dropping a post to comp.os.msdos.* groups, like
comp.os.msdos.misc or comp.os.msdos.programmer to see if anyone
recalls such an app via the old DOS archives.  If they do recall,
and they can't find it, I might be able to.


First, if you're over-clocking, turn that off, i.e., reset the BIOS
settings.  You might be over-clocking without realizing it, e.g.,
if you set any bus or memory or microprocessor speeds manually.
See if the system is stable without it.  If so, the over-clocking
is the problem, i.e., probably insufficient cooling.

Laptops can have overheat problems too because they're so enclosed.

Also, many recent motherboard designs put the memory chips adjacent to
the microprocessor for faster bus speeds.  Unfortunately, they sometimes
direct half the exhaust path for the processor's heatsink directly
onto the memory cards, instead of perpendicular to the memory cards.
So, you have hot air and dusty air blowing onto your memory chips ...
This causes the fine dust, like that which sticks on PC's fan blades,
to accumulate on the memory cards, which can cause memory errors.
I'm having to clean the memory chips in this PC every six months ...
Normality is never having to clean the memory chips.

So, if you're mostly convinced it's a memory error, the very first thing
I'd do is ground myself to not have any static charge, then power down
the PC, turn off the master power switch too, then pop out your memory
cards, and thoroughly blow all the dust off of them.  You might want to
do this over the bathtub.  DO NOT  do anything to cause static electricity
to build up, i.e., no brushes or cloths.  It's acceptable, but ill-advised
for home use, to run them under water.  If you do this, you *MUST* make
sure they're thoroughly dry *BEFORE* applying power.  I.e., use a
compressed air tank or pressurized air can to blow them dry.  You can
generally blow the dust off with your mouth, but you *CANNOT* do so with
the water.  It "hides" under chips, etc, and can't be removed without high
pressure air or heat.  Heating electronics with a hair dryer/heat gun is
acceptable too.  Electronics usually go through a reflow oven or infrared
surface mount oven to solder them around 400 degrees Fahrenheit.  Heat
to solder, wash to remove flux, blow dry with compressed air was once
standard industrial practice.

The next thing I'd do, if the machine is over 5 years old, is to remove
the microprocessor heatsink.  Get some rubbing alcohol, naptha, mineral
spirits etc and remove the heatsink grease from the processor and the
heatsink.  This is messy.  It's not as bad as getting vasoline on your
hands, but still somewhat difficult to remove.  You can try a product
like "Goo Gone" or something with xylene.  Also, have some papertowels
handy.  Avoid touching the grease, if possible.  Put some new heatsink
grease on the heatsink.  Make sure it covers the entire contact area
between it and the processor.  Replace the processor making sure it is
oriented correctly and seated flat/level.  Usually, there are a few pins
that must be oriented to a specific location.  Do not attempt to force
the processor.  Make sure it's in correctly. Most modern machines have
a lever activated pin grid clamping mechanism.  Reattach the heat sink.
Older motherboards were soldered, push in, or simply held by the
processor heatsink.  You can buy the heatsink grease at Radio Shack
(US), electronics supply stores, better quality computer stores, or
mail-order/online electronics distributors.

Finally, check for any flaky or non-functional hardware.  E.g., if
a fan isn't spinning, it's 1) dead 2) needs bearing lubrication
(silicone) or 3) something may be wrong with your power supply, i.e.
intermittent, failing, damaged and unregulated, etc.  If it's a power
supply issue, you may see similar intermittent operation with other
devices, e.g., CD-ROM.  I.e., as the device warms up, power-ups, and
draws more power, the failing power supply goes down.  If a device is
electrically damaged, you can sometimes have the same issue.  If you
determine it is a damaged power supply, the best choice, despite the
loss of value, is to discard everything the machine, after you've
backed up as much data as possible.  If the hardware was damaged,
it can damage a new machine.

If it's a failing video card, e.g., too hot and BGA chip unsoldered,
you'll usually see scrambled video or color "snowflakes" etc.
Sometimes these can be salvaged by reheating the chips, e.g., heat
gun, hair dryer, home oven, industrial reflow, etc.  This likely means
your case interior isn't being cooled properly.  Modern vertical PC
cases generally have two or three fans.  A fan in the power supply.
A fan on the processor heatsink.  Sometimes a fan in front.  You
should also have a fan on the processor heatsink and a fan on
any high-performance video card.  Of course, this doesn't apply to
laptops.  If you're over-clocking, you'll probably need a substantial
heat sink (water) on the processor, and cooling on chips that weren't
heat sinked by the manufacturer, e.g., video, north/south-bridge, etc.


Rod Pemberton


-- 
The idea that sentient beings can be suppressed by a few simple
rules is a farce.  Even so, Isaac Asimov posited such rules for
sentient artificial intelligence.

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Thread

Memory test? "Bill Cunningham" <nospam@nspam.invalid> - 2015-12-26 16:15 -0500
  Re: Memory test? Wildman <best_lay@yahoo.com> - 2015-12-26 22:54 -0600
  Re: Memory test? "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-12-27 01:00 -0500
    Re: Memory test? "Bill Cunningham" <nospam@nspam.invalid> - 2015-12-27 18:26 -0500
      Re: Memory test? "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-12-27 20:52 -0500
      Re: Memory test? Johann Klammer <klammerj@NOSPAM.a1.net> - 2015-12-29 06:19 +0100
  Re: Memory test? "wolfgang kern" <nowhere@never.at> - 2015-12-29 09:42 +0100
  Re: Memory test? "s_dubrovich@yahoo.com" <s_dubrovich@yahoo.com> - 2015-12-31 07:52 -0800

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