Odd RAM Issue (OT)

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GTS

I have serviced two computers recently with an unusual issue. Both had been
working fine with 2 RAM modules in dual channel mode for several years. A
problem developed out of the blue with no hardware changes whereby the RAM
pair would no longer work compatibly together though either RAM module was
fine by itself.

One of the two (which was crashing constantly with a 0x0000009C:
MACHINE_CHECK_EXCEPTION) had 4 RAM slots, so I was able to try the same two
modules in single channel mode which worked fine. (Memtest 86 identified no
problem in either configuration.)

Note, both of these were a confirmed hardware issue since the same problem
occurred with bootable OS's. Tweaking BIOS RAM settings, trying a different
PSU, etc. was of no help. It seems as if something must have changed
slightly affecting timing or other functionality of one module in the pair.

I'm curious whether anyone else has run into this i.e. a dual channel pair
that would no longer work together.
 
GTS said:
I have serviced two computers recently with an unusual issue. Both had
been working fine with 2 RAM modules in dual channel mode for several
years. A problem developed out of the blue with no hardware changes
whereby the RAM pair would no longer work compatibly together though
either RAM module was fine by itself.

One of the two (which was crashing constantly with a 0x0000009C:
MACHINE_CHECK_EXCEPTION) had 4 RAM slots, so I was able to try the same
two modules in single channel mode which worked fine. (Memtest 86
identified no problem in either configuration.)

Note, both of these were a confirmed hardware issue since the same
problem occurred with bootable OS's. Tweaking BIOS RAM settings, trying
a different PSU, etc. was of no help. It seems as if something must
have changed slightly affecting timing or other functionality of one
module in the pair.

I'm curious whether anyone else has run into this i.e. a dual channel
pair that would no longer work together.
Click to expand...
Is the problem only occurring in Memtest86? I spent weeks trying to get
2 new memory modules to pass Memtest and no matter what modules, I tried
several brands, they always crashed at the same spot. I then tried
Memtest86+ and the memory passed. Maybe the version of Memtest86 I was
trying was too old to support newer chipsets.
 
GTS said:
I have serviced two computers recently with an unusual issue. Both had
been working fine with 2 RAM modules in dual channel mode for several
years. A problem developed out of the blue with no hardware changes
whereby the RAM pair would no longer work compatibly together though either
RAM module was fine by itself.

One of the two (which was crashing constantly with a 0x0000009C:
MACHINE_CHECK_EXCEPTION) had 4 RAM slots, so I was able to try the same
two modules in single channel mode which worked fine. (Memtest 86
identified no problem in either configuration.)

Note, both of these were a confirmed hardware issue since the same problem
occurred with bootable OS's. Tweaking BIOS RAM settings, trying a
different PSU, etc. was of no help. It seems as if something must have
changed slightly affecting timing or other functionality of one module in
the pair.

I'm curious whether anyone else has run into this i.e. a dual channel pair
that would no longer work together.
Click to expand...


yep

I've seen memtest find no errors
but trying different ram solved the problem
 
Michael W. Ryder said:
Is the problem only occurring in Memtest86? I spent weeks trying to get 2
new memory modules to pass Memtest and no matter what modules, I tried
several brands, they always crashed at the same spot. I then tried
Memtest86+ and the memory passed. Maybe the version of Memtest86 I was
trying was too old to support newer chipsets.
Click to expand...

Probably so. Note you misread my post. Memtest (I was acutally using
Memtest86+) did not report any problems.
 
philo said:
yep

I've seen memtest find no errors
but trying different ram solved the problem
Click to expand...
Thanks. I've seen that too, but I'm less interested in the merits of
memtest than the fact that a pair of RAM modules which had run compatibly
for several years in dual channel mode would now only work as single
channel.
 
It certainly can happen as the components on the RAM module age over time,
use, and heat soak.
Playing with memory timing (possible on some MBDs) might allow them to work
together again.
The difficulty comes when you try to decide which module and what part on
the module is at fault.
Cleaning the module pins and the MBD memory sockets with "Golden Grain"
might also help.
(Seems the gold plating or other contact surface treatment can allow stuff
to "grow" if the metal to metal contact is not air tight.)
This can cause the waveforms to get distorted, and thus the memory to fail,
or not operate just as it should.

This almost sounds like a wierd problem I had 40 years ago with a pair of
magnetically regulated 125 Vdc power supplies.
(Swapped the magnetic unit (a special type of transformer) between the two
and they both worked. Swapped them back, and they would not work.
Swapped again, and put them back in service. I never figured out why they
didn't work. The design was old but known to be reliable.
 
Thanks. I also think there must have been some change in some
characteristic in one of the modules. I did try cleaning and also tweaking
RAM timing and voltage on one of the two machines where I saw this without
success. The other didn't have those options in the BIOS.
The weirdest thing is running into this twice over a few months.
Interesting story about the transformers. I think this will remain a
mystery also.
--
 
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