T520 display glitches with 16GB RAM

[FragrantHead]

On the off-chance anyone else has seen this ... I upgraded my T520 (i5-2520M, integrated graphics) to 16GB RAM and started getting weird display glitches every now and again. I am using the laptop on it's own, e.g. the built-in display. Every now and again it's as if the display is momentarily disconnected. It's hard to describe, but the effect is similar to what happens when an external monitor isn't properly synchronised the moment you plug in the cable, e.g. there is interference or half-a-screens worth displayed or other momentary distortions.

There is no instability otherwise. I ran the Windows 7 memory test, memtest86 (for 6 hours) and Prime95 (for 1.5 hours so far). No problems.

The memory is from Crucial. Now I know the T520 isn't rated for 16GB (2x8GB), neither by Lenovo nor by Crucial, but it seems this works for others. Also Crucial approves those exact 8GB SODIMMs for the W520. Same chipset, same CPU generation.

What's your experience with > 8GB of RAM? Is there a genuine reason why Crucial and Lenovo don't officially approve this for the T520 or is it just something with my machine?

[brchan]

Have you tried reseating the LCD cable at both ends? If you installed the RAM into the slots under the keyboard, you might have bumped the LCD cable and made it loose.

[FragrantHead]

(Slaps forehead) Now why didn't I think of that. Thank you!

[FragrantHead]

Well, I've examined the LCD cables. All of them seem very tightly fitted and, frankly, I'm afraid to touch them for fear of making things worse. The biggest one is located closest to the memory, but separated by plastic reinforcement and protected by a metal bar over the top. I'm quite sure I couldn't have accidentally knocked it loose. Thanks for the feedback though. I have re-seated the memory. We'll see how it goes.

[rkawakami]

My recommendation would be to run memtest86+ on the system for a couple of hours. Enough to allow the diagnostic to fully complete at least 3 passes through all of the patterns. Also verify that it recognizes all installed memory (look at the upper left of the display for memory size info).

ref: http://memtest.org/#downiso

[FragrantHead]

I notice there have been over 200 views of this thread. It turned out to be bad memory. I tried the newly-ordered 8GB modules in various combinations with other RAM modules that I have. The problem only occurred with one of them, when used in dual-channel mode with another module. In other words, one of the two was faulty. This only affected the display during my time with it. 6 hours (2.5 passes) of memtest86+, as well as repeated tests with Windows own memory testing tool, Intel's Extreme Tuning Utility and Prime95 all found no errors. The machine was completely stable otherwise.

[rjwilmsi]

Good that you solved the issue, it reminded me of http://support.lenovo.com/en/documents/ht001223 but that affected the 00 series not the 20 series (a friend's X200s had this issue until I turned of VT-d)