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I think I have bad RAM, please advise


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I installed two Corsair CMX512-2700LLPT DIMMs in a computer that I built 18 months ago, and they have worked fine until now. However, lately I have been getting some application crashes with memory errors, so I decided to run Memtest 86 and see what was going on.


Using Memtest 86 I discovered that there appeared to be a problem. By removing the DIMMs and testing them separately I was able to isolate one that consistently failed the tests. I have not made any recent BIOS changes, so I believe that this is a bad DIMM.


What should I do? Are there further tests I can run, or should I get an RMA and return it?


Thank you,



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here are my RAM timings (from the BIOS)


CAS: 2

tRCD: 2

tRP: 2

tRAS: 5

Command Rate: 1T


Interleaving: 4 Bank (with both DIMMs, though it is currently set to 2 Bank while I am running with only one DIMM)


No overclocking of any kind.


With both DIMMs, they were installed in slots 1 and 3. However, with only one DIMM it needs to be in slot 3 (for stability). The DIMM that failed was the one that was originally in slot 3.


Please let me know if any other info is needed,



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  • Corsair Employees

Please make sure that you have the latest BIOS for your MB and load Setup/Optimized default settings, and try the following BIOS settings;

TwinX1024 or TwinX512-2700LL

CPU Freq: 166MHz (333 FSB) or 200MHz (400 FSB)

System Performance: User Define

Memory Frequency: 100%

Resulting Frequency: 166MHz (333 FSB) or 200MHz (400 FSB)

Memory Timing: User Define

SDRAM CAS Latency: 2T

SDRAM RAS to CAS Delay (tRCD): 3T

SDRAM Row Precharge (tRP): 2T

SDRAM Active to Precharge Delay (tRAS): 5T

DDR Reference Voltage: 2.7 Volts

AGP Voltage: Default *unless you have ATI (9200 or 9600) or NVIDIA (5200 or 5700) then 1.6 Volts suggested!*

All other settings are motherboards defaults

Then please test them one at a time with http://www.memtest.org and let’s make sure it's not some other issue! I would run the test for at least 2-3 passes to be sure!

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I downloaded the latest BIOS, selected "Load Optimized Defaults," and then adjusted my manual settings to agree with your suggestions.


The result: both modules worked perfectly! I let Memtest 86+ run three complete cycles with each DIMM and there were no errors.


What should I do next? There were errors before, otherwise I would not have posted here. The brochure for this RAM says that it is tested at 2-2-2-5 with a command rate of 1T. However, when I click the link in your sig it says that there are tested at 2-3-2-5 and makes no mention of the command rate (do you know what the command rate is?). I also wonder if the problem might occur if I have both of them in at one time. All I'm sure of at this point is that is I set them to 2-3-2-6 with a command rate of 2T, they work correctly individually.


What test do you recommend I run next? Should I try for more aggressive timing? Is it realistic to expect any faster performance from this RAM (especially given that I have been using it for 18 months already)? Or, should I test it all together?



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I decided that you probably would not be able to get back to me tonight, so I went ahead and did some further testing. Here is the format for timing that I am going to use: (CAS - tRCD - tRP - tRAS - Command Rate). Note that I used 4-bank interleaving for all of these tests.


Starting with the module that was giving me errors earlier I tested the following:

(2 - 3 - 2 - 5 - 2): everything works

(2 - 2 - 2 - 5 - 1): errors

(2 - 2 - 2 - 5 - 2): errors

(2 - 3 - 2 - 5 - 1): everything works


Then, I put in the second module (which had passed all test correctly even at (2 - 2 - 2 - 5 -1)) and tested them together:


(2 - 3 - 2 - 5 - 1): everything works


This last setting appears to be all the speed that I can get, and I am able to do it with both modules installed at the same time. Are there any further tests that you want me to try?

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