I have edited this article many times, and because you are probably interested in the problem (To see if it is like yours), and the solution, i have added a few paragraphs with the information you are looking for at the top, and if you are interested in more details, you can read the old texts, speculations, and the like.

The problem is that, when memory modules are installed alone, they always pass the memory test, but when together, they sometimes pass, and with the same installed memory, other times fail the test with no apparent reason.

As it turns out, even though the ram has the same model number, CPU-Z unveiled that they had different production dates, and for some very strange reason, every 3 of the 6 DIMMs had similar timings (and production dates)

This article describes my problems with the same brand rams with even the same model number, and a surprising difference in SPD data between ram modules, but in reality, this applies more to different models of ram even when they are not on the same channel (In dual channel or three-channel modes). Even though i recall on older models of intel motherboards they say it does not matter as long as identical sticks are installed for a certain DIMM in every channel, it seems the 5XX and 5X series chipsets want the timings to be the same on all modules.

So, the solution was

1- Boot with the first DIMM (RAM module), start CPU-Z, see the timings in the SPD tab. take a screen shot, and label it 1, also label the ram stick 1, do the same for all other RAM modules and label them 2, 3, 4, etc…

2- Compare the timings of the RAM modules, if they are all the same (on the CPU-Z SPD page), your problem is a different problem.

WARNING: We are about to write data to the SPD area of the RAM stick, DO THIS AT YOUR OWN RISK, AND YES, THERE IS A SIGNIFICANT RISK

3- FIX timings in the RAM SPD: If the problem is that they don’t share the same timings (Like my problem), download SPDTool.exe, and read the SPD data from one of the DIMMs into a file, if you have for example 4 sticks with a certain timing and 2 with the other, i would recommend the using the timings from the 4 on the 2 and not the other way around.

4- Boot with other RAM modules and dump the file onto them, make sure the checksum is correct, if the software warns you that the checksum is incorrect, use the software (SPDTool) to FIX THE CHECKSUM.

NOTE: For some unknown reason i had to fix the checksums (There is such an option in the menu of the software), and for some unknown reason, i had to dump the fixed checksum file back onto the source DIMM as well, but it worked.

Also, from the 6 sticks, 3 had timings exactly like the ones from my Kingston models, so i chose that over the other timing set, as for you, when it comes to memory timings, the lower is better (5-5-5 is better than 8-8-8).

Now, the above is what you need to know, if you need more, i didn’t delete anything from the old text, check it out below.

Initial hardware problem description

Less than a year ago (Aug, 26 2010) , I went and got an I7 processor (i7-930), A (X58A-UD3R) 3 channel memory motherboard (6 sticks), and 6 sticks of 4 GB memory (TwinMOS PC3 10600 4GB DDR3 1333 256*8 16IC CL 9.0 U-DIMM 9DCEBNZB-TATP) to achieve that 24GB of system ram (Yes, i need this much to run my own software, the more ram, the faster it runs).

In any case, things did not go well, the motherboard played fine once every time i shuffled* the 6 sticks around, and got memory errors on any second reboot after the shuffle, Sometimes i change something in the BIOS and things work fine for another single boot, and sometimes, i just let the pc with no electricity (Strange since the CMOS battery is new), and things would work just fine.

NOTE *: Shuffled or sometimes introduced a 2GB stick from another computer to replace one of the 4GB DIMMs.

A pity since the ram looked very nice, with aluminum heat spreaders on both sides, (Although you can see that the spreaders do not make contact with ALL the chips under them, but that is not relevant to the problem it appears), and painted in 2 colors, 3 black sticks read Piano Black, and the other blue 3 read Ocean Blue.

So, i am thinking to myself, there is something special about the first boot that makes everything work fine most times after a shuffle, and something is saved for the second boot that gets things messed up, cached SPD ? i don’t know yet, we will work around this together.

In any case, The TwinMOS DIMMs i have cost me $141 * 6= $846, worked fine if you run any 2 DIMMs together (LATER: Appears the 2 DIMMs needed to be the same color and SPD but i didn’t know that) , threw errors on the Gigabyte mobo if all 6 were present.

Got the Kingston for the Gigabyte – All ok

Some time later (March 2011), i got annoyed from the shuffle before you boot game, and decided to get it over and done with, so I downloaded the compatible memory sheet, and sure enough my TwinMos ram was not on that list (LATER: Turned out to be irrelevant), I decided not to waste time on it, and went and got 6 Kingston DIMMs ( KVR1333D3N9/4G 4GB PC3 – 10600 CL9 240-Pin DIMM 9905471-006.A00LF ) at ($59 * 6 = $354) that worked like a dream on the Gigabyte motherboard (No errors at all). even though this exact kingston model was not on the compatible memory sheet.

New Motherboards Intel DH55HC, MSI G41M-P26, and Asrock G41C-S

So now i had 6 TwinMOS DIMMs, and 2 Kingston 2 GB DIMMs (KVR1333D3N9/2G 2GB PC3 10600 CL9 240 Pin DIMM 9905458-009.A00F) not in use, and for a reason i don’t remember (Even though this a few days ago), rather than selling the DIMMs on Ebay or something (Since they all work just fine if used in pairs of 2), i went and got 3 motherboards.

Two of the 3 motherboards had the G41 chipset that can take 2 DIMMs each, and one INTEL DH55HC motherboard that can take 4 DIMMs, thinking that this motherboard (The H55) would run my Ram just fine.

So i updated the BIOS to the latest on all nice new motherboards.

Both G41 motherboards would take any 2 sticks of ram with no problems at all, But the H55 motherboard is doing the same exact thing our Gigabyte motherboard was playing.

On the intel website, it reads that my DH55HC motherboard can take

• 16 GB maximum total system memory (with 2 Gb memory technology)

What is 2Gb (Notice, Bit not byte) technology, and also note that it is taking my 16GBs of twinmos RAM, but not happily.

The timings of the TwinMOS RAM (That our Motherboard allows us to change) are

Multiplier = 10 / 9-9-9-24 / 1.5Volt (Provided by the SPD from the RAM)

But wait a minute, the timings on the black sticks is not the same as the timing on the blue ones !

As it turned out, SPD is stored on Electrically Erasable Programmable Read-Only Memory (EEPROM), and i can rewrite that with some software.

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