The main question: Why does CPU-Z report the pairs of two 2GB modules as in dual mode and the two 1GB modules as in single mode? Second, which DIMM slots are which channel to put which modules in for dual memory mode. I don 't think this is how Intel 'FLEX' memory controller technology is supposed to work from what I have read. FLEX allows two different sizes of modules to run on a machine but they are supposed to be either dual or in single mode depending on configuration of what slots they are occupying. These are the original modules as this system came with 6GB or RAM. They are identical in voltage, timing, latency and brand with the exception of the size being 2-2GB and 2-1GB modules.

Below is an illustration of is the original memory configuration. This looks like the only purpose would be to attempt to insert 3GB on each channel in belief that the different color black and blue DIMMS delineate channel separation. This machine was abandoned and given away due to a boot issue. My friend, the original owner, had taken it to a repair shop. So, I don't know if they removed the memory and reconfigured it this way or if it was original like this from the Acer factory. Just trying to figure out what memory configuration is correct

The original memory Configuration as of when I received this machine Original Memory Configuration

CPU_Z Memory - Dual mode with like capacity modules grouped side by side split on both colors:

New Current Configuration

CPU_Z SPD - Dual mode with like capacity modules grouped side by side split on both colors:

Original Config SPD Tab Slot 1 and 2 Original Config SPD Tab Slot 3 and 4

Below is the memory configuration that I ended up switching to and I will explain why later. I ended up with this after testing every possible config. Two of the same size pair in the same colored slot, and then one in black and one in blue. One of each size pairs in the same colored slot, and then one in black and one in blue.

Current Memory Configuration Current Memory Configuration

CPU_Z Memory - Dual mode with on the same color:

Original Configuration

CPU_Z SPD - Dual mode with on the same color:

Current Config SPD Tab Slot 1 and 2 Current Config SPD Tab Slot 4 and 4

My research on the web came up with no real standard on memory slot/socket color codes but most info suggest that a brand specific and discretionary. What does not make sense is that no matter where the memory modules are inserted, the 2GB mods always show in CPU-Z as dual channel mode and the 1GB modules always show running in single channel mode (UPDAT with the exception of putting 1 pair of modules both in the first group or the second group of DIMMs) as seen in the CPU-Z images. You will notice how they, along with the ones above, illustrate my point. This means or shows that when a 2GB and 1GB are inserted on the same channel, CPU-Z is reporting that channel to be running in dual and single mode simultaneously. I believe this to be impossible as I don't know any technology that allows a single memory channel to run both dual and single mode at the same time simultaneously. I am assuming something else is wrong. Perhaps CPU-Z not reporting correctly.

Below is a chart showing the test where I ran CPU-Z on both the original config and the current one I ended on, highlighting CPU-Z confusion of reporting impossibilities. I am not completely sure which two slot/sockets are channel one and which are channel two as there is no documentation to be found for this G43 MB but I am assuming the current configuration I have it on now is correct for dual channel mode.

enter image description here

The reason I believe the current config change to be correct and the previous one to be wrong is simply, the system booted much faster. With the original module configuration that put the same pair on separate colors made, the boot time not only increased but the boot screen and the account log-in screen after the system went into user mode would flash. Meaning it would go blank and reappear two or three times. Sometimes the account user name would appear first, followed by a blue background for a couple seconds before the default intended background would load. Also for two days the system seams more stable without the previous boot issue mentioned next. Also, it hadn't frozen up like it did with the old memory config, after going to bed without it going to sleep like it typically does. Course it needed updates and that could have been an MS update freezing while trying to download however many 100's of MB's on my depleated hotspot through my T-Mobile data service at .225Mb/s

  • 2
    Can you show where you are seeing the memory operating in different modes? For information dual rank memory is different from it operating in dual channel mode. The "memory" tab should show what mode your memory is running, while the spd tab shows the type of dimm.
    – Mokubai
    Mar 15, 2019 at 6:51
  • Sure I can. I'll post screenshots in a few. I already have them. Just may have to crop them. Mar 15, 2019 at 6:59
  • You did research on what the colors could mean instead of picking up your motherboard manual and just checking what they state in it? You have a quite a few questions that cover a lot of different things. As for the RAM @Mokubai is right. Your current screenshots from CPU-Z show the rank of the modules which is not the mode. The rank of memory has to do with it's structure and it's not uncommon that small modules would be single rank while bigger modules would be dual.
    – Seth
    Mar 15, 2019 at 7:23
  • WOW, thanks to both of you since I now recall reading about RANK and CPU-Z some 3-4 years ago. Totally forgot about it. Well, I just checked the memory tab and in BOTH the original configuration and the one where the config is now, with like modules in the same color and they both say Dual. That doesn't make any sense because like I stated above, one of those configs is going to have 4GB on one channel and 2GB on another I would imagine. Unless that is what FLEX does. I haven't found enough documentation about how FLEX works on the G43 chipset. Mar 15, 2019 at 7:49
  • And I can't find any manual for this MB anywhere online. I found a setup guide but that doesn't show memory slots or configs. Since both ways say DUAL, maybe its not supposed to matter but I maintain it seams more stable and boots faster with like capacities on the same color. Mar 15, 2019 at 7:50

1 Answer 1


What I figured out with the help of the respondents is:

First of all it is notable that I was reminded that the word 'Single' and 'Dual' under the SPD tab in CPU-Z does not refer to memory channel mode, but 'Rank'. That was one confusion and misconception in the mix.

Second, I finally found a manual to this specific board and even a Service manual and neither had any reference to DIMM color codes or identification of which ones were which channels. Sometimes there is just no documentation for certain specific manufacturers products or main boards regarding DIMM order or identification.

Both the original memory configuration and the current one showed the DIMMs in both the BIOS and CPU-Z as reporting the memory running in 'Dual' mode. Notice the images below.

Original Memory Configuration with 4GB in channel 'A' and 2GB in channel 'B'

Original Memory Configuration

CPU-Z Memory Tab Showing Dual Channel with 4GB in channel 'A' and 2GB in channel 'B'

CPU-Z Memory Tab Showing Dual Channel

Current Memory Configuration with 3GB in each channel 'A' and 'B'

Current Memory Configuration

CPU-Z memory Tab Showing Dual Channel

CPU-Z memory Tab Showing Dual Channel

I arrived at this conclusion by putting the pair of 2GB memory modules in the first group of DIMMs shown below

Test for DIMM channel Identification

CPU-Z Showing single channel with just the first pair of DIMMs populated

CPU-Z showing single channel with 1 pair of modules in 1 Group of DIMMs

It also appears that neither the BIOS or CPU-Z can properly report the memory channel mode as shown in the image below where 3 modules were inserted populating the first three DIMMs which should show some kind of Dual Hybrid or Intel FLEX mode.

**Just 3 modules populating first three DIMMs **

![![3 Modules populating first 3 DIMMs

CPU-Z Report of 3 Module, 3 DIMM Config Memory Mode

CPU-Z Report of 3 Module, 3 DIMM Config Memory Mode

CPU-Z SPD Tab Slot images

My statement of the reason why I thought the original config to be wrongs and the new current config to be correct, being based on observation al boot speed, smoothless and percieved stability was arroneous and not based on any fact but only assumption. The above test proved that assumption wrong.

Conclusion 1. We figured out which DIMMs are on a single channel on this Acer Aspire M3900 with a G45/G43 main board. They are simply the ones grouped together. The two pairs of DIMMs are separated a quarter to three eighths of an inch. The colors are only to guidance on inserting two pairs or kits of different capacities.

  1. We also learned that when inserting three modules or any configuration that would be Dual Hybrid or Intel Flex Mode that this board does not report it in any definitive fashion and simply calls it 'Dual'.

Perhaps the boot issue and errors were from some instability in the Dual Hybrid FLEX mode and the disk controller being set on 'RAID' with only one installed HDD. Only time will tell and if the boot issue never returns, I will consider the memory configuration to be the culprit.

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