Dual channel with 2x4 + 2x2 and 3x4\2 DDR3 Test thread

[dasa]

Rather than take the thread off topic where this info popped up I thought I would start a new thread here.
So I had the belief that dual channel would still work but this post through that into doubt.

Flex only works on system where the IMC it's driven by the mobo chipset and not into the CPU.. so, "flex dual channel technology" doesn't work anymore since nehalem on intel. other motherboards have the ability to map two dual channel slots and one single channel slot but at the expense of all modules being limited by the slower and smaller capacity one.. so even if he is lucky to have a mobo that support that feature (which certainly a P67 chipset wont) then the newer 2x8gb kit will run also as 2x4 so he will left with a total of 16gb of RAM with a high chances of crashing, BSOD, and a large etc of issues.

Certain workstation stuff allow for MCU + IMC such as IBM's power8 and power9 CPUs for onchip and offchip eDRAM purposes but again that's not typical.

I decided to check for myself and the more data the better so anyone else that wants to run a few tests jump in.

So first up a older system and I will try test a 3770K Maximus V Gene system later. Unfortunately I only have two sticks of DDR4 for the 6700K.

Core i3-540 HT 3533MHz / Gigabyte H55M-USB3
Both RAM look to be Dual Rank with 16 chips each stick.
Testing with AIDA64 in Windows 10

2x2+4GB Total 7.9GB in windows CPU-Z reports DC Mode Symmetric
CPU CPU Clock Motherboard Chipset Memory CL-RCD-RP-RAS Read Speed
Dual DDR3-1600 8-9-9-24 CR2 12380 MB/s Read
Dual DDR3-1600 8-9-9-24 CR2 11258 MB/s Write
Dual DDR3-1600 8-9-9-24 CR2 16050 MB/s Copy
Dual DDR3-1600 8-9-9-24 CR2 94.5 ns

2x2GB with 2x4GB 11.9GB in windows CPU-Z reports DC Mode Symmetric
Dual DDR3-1600 8-9-9-24 CR2 12389 MB/s Read
Dual DDR3-1600 8-9-9-24 CR2 10956 MB/s Write
Dual DDR3-1600 8-9-9-24 CR2 16234 MB/s Copy
Dual DDR3-1600 8-9-9-24 CR2 87.2 ns

2x4GB 7.9GB in windows CPU-Z reports Single Channel
DDR3-1600 SDRAM 8-9-9-24 CR2 10450 MB/s Read
DDR3-1600 SDRAM 8-9-9-24 CR2 11173 MB/s Write
DDR3-1600 SDRAM 8-9-9-24 CR2 10715 MB/s Copy
DDR3-1600 SDRAM 8-9-9-24 CR2 96.5 ns

2x4GB 7.9GB in windows CPU-Z reports DC Mode Symmetric
Dual DDR3-1600 8-9-9-24 CR2 12277 MB/s Read
Dual DDR3-1600 8-9-9-24 CR2 11150 MB/s Write
Dual DDR3-1600 8-9-9-24 CR2 17116 MB/s Copy
Dual DDR3-1600 8-9-9-24 CR2 94.4 ns

2x2GB 3.9GB in windows CPU-Z reports DC Mode Symmetric
Dual DDR3-1600 8-9-9-24 CR2 12332 MB/s
Dual DDR3-1600 8-9-9-24 CR2 11151 MB/s
Dual DDR3-1600 8-9-9-24 CR2 17341 MB/s
Dual DDR3-1600 8-9-9-24 CR2 92.7 ns

So other than copy dual channel doesn't seem to make much difference with this system and 4 sticks seems to drop latency a bit but since sub timings were left on Auto maybe this affected the results a bit.

Edit:
On further testing it seems that with three sticks the performance varies depending on where the data lands.
I was getting a bunch of runs then that performed the same as single channel till I opened a bunch of programs that must have filled the single 4GB stick then AIDA64 tests performed more like dual channel.
Hopefully the 3770K system will make this a bit more conclusive.

 

[Araxie]

worth to mention, that chip is clarkdale (32nm die shrink of nehalem) with the memory controller on the mobo.. from sandy bridge onwards the memory controller it's integrated into the CPU. which it's why that kind of memory configuration doesn't work anymore.. looking foward the 3770K test.. good job there taking the time to do the testing..