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Dual channel not working

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July 29, 2011 12:31:00 AM

Hello All,

This has probably been asked before but......

I can't get my memory to run in dual channel mode. I have 2 sticks of PNY PC2-6400 in slot 3 & 4 and 2 sticks of Samsung PC2-5300 in slot 1 & 2. There is no setting in the BIOS to change it to dual channel mode. Found the owners manual for my mobo and I'm pretty sure I have the matching pairs in the correct dimm slots. I had different speed dimms running in dual channel on my old computer but just can't get it to work on this one.

Mobo is ORY206 (came out of a dell inspiron 531S).

Do I need to have all of the dimms at the same speed for it to work on this mobo?

Any help would be appreciated.

Daniel
Novice PC guy

More about : dual channel working

a b } Memory
July 29, 2011 1:00:01 AM

ddr2 is backwards compatible, so u should be able to run that memory in dual-channel mode, but dell motherboards have a limited bios, so ud have to look into it,
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a b } Memory
July 29, 2011 1:35:06 AM

Mixing RAM almost always ends up with less than favorable results. Still, to achieve Dual Channel mode, the following conditions must be met:

Matched DIMM configuration in each channel:
1. Same Density (128MB, 256MB, 512MB, etc.)
2. Matched in both Channel A and Channel B memory channels

OR

Populate symmetrical memory slots (Slot 0 or Slot 1)
Configurations that do not match the above conditions will revert to Single Channel mode.

The following conditions do not need to be met:
Same brand
Same timing specifications
Same DDR speed
Memory channel speed is determined by the slowest DIMM module populated in the system.

*This really depends on your motherboard. Some manufacturers use a color
-coded system (meaning use the same colors) and some require that you use the symmetrical approach (meaning same slot on both channels).

Since you're mixing RAM, try this configuration with just one pair:

[CPU] | _ | _ <- If this enables DC mode with one pair, simply use the empty slots for your other pair*

[CPU] | | _ _ <- If this enables DC mode with one pair, simply use the empty slots for your other pair*

*note: Manually configure your BIOS to the settings of the lower quality pair
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July 29, 2011 2:05:47 AM

Thank you for the quick replies.


I've tried both the configurations: [CPU] | _ | _ and [CPU] | | _ _ as well as [CPU] _ _ | | (Dell owners guide says the dimm slot farthest from the cpu is dimm_2) but still haven't had any luck. The slots are color coded as well. When I go to the memory section of the bios everything is greyed out. Dual channel mode does work when I use only 2 sticks of ram in the [CPU] | | _ _ configuration.

Can it be that the mobo doesn't allow dual channel with more than 2 sticks of ram?
Should I put the faster ram in the [CPU] | | _ _ configuration and the slower in the [CPU] _ _ | | config?

I've tried several different configurations but every time I switch them around I have to remove my giant video card first. :fou:  :fou: 

BIOS--- Dell Inc, 1.0.9 01/09/2008 per CPU-Z


Thanks again,
Daniel
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a b } Memory
July 29, 2011 5:15:29 PM

devans said:
Dual channel mode does work when I use only 2 sticks of ram in the [CPU] | | _ _ configuration.


So does DC mode work in the [CPU] | _ | _ or [CPU] _ | _ | configurations?

If it does, then it really doesn't matter where you put the slower RAM. The BIOS will auto adjust to a configuration that accomodates both pairs.
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July 31, 2011 2:48:47 AM

T_T


I tried the PNY (PC2-6400) sticks by themselves in the _ _ | | , | | _ _ , and the | _ | _ configurations and there was no dual channel mode. Stuck the Samsung (PC2-5300) sticks in by themselves in the _ _ | | configuration and dual channel mode worked. So it looks like the PNY ram is the problem, but I had these same sticks + a 1gb + 512mb sticks in my old computer and dual channel mode somehow worked even with the odd pair.

I thought all DDR2 memory was dual channel.
Can you think of any reason it wouldn't work with this mother board?
Is there that much of a difference in performance between dual channel and single channel modes for gaming and some autocad work?


Daniel
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a b } Memory
August 1, 2011 5:47:20 AM

Dual channel configuration is enabled by the motherboard, if the RAM is capable. In essence, both mobo and RAM have to support the technology. That said, there is only one reason that I can think of at the moment, voltage. The old mobo could have had a better voltage regulator, assuming that the old mobo was also in a prebuilt system bought from the store.

As you've found out, a lot of the prebuilt systems don't allow end user's to make too much changes to the BIOS. With the exception of changing boot order; date & time; etc., often times you can't change anything. This also means that the last mobo was better at controlling voltage to the DIMM sockets.

In regards to the PNY RAM, I don't really think that there is anything wrong with it. Still, to answer your question regarding single vs dual channel speed; dual channel is about 5% faster. I really don't think you'll notice a difference in gaming or CAD. Rendering apps, like AutoCAD, require more RAM capacity, rather than speed.
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August 2, 2011 1:35:34 AM

Thanks for the replies T_T


As far as voltage goes, CPU-Z shows all four sticks at 1.8 volts.

1. Is there some kind of Stepping technology that only uses dual channel mode when the system requires it? (tried to test this by stressing the system with 8 youtube videos playing at the same time, while at the same time checking CPU-Z. It never went into dual channel, but it may be because my GPU is doing all of the work.)

2. You say the RAM has to support dual channel, but doesn't all DDR2 run in dual channel if the pairs are matched?

If it is only a 5% difference in performance, cool. But...now it is just a matter of principle. I hate to not have a definitive answer after spending so much time researching it.

3. You think a 4 gig (4 x 1gig) matched kit would work?

4. Have you ever seen a mobo that could accept PC2-6400 but would actually only do dual channel mode at PC2-5300?

5. If one train leaves Austin at 6:00 P.M. at a sped of 60mph and another train leaves San Antonio at 7:00 P.M..........


Daniel
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a b } Memory
August 2, 2011 10:06:19 PM


Daniel,

1. No. It's either you are using dual channel or you're not. You don't turn it on by means of a switch; nor is dual channel contingent upon workload.

2. Not all RAM is made to support the dual channel technology, and certainly not because it is DDR2. The basic gist of dual channel was to alleviate the bottlenecks that occur at the memory controller. Such a bottleneck occurrs when the CPU speed is faster than the RAM speed. DDR2 is the second generation of Double Data Rate RAM. Prior to this, guess what was used. Yep, Single Data Rate.

3. Yes, that would work, and for almost anything you throw at your computer. However, when using all four DIMM slots on a mobo, it is often required to increase the DRAM voltage. For this reason, plus oversized CPU coolers, is why a lot of people elect for a 2 x 2 GB kit.

4. I would have to say no, as I can't think of any mobo that supports DDR2-800, but only supports dual channel up to DDR2-667. But, if that is a limitation of your mobo, then perhaps there is something that a BIOS update might fix.

5. Both trains will arrive at Disneyland at 12:00 EST. :kaola: 
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August 3, 2011 7:45:20 PM

I downloaded a trial version of Aida 64 to see if I could find anything useful there.


One of the PC2-6400 dimms shows: Module Size 1 GB (1 rank, 8 banks)

while all of the other dimms, including the other PC2-6400 stick show: Module Size 1 GB (2 ranks, 4 banks)

Could this be why the PC2-6400 dimms won't run in dual channel mode when I put them in there by themselves?

I bought these as a matched pair.

Part NO. MD2048KD2-800 as far as I can determine. The PNY website is anything but helpful.


Daniel

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Best solution

a b } Memory
August 4, 2011 1:15:58 AM

The DDR generations of RAM are 64-bit wide addresses for non-server RAM. DIMMs are built using "×4" (by 4) memory chips or "×8" (by 8) memory chips with 8 DRAM chips per side. "×4" or "×8" refer to the data width of the DRAM chips in bits.

The term "Rank" means the collective amount of DRAM chips per side; whereas the term "Bank" identifies how many "grids" per chip.

So, assuming that all sticks are double sided with a x8 organization, the one stick being reported as 1 Rank, 8 Banks has 8 chips on each side. Each of these 8 chips would have a 4-bit-wide data bus, and the 8 4-bit chips have 8 grids. The other three would have 8 DRAM chips on each side, with each chip 8-bits wide, but only 4 grids.

What this effectively means is that the lone 1-8 has only one 64-bit side to read/write from, while the three 2-4's have two 64-bit sides to read/write from.

Dual channel technology allows up to 128-bit data transfers, but if one stick only has 64 bits to address, then this certainly would explain why the pair of PNY sticks will not work in dual channel mode.
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August 4, 2011 3:09:32 AM

Sounds like this one is solved.

Still a few lingering questions though.

Do the the x4 and x8 dimms physically look the same?

How the heck can they sell me a matched pair that don't match?

How did dual channel mode work in my old computer? (pretty sure it said asynchronous dual channel or something of the sort, it's been several months since I had the old computer hooked up)

Could Aida be wrong?


Daniel
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a b } Memory
August 4, 2011 5:17:08 PM

devans said:
Sounds like this one is solved.

Still a few lingering questions though.

Do the the x4 and x8 dimms physically look the same?

Yes. the x4 and x 8 grids are not seen, they are a part of the physical DRAM chips you would see on the side of the RAM, provided the DRAM chips aren't covered with a heat spreader (as they are with high performance/gaming models)

devans said:
How the heck can they sell me a matched pair that don't match?

You'd have to talk to PNY about this one.

devans said:
How did dual channel mode work in my old computer? (pretty sure it said asynchronous dual channel or something of the sort, it's been several months since I had the old computer hooked up)

Could Aida be wrong?


RAM scanners read off of the Serial Presence Detect chip on the RAM modules, but that doesn't mean that the software is immune to failure. Get a second opinion by downloading, installing, and running CPU-Z. Check the Memory tab and the SPD tab.


Daniel[/quotemsg]
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a c 347 } Memory
August 4, 2011 5:56:49 PM

Your MOBO DIMM installation is 'ass-backwards' to most others -> http://support.dell.com/support/edocs/systems/insp531s/...

CPU: | Set 2 Ch0 | Set 2 Ch1 | Set 1 Ch0 | Set 1 Ch1 | ; simply Ch0 size = MUST = Ch1 size, but and added factor is the SAME TYPE; 512MB and 1GB are NOT the same type e.g. SS vs DS.

Some older MOBO's and CPU, I consider AMD Athlon 64 X2 5600+ old, are even more 'touchy' and the other factors can easily kill Dual Channel.

9.999/10 if you are MIXING 512MB SS and 1GB DS that will not Dual Channel :( 
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August 6, 2011 11:15:07 PM

Best answer selected by Devans.
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February 14, 2014 12:22:40 AM

hello all
even i'm having the same problem
cpu : apu a10 7850k
mobo : asus a88xm-a
ram : cmz8gx3m2a2133c11

dual channel not working..
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