Optiplex 7010 2x8gb not running in dual channel

It says

"dual-channel mode is always present when both memory channels are populated. however, for optimum dual-channel performance, the size of the modules must match."

I've got matched sticks in the right channels, and they're both showing up and running fine, but they're in single channel instead of dual channel.

Have a look at this post. A lot of great information about RAM configuration.

Are the 2 modules (8GB each) the only memory, or do you have other modules also?

Exactly what are the brand and model of these modules?

Incidentally, the speed gain by having dual channel is very slight for most applications, so you probably wouldn't notice the difference if you do get it solved.

I only have the 2x8 in the system.  This is the model I'm using https://www.amazon.com/gp/aw/d/B007HZTD86?psc=1&ref=ppx_pop_mob_b_asin_title

I was previously running similar 2x4 sticks and they were working in dual channel.

certified ram looks like this.

https://www.crucial.com/usa/en/compatible-upgrade-for/Dell/optiplex-7010-%28mini-tower%29

ok, did you first RTM read you manual to see how to populate the slots for 1x8GB? that is first

then pull the AC line cord, first. and then push power button 3 times for 1sec, until fans stop twitching.

now the PC is 100% dead, never hot swap ram or BOOM go broke. fast.

then put in the sticks in the correct slots A and B.  do not guess, RTM.  the book even tells you slot colors in most cases.

then power up system

and reset BIOS,  hammer F2.  and reset bios,  (shows set bios to defaults) this will force a full DDR scan!

turn off PXE, feature in F2 BIOS, and make sure boot order is HDD0 SSD0 first.

then boot PC.

The 7010 MT has 4 DDR slots,  (no pc stated by you, and not reading all 4 manuals to you)

MT page 14 states.

Memory modules must be installed beginning with the first socket. (means A1 i presume)

The memory sockets in your computer may be labeled differently depending on the hardware configuration. For example, A1, A2 or 1,2,3.•
If the quad-rank memory modules are mixed with single or dual-rank modules, the quad-rank modules must be installed in the sockets with the white release levers.•
If memory modules with different speeds are installed, they operate at the speed of the slowest installed memory modules.

given the words on page 14, put one stick on A1, white ended slot, then stick 2 in B1.

A means channel A

B means channel B

so done that way and resetting BIOS, you will get , dual channel operation.

just off hand(cant see inside your PC) you are not using the 2 white slots.?

outboard to inboard are (slots labeled as DIMM1,2,3,4 but in this order)

2white (here)

4b

1w  (here)

3black

or here , no pc stated, but here is MT/DT

are both sticks same brand ,same maker and SKU?  "identical"

this is why buying real certified DDR is best. for 7010 called  16GB kit.

Alright, I think I may just have them in the wrong DIMMs. It's frustrating that the manual doesn't actually state which slots to use.  I'll try swapping them later.

Ah, that could be your problem. Patriot memory and Kingston memory are no good and rarely works properly in dell computers. Nobody knows why, but rock musicians always recommend  only crucial brand memory ... It's guaranteed to work with dells.

Patriot memory will NEVER work in any dell computers. Never ever.

This is late but is the 2 x black channels for dual?

I need to swap later on. 

I think my single channel is in the white channel. Need to lift up the disk drive. 

Sorry if I confused this topic. I meant double sided ram. 

@Maho Jakobic 

Maho, you are correct. I have since used several brands of memory. They seem to work fine ... to my great surprise. My computer seems to work with forbidden brands and forbidden sizes.

But most all the famous Rock musicians here do say it is impossible at best, and a disaster at worst.

But if you need to be on the safe side, still best to buy only genuine crucial brand (or adata if you're really broke). Never buy hynix or kingston value ram. These brands do not work in dells. EVER.

quad rank , high density and registered/buffered modules are not supported.

The slots with white ears are bank 0

The slots with black ears are bank 1

The order is slot 1 then slot 3   slot 2 then slot 4

Not 1 2 3 4

Only a genuine Dell Rock musician can answer. Perhaps one will grace us with their presence soon. You'll know when you hear the guitar riff.

All I can say is that dell computers seem to be special and are VERY picky about memory, and if you don't follow exact rules, no memory will EVER work.