Windows 10: Installed ram is dual channel 2666 and 3200 but CPU Z showing only 665.5mhz aprox

I have bought new laptop Dell inspiron 3501. This model support 2666 and 3200 mhz. There are total two slots availiable. In one slot i have installed samsung 3200mhz ram and in another slot it is 2666mhz ram. Now in task manager it shows 2666mhz speed. But when i check CPU Z application then it shows current DRAM speed is usable is only upto 665.5 aprox. Because i have installed two different ram so lowest speed should be considered i.e 2666 and because it is DDR it should show 1333 in DRAM in CPU Z. Why this is happening??????? I have fully updated my drivers, my bios and windows update. I am on windows 10 20H2 and os build is 19042.844




:)

 

16gig of ram installed (8.0gig usable)

Thanks for your response Greg.

Not sure of your suggestion of 'apportionment'.

-At the moment, all peripherals are removed from the suspect pc . All that remains is the OS drive and another graphics card, which is showing 4gig of resources in addition to its own 512mb. I'm using this card to test
in place of the better card I used, which has 2gb onboard.

-This Gigabyte GA-970A-DS3P motherboard has no onboard graphics nor does the AMD FX8320 CPU.

-The Memtest86 ran all night with no errors. The bios was

reset to default.

-The bios does show all the ram.

-I have exchanged ram with a spare pc. The ram from the suspect pc runs fine in the spare pc. The ram from the spare pc shows the same problem of half ram in the suspect pc.

-When I install two 4gb of ram in slot 1 & 3, Windows system shows all 8gb. When I begin adding more 4gb ram in slot 2 & 4, the unusable ram message appears.

- One curious observation is, the app CPU-Z, shows dual channel with ram sticks in 1 & 3. If I add to 2 & 4, CPU-Z begins showing single channel.

I haven't found any adjustments in the BIOS that can make any adjustments that have been suggested.

Thanks

 

Single vs dual channel RAM in a laptop

I have a new Dell Vostro 5590 i7 10510U laptop with 8GB DDR4 RAM 2666 Mhz and a NVidia MX250 GPU with 2GB. Win10 Pro. NVMe SSD.

The RAM is running in single channel currently. There is an available RAM slot that can be used to increase RAM. If I add another 8GB “stick’’ of DDR4 2666 MHz RAM (to total 16GB), I presume the RAM will then run in dual channel. Will this make the laptop faster overall?

Not because the laptop is slow, but I want to get the most out of it.

 

Can't Change RAM Frequency in Bios

Do you have a link to the specific RAM modules you have installed?

Also, run CPU-Z again, and this time post the "SPD" tab. This tell use what speeds the modules are capable in XMP. Here's mine....





My modules are rated at 3600MHZ, and going by the above - XMP shows 1798, but since the modules are running in dual channel that would be 2 x 1798 = 3596 (rounded to 3600)....