Question Mixing 4x8gb ram with 2x16gb ram

[jv2019]

Hi I'm buying a pc running Ryzen Threadripper 2970WX on a Asrock fatality x399 motherboard, comes with 2x8gb of ddr4 3200mhz ram ( no option for 2x16) can I add another 2x8gb and 2x16gb of same brand and speed ram and have it all running optimal for a total of 64gb? and what would be the best slots to do so? ( I'm not a computer expert or builder, but understand a little)

I'm thinking if it would be possible to have the 4x8gb for now + the 2x16 (64gb) with the option to expand for another 2x16 in the future for a total of 96gb, but not sure if that would make the memory not run at top performance

thank you!

 

[ElectrO_90]

Mixing ram is NOT recommended, because it works sometimes and sometimes it does not, even if it's from the same manufacturer.

 

[13thmonkey]

Mixing kits is not guaranteed to work, you might get lucky (some do, some don't), even if they are the same make and model, unless they come in a pack together you are chancing it.

 

[jv2019]

Mixing kits is not guaranteed to work, you might get lucky (some do, some don't), even if they are the same make and model, unless they come in a pack together you are chancing it.

I mean using them in pairs, the board accepts dual channel and quadchannel. For the 1st 4 slots use the 2x8 gb that comes with the computer and add another 2x8 of the same make model ( corsair vengeance lpx 3200), and wondering how best to populate the other 4 slots; original plan is a 4x8gb kit, my previous question was if I were to get 2x16gb kit for now would that work fine... I downloaded the motherboard specs, looks like it is a no ( see below).
I hear you on using different kits is chancing it...but I'll just have to do it for the extra 2x8gb on the 1st 4 slots and hope they work in quadchannel, but if not I'm guessing worst case they will work in dual channel separately? is that even possible? - just don't want to lose the memory that comes with it and have to replace for a 4x kit-

I will get a 4x8kit for the other 4 slots, just wondering if even then I can have problems. Any knowledge on this?


manual of the Asrock fatality x399 can be found here:
http://asrock.pc.cdn.bitgravity.com/Manual/Fatal1ty X399 Professional Gaming.pdf

page 20 shows it should be populated in 2, 4 or 8 dimms.

hope this is clear

thanks for the help!

 

[13thmonkey]

Still not guarenteed to work, they have to work as a set, all 2/3/4/8 however many you are fitting.

 

[jv2019]

Still not guarenteed to work, they have to work as a set, all 2/3/4/8 however many you are fitting.

I get the standard rule of not mixing memory, it makes sense for dual channel on motherboards with 2 slots or 4 slots, and I also get the risk of mixing 2 kits of 16gb (2x8gb) or 2 kits of 32 (2x16gb) as they may not work in quadchannel

but I do not understand why all pieces have to work as a set on a 8 slot motherboard (there is no "octa" channel). If technically the motherboard has 8 slots and offers dual, triple and quad channel, why can't I get a kit of 64gb (4x16gb)for example filling 4 slots in quadchannel, and have the other kit of the existing 16gb( 2x8gb) filling 2 slots and working in dual channel mode?
what would be the cons?

also it would help to have someone that has used this board with threadripper to give some input on this, have you?

thank you!

 

[13thmonkey]

The cons are simply that it may not work without substantial fiddling with sub timings and voltages.

https://www.scan.co.uk/products/64g...Nc3mljebJiCctxuBWWBH4VC0zqXjfX2saAoQYEALw_wcB

https://www.scan.co.uk/products/128...Cfqs7yJIiOxLyCkCfsDlxEghk0d5Qo5gaAliYEALw_wcB