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For 32gb total: 2x8gb now and add 2x8gb later? Is this okay?

408 views 15 replies 6 participants last post by  s1rrah 
#1 ·
Hi ...

Was talking with a friend about this and am curious. I'm building a new rig (6700K) and have currently purchased a 16GB (2x8GB) Corsair Dominator kit. If I'd like to go 32GB later, could I simply purchase another 2x8GB kit and plug in to my other two RAM slots? Would this run okay?

We were thinking it might be best to order a proper "quad" 4x8GB kit but is this really true? Would there be any issues just waiting and adding another 2x8GB kit down the road?

Thanks for any input....

joel
 
#2 ·
It's a crap shoot whether buying a second 2 x 8 Gig later will work. Even if you buy the same moded and part number the may not match because memory manufacturers randomly change ICs.

Fortunately Corsair does a pretty good job by adding a "Rev #" to the part number when they change ICs. But you'd still have to locate a second set with the same Rev# as the original and that may be difficult.
 
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#3 ·
Even if they have the same Rev #, it doesn't mean they will run together at rated speeds. The sets are rated on their own and not checked in 4 DIMM setups when you buy 2 DIMM kits.

If you think you will ever exceed 16GB memory usage during the lifetime of your PC, then go straight for 32GB. If not, then taking the chance on going 16GB is probably a good money saver.
 
#4 ·
Pardon me, I interested to ask question in this thread.
Quote:
Originally Posted by Shaded War View Post

Even if they have the same Rev #, it doesn't mean they will run together at rated speeds. The sets are rated on their own and not checked in 4 DIMM setups when you buy 2 DIMM kits.
I don't understand. So if I have 2x4GB 1600MHz DDR3 RAM, and I add the same 2x4GB 1600MHz DDR3 RAM later. The later pair will not run at the same speed (1600MHz) like the first pair or?
 
#5 ·
Quote:
Originally Posted by Maggots View Post

Pardon me, I interested to ask question in this thread.
Quote:
Originally Posted by Shaded War View Post

Even if they have the same Rev #, it doesn't mean they will run together at rated speeds. The sets are rated on their own and not checked in 4 DIMM setups when you buy 2 DIMM kits.
I don't understand. So if I have 2x4GB 1600MHz DDR3 RAM, and I add the same 2x4GB 1600MHz DDR3 RAM later. The later pair will not run at the same speed (1600MHz) like the first pair or?
It might work fine. But the kits were not tested together when they were made, so there is a chance it won't work. I'v had some kits work together, but allot of them don't.
 
#6 ·
Quote:
Originally Posted by Shaded War View Post

It might work fine. But the kits were not tested together when they were made, so there is a chance it won't work. I'v had some kits work together, but allot of them don't.
I've had the same experience. I first built my daughters rig with 2x4GB sticks and recently purchased another 2x4GB of the same matching RAM. They refuse to work together w/o constant BSOD's. Either 2x4GB works fine if that is all I install but together it is a no go.
 
#7 ·
Background:

When a computer posts the BIOS reads the speed and timings that are programmed into the memory stick that is installed closest to the memory Controller (ie. to the CPU). The BIOS than applies that speed and those settings to all the memory that is installed.

Of course you can manually set the speed and timings. But if what is programmed into the sticks differes to much from each other you may have to sacrifice some performance to get then to all work together., and there's the possibility that may be very difficult to do or even possible.
 
#8 ·
Quote:
Originally Posted by Shaded War View Post

It might work fine. But the kits were not tested together when they were made, so there is a chance it won't work. I'v had some kits work together, but allot of them don't.
This is the first time I heard this really. Because for many years I usually add more RAM on regular work PC if it turns out that there is insufficient memory to run a certain application, even with different brand of RAM a few times. And it's never been any issue. So I'm surprised that actually people has issue with their PC by adding more RAM.
Quote:
Originally Posted by BulletSponge View Post

I've had the same experience. I first built my daughters rig with 2x4GB sticks and recently purchased another 2x4GB of the same matching RAM. They refuse to work together w/o constant BSOD's. Either 2x4GB works fine if that is all I install but together it is a no go.
Maybe you should check the with memtest86 first to check if there is problem with the later pair. Because I added my 2x4GB RAM with the same 2x4GB pair and it works fine.
 
#9 ·
Quote:
Originally Posted by Maggots View Post

Quote:
Originally Posted by Shaded War View Post

It might work fine. But the kits were not tested together when they were made, so there is a chance it won't work. I'v had some kits work together, but allot of them don't.
This is the first time I heard this really. Because for many years I usually add more RAM on regular work PC if it turns out that there is insufficient memory to run a certain application, even with different brand of RAM a few times. And it's never been any issue. So I'm surprised that actually people has issue with their PC by adding more RAM.
Quote:
Originally Posted by BulletSponge View Post

I've had the same experience. I first built my daughters rig with 2x4GB sticks and recently purchased another 2x4GB of the same matching RAM. They refuse to work together w/o constant BSOD's. Either 2x4GB works fine if that is all I install but together it is a no go.
Maybe you should check the with memtest86 first to check if there is problem with the later pair. Because I added my 2x4GB RAM with the same 2x4GB pair and it works fine.
The speed of the memory can also be a factor. When going over 1600Mhz on DDR3, it can be allot less likely to work. My last rig worked perfectly fine on a 2x4GB set mixed with a 2x8GB set at 2400Mhz and matching timings, but two matching 2x4GB 2400Mhz sets wouldn't work together even though they are identical part numbers. I'v also had matching kits of 1866 memory not work with each other on one system, but work fine in another.

In general, it's best to buy the memory you need in one kit instead of potentially causing issues.
 
#10 ·
No, your motherboard will explode.

tongue.gif


Realistically it should be fine in this day and age. The vast majority of motherboards will set the frequency to the lowest of all DIMMs and the latency to the highest. The only issue you should probably be concerned with is ranking. I can't find a better article, sorry, but the TL;DR is that single-ranked DIMMs have 8 memory packages and dual-ranked DIMMs have 16. Some very high capacities are always dual-ranked (since the memory chips aren't large enough for single-ranked to be possible) while other mid-tier capacities can go either way. Ranking's biggest impact is on memory refresh cycles, and there are some small performance increases with dual-ranked DIMMs if I remember correctly. With the popularity of stupid and unnecessary heatsinks on everything, it's hard to tell what you're getting though.

(I think, somebody correct me if I'm wrong.)
 
#11 ·
Quote:
Originally Posted by Shaded War View Post

The speed of the memory can also be a factor. When going over 1600Mhz on DDR3, it can be allot less likely to work. My last rig worked perfectly fine on a 2x4GB set mixed with a 2x8GB set at 2400Mhz and matching timings, but two matching 2x4GB 2400Mhz sets wouldn't work together even though they are identical part numbers. I'v also had matching kits of 1866 memory not work with each other on one system, but work fine in another.

In general, it's best to buy the memory you need in one kit instead of potentially causing issues.
Perhaps you right, maybe speed of RAM indeed also be a factor. And that issue perhaps occurred on RAM that have more speed than standard RAM. I can't really guest because I not yet have the experience to use much faster RAM than 1600MHz
 
#12 ·
Thanks for the replies and comments ...

I'm buying DDR4 3200 and want to overclock, even if a teeny bit so I'm sending the 16gb DUAL kit back and have already ordered a 32gb QUAD kit just to be sure ...

thumb.gif
 
#13 ·
Quote:
Originally Posted by s1rrah View Post

Thanks for the replies and comments ...

I'm buying DDR4 3200 and want to overclock, even if a teeny bit so I'm sending the 16gb DUAL kit back and have already ordered a 32gb QUAD kit just to be sure ...

thumb.gif
Good idea. Getting something at 3200Mhz to play well with mixed kits would probably be hard.

Personally, I'd have looked for a 2x16GB set for less DIMMs to stress the IMC if on a z170 setup. Otherwise if on x99, quad channel would be something you could take advantage of. Not sure how much a comparable 4x8 kit is price wise, but these are $170.
 
#14 ·
Quote:
Originally Posted by Shaded War View Post

Good idea. Getting something at 3200Mhz to play well with mixed kits would probably be hard.

Personally, I'd have looked for a 2x16GB set for less DIMMs to stress the IMC if on a z170 setup. Otherwise if on x99, quad channel would be something you could take advantage of. Not sure how much a comparable 4x8 kit is price wise, but these are $170.
So you think a 2x16 kit would be better for 6700K? Worth canceling an order and reordering better? LOL .. .if it's just an indiscriminate, "visible only on benchmarks" ... or a matter of a frame or two a second? Then I think I'd just stick with the quad ...

???
 
#15 ·
Quote:
Originally Posted by s1rrah View Post

So you think a 2x16 kit would be better for 6700K? Worth canceling an order and reordering better? LOL .. .if it's just an indiscriminate, "visible only on benchmarks" ... or a matter of a frame or two a second? Then I think I'd just stick with the quad ...

???
More DIMMs means more load on the memory controller, which can lead to needing more voltage when overclocking or potentially less overclocking headroom. Since z170 cannot use quad channel, there isn't any reason to go with 4x8GB over 2x16GB. But If you already ordered it, I would just stick with it.
 
#16 ·
Quote:
Originally Posted by Shaded War View Post

More DIMMs means more load on the memory controller, which can lead to needing more voltage when overclocking or potentially less overclocking headroom. Since z170 cannot use quad channel, there isn't any reason to go with 4x8GB over 2x16GB. But If you already ordered it, I would just stick with it.
That's what I decided ... I'll be happy if all of them run well at the advertised 3200 speed ... thanks for the comment.
 
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