Questions about mixing RAM brands/sizes.

[mgb_]

I have two machines with 4GB (2x2GB) of RAM in each, they are different brands but look to be the same spec. I need to upgrade to 8GB in one of the machines and it wouldn't hurt to upgrade the other. I noticed for almost the same price I can get 2 x 4GB of another brand for the price of 2 x 2GB of the two I already own. So, here are the questions:

 

Can I combine the two different brands i already have (2 Corsair x 2 Kingston x 2GB) into one system?

 

If I can combine them would it make a difference as to what system I put the unmatched pair into? (The two systems and their uses are below)

 

If I can't combine them what are the drawbacks, if any, of having the same brand but different size sticks? Like 2 x 2GB and 2 x 4GB sticks bringing the total to 10GB or or maybe 2 x 2GB and one 4GB to bring it to 8GB if thats better for some reason?

 

 

System 1:

HTPC running Win7, GIGABYTE GA-H67MA-UD2H-B3 motherboard.

 

system 2:

Media/File server running unRAID, MSI 880GMA-E53 motherboard.

 

 

 

Memory 1:

CORSAIR XMS3 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMX4GX3M2A1600C9

 

Specifications:

http://www.corsair.com/us/cmx4gx3m2a1600c9.html

 

New Egg Link:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820145260

 

 

Memory 2:

Kingston HyperX Blu 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model KHX1600C9D3B1K2/4GX

 

Specifications:

http://www.kingston.com/datasheets/KHX1600C9D3B1K2_8GX.pdf

 

New Egg Link:

http://www.newegg.com/Product/Product.aspx?Item=N82E16820104203

[garycase]

Can I combine the two different brands i already have (2 Corsair x 2 Kingston x 2GB) into one system?

 

Yes, you can simply put all 4 modules in the same system and have 8GB using 4 2GB modules.  HOWEVER, I don't recommend doing so.  Here's why:

 

With unbuffered memory systems, you'll have far more reliable memory if you only install 2 modules.  The signal degradation from the bus loading with 4 modules installed can have a notable impact on the system's reliability;  and this is especially true with high-performance modules that require higher-than-normal voltages, which both sets of these do [they're 1.65v modules;  the standard DDR3 voltage is 1.5v].  I suspect you've been running these at the wrong voltage -- voltage is NOT an SPD parameter, so unless you changed the BIOS to use the correct voltage, you've been running them at 10% undervolt 

 

I'd buy a pair of 4GB modules for each system and have 8GB with only 2 modules.  This will be more reliable than using 4 2GB modules.    Note that the Gigabyte board supports 8GB modules, so if you wanted to you could install 2 8GB modules (total of 16GB) in that system while still only populating two slots.    In either case, I'd buy standard 1.5v modules.

 

 

If I can combine them would it make a difference as to what system I put the unmatched pair into? (The two systems and their uses are below)

 

You don't have an "unmatched pair".    You have 4 modules with the same specifications.  In fact, you lucked out, as BOTH pairs use a non-standard 1.65v (the standard DDR3 voltage is 1.5) ... so if you DO choose to install them all, you can set the voltage in the BIOS to the correct voltage for the modules.

 

 

If I can't combine them what are the drawbacks, if any, of having the same brand but different size sticks? Like 2 x 2GB and 2 x 4GB sticks bringing the total to 10GB or or maybe 2 x 2GB and one 4GB to bring it to 8GB if thats better for some reason?

 

As long as you install the RAM in pairs [i.e. a pair of 2GB modules and a pair of 4GB modules], you're fine IF you're running modules that require the same voltage -- so you'd have to buy 1.65v modules for the 2nd pair.    But I don't recommend doing this for the same reasons I outlined in the answer to your first question.

 

[garycase]

... just to be clear, my recommendation is that you sell all of your existing RAM and simply a pair of larger capacity modules for each of your systems.

 

If you don't want to do that, then put all 4 of your current modules in one of the systems;  go into the BIOS and set the memory voltage to 1.65v;  and then buy a pair of 4GB modules for your other system.    ... if you notice "random" stability issues on the system using all 4 modules, then either remove two of them;  or remove them all and buy a pair of higher-density modules for that system as well.

 

[kabadisha]

I just wanted to drop here and say thanks to @garycase and leave this here in the hope that it will help others in the future.

 

I recently started seeing parity sync errors on an array with disks that all seem happy otherwise. I've been tearing my hair out trying to figure out why they keep coming back (around 700 errors on a 30TB, 3 x 14TB disk array).
Having stumbled across this thread, I double-checked my RAM and bingo! - I mixed RAM with different specs as it's what I had on-hand. Crucially, half was rated for 1.5v and the other half wanted 1.65v. They also had different timings.
I've just removed half of it, manually set the correct voltage & frequency in BIOS and am re-running parity sync now. So far it seems like much lower error rate, so I think I've found the problem 🙂

I'll run another parity check after this one completes and fingers crossed, I'll get zero errors on that run.

Thanks again!

Edited October 12, 2022 by kabadisha
Grammar improvements

[Lolight]

5 minutes ago, kabadisha said:

I've just removed half of it, manually set the correct voltage & frequency in BIOS and am re-running parity sync now. So far it seems like much lower error rate, so I think I've found the problem 🙂

Glad you've solved the problem.

I just want to point out that the best way to make sure that the are no memory related problems, on any system, old or brand new,

is to run several passes of Memtest86+ (at least 4).

If finished without a single error only then you can consider your memory (or configuration if multiple sticks) to be NAS worthy.

[kabadisha]

Yeah, that's a good shout - I'd seen that advice elsewhere regarding parity sync errors which is what led me down the RAM research rabbit-hole.
Oddly, after ripping out the offending RAM I did attempt to do Memtest as you say, but when I selected that option from the unRaid boot options the machine simply rebooted with apparently no attempt to launch memtest.
I suspected it was something to do with my LSI HBA interrupting the boot process, but didn't have time to dig into it.
I've just ordered a couple of larger RAM sticks to replace what I am left with right now, so will try again to run Memtest when that arrives.

[Lolight]

4 minutes ago, kabadisha said:

Oddly, after ripping out the offending RAM I did attempt to do Memtest as you say, but when I selected that option from the unRaid boot options the machine simply rebooted with apparently no attempt to launch memtest.

Interesting that you've mentioned that.

The same thing had happened on my recent new build - an immediate reboot after selecting Memtest from the Unraid boot options.

I don't have an HBA card so it's unrelated.

i also didn't bother troubleshooting and simply booted from another USB stick with Memtest on it.

[JorgeB]

Memtest boot option only works for CSM boot, it won't with UEFI boot.

[kabadisha]

1 minute ago, JorgeB said:

Memtest boot option only works for CSM boot, it won't with UEFI boot.

Oh that's excellent to know! Thanks for the tip 🙂

[Lolight]

Just now, JorgeB said:

Memtest boot option only works for CSM boot, it won't with UEFI boot.

That was a quick and easy answer!

Nice to have a real guru around! 👍

[kabadisha]

Just an update to confirm that the RAM was indeed the issue. Removed it and after one cleanup sync, the second sync returned no errors!

Woohoo!