I don't know it the image sbelow are too much info, or too little. Feel free to correct me.

I have a desktop which I use only as a file serve/continuous backup.

It is runnig slowly and I thought that could benefit from more RAM (agree, or do I need a new motehrboard?).

It has 2 @

Capacity 4 GB
Manufacturer Kingston
Model 99U5584-005.A
Type DDR3 / PC3-12800

and two empty slots. I was thinking of adding 1 @ 8gB, which ought not to be too expensive & see it perfomance improves.

BUT, I can't find an exact match for the current RAM.

What to do?

  • new motherboard & RAM?
  • new, non-matching, but compatible RAM? Which?
  • repalce all RAM? with what?

I hope that this is enough info :

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2 Answers 2


First of all: using the "same" memory (manufacturer, rated frequency and timings etc.) still does not 100% guarantee compatibility, especially if you are adding a DIMM with higher capacity. So when searching for DIMMs to upgrade, I would not focus too much on names.
The DIMMs you have already are most likely single-rank. For upgrading memory, you basically have two options. Technically more if you don't care about performance and feel adventurous, but I'll stick to those 2.

1) Add another 8GB DIMM (preferably dual-rank) into one of the slots currently occupied by a 4GB DIMM, and place that one on the same memory channel as the other 4GB DIMM. Check your motherboard manual which DIMM slot belongs to which channel. This will ensure a balanced memory configuration, despite different DIMM sizes. I.e. same amount of memory (8GB) and same amount of ranks (2) on each channel.
2) Add two 4GB DIMMs (preferably single-rank) to the empty slots. This again results in the most balanced memory population possible. This would be my preferred option.

If you stick to those rules, you have a good chance of avoiding compatibility issues, despite using different DIMMs. As far as the rated specs are concerned: try to stay as close as possible to PC3-12800 CL11 as possible. The name of the brand that put its sticker on the DIMMs is of minor concern for compatibility.

As far as "will this improve performance, or do I need to upgrade the CPU instead" goes: This would require a lot more information about the kind of workload you have. But you can check it yourself, by monitoring CPU load and memory consumption. From the last image you posted, it does not look like memory capacity is a problem, only 5.5GB of 8GB are used. Be careful though, single- or lightly threaded tasks can be CPU-limited, despite not showing 100% utilization.

  • Thanks muchly! "This would require a lot more information about the kind of workload you have" - I have 6 harddrives, which I use for continuous backup from 2 laptops. "From the last image you posted, it does not look like memory capacity is a problem, only 5.5GB of 8GB are used" - so, new CPU and/or motherboard? I am looking for a cheapish solution and would hate to throw away working motherboard & CPU & RAM. 2@ used 4gB RAM are cheap enough, so I will probably try that first Feb 29, 2020 at 11:13
  • 1
    You can try more RAM if you consider it a cheap experiment. It might help if that screenshot was not taken at an instant when performance was low. Unfortunately, CPUs for the FM2+ all fall in the same ballpark for single-threaded performance. If single-threaded performance is not the issue with your workload, then using a CPU with 4 cores might help. But overall, I think a little more diagnosing of what is actually the bottleneck would go a long way. It might even be something other than RAM or CPU. Hardware recommendations is just not the place for it, the mods here run a tight ship ;)
    – user13807
    Feb 29, 2020 at 12:06
  • Thanks very, very much for your help! I imagine that SuperUser might help with further diagnosis. But, as RAM is so cheap, I will try that first. Feb 29, 2020 at 13:20
  • while RAM is cheap I don't think it is likely to not solve your slowness. Spending a little extra on a good NAS with all the features they provide I think would be the best solution especially if you value performance and reliability. I would not waste the money on DDR3 RAM on an old socket FM2 mobo.
    – ron
    Mar 1, 2020 at 1:20
  • A little extra ?? A cheap NAS costs hundreds - unless you can recommend something truly cheap, this is 500% or more of the cost of the RAM (I suppose that I can make one with a Raspberry Pi, but they don't have many USB ports (perhaps a shield?)) Mar 18, 2020 at 13:00

Your motherboard manufacturer Gigabyte recommends a pair of matching DDR3 2400(OC)/2133/1866/1600/1333 MHz dual channel memory modules, up to 32 GB each. AMD Memory Profile (AMP)/ Extreme Memory Profile (XMP) memory modules are accepted.

Gigabyte published a list of qualified memory modules from 1 GB - 8GB in size for your review.

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