Look at the other threads here in the Synology forum. Look where folks have DSx18 models and added RAM. Ask them what they bought. This is a very friendly and helpful group of people
I’ve been running the 918+ with stock ram of 4 gig running plex 64bit and no issues at all with 3 iOS devices and 2 nvidia shields and a Mac mini with plex media player. So far no issues as far as I can see.
@audiomixer @ChuckPA Dang I have no idea what else I could do to improve my stream… My iOS devices run smooth and I would say the most part when I’m watching on my tv using the plex app too. but from time to time I get terrible buffer, Is the difference between the 418play and 918+ that great? If you can think of anything I need to enable or should check please let me know.
@audiomixer @ChuckPA ok I may have found part of the issue… (facepalm)… I am currently only running 2gb of ram! this make perfect since now. My device is struggling to preform. Just to verify I can max the 418play with 8gb of match ram? Please correct my if I am mistaken. Thank you for your help. 
Here’s how to verify what we’ve told you about memory.
- Google “What CPU does my Synology have”
- Click the link which takes you to the Synology site
- Scroll down to your model number
- Look at the CPU number
- Google that number
- Click the link which points to
ark.intel.com(The link usually has your processor name in the title) - At the Intel page, scroll down to Memory Specifications
- You now see the total memory the CPU can address as well as the specifications for the memory module
Now you need to look at the Synology page again and see if it has 1 or 2 slots. Most have two.
This said, if 8GB is the maximum, obtaining 2 4GB modules is ideal. You remove the factory module and install both of the new 4GB modules
Thank you @ChuckPA
You’re welcome. See how easy it is?
@ChuckPA well when I have such extraordinary guidance from yourself it super easy. Haha thank you sir. I hope the weather is treating well.
The temperature here today is above freezing . This is a good sign. We will see how long that lasts. HAHA
@ChuckPA is there anything wrong with simply getting a second 4gig oem synology module other than perhaps price? https://www.bhphotovideo.com/c/product/1364352-REG/synology_d3ns1866l_4g_4gb_ddrl_ram_1866.html
There’s nothing wrong with getting the 4GB module in this case because, IIRC, the unit has two DIMM slots and 2 x 4 = 8 the last time I looked )
If your unit came with 2GB, you’ll end up with 6 GB. Any memory configuration which isn’t a binary boundary (e.g. 4, 8, 16, 32, etc) and constructed from two same-specification memory modules, can’t take advantage of the “Dual channel memory mode” the CPU is capable of. This is why you see “Matched Pair” and “Memory upgrade Kit” . (Both modules in the kit are the exact same specification from the same production batch and therefore have the same performance … The CPU will detect that)
Dual channel mode means exactly what it sounds like. The CPU can perform two memory operations concurrently. It doesn’t happen with every memory access but it occurs enough to be worth the effort up front. Video is all about moving data around. Video images are a big blocks of integers. If it’s possible have the CPU read from one DIMM while writing to the other… Go for it. Also, when the disk controller is depositing data directly in memory, it can interleave this without the CPU even knowing it. 
The typical result you’ll get is about 10%. It can be more but typically is around that mark
I saw this on amazon and appears to be a easy solution. Price appears to be the going rate. Unless you know of a better location.
Crucial 8GB KiT (4GBx2) DDR3/DDR3L 1866 MT/s (PC3-14900) Unbuffered SODIMM 204-Pin Memory - CT2K51264BF186DJ https://www.amazon.com/dp/B00N5UFBME/ref=cm_sw_r_cp_api_un-RAb42QJDFF
Now you have it!
I use Kingston in my DS1815+ and Corsair Vengeance in my desktop. I’ve not opened the QNAP (i7-6700 ) to see what’s in it yet
@ChuckPA my 918+ came with the single 4 gig module and that is why I was thinking of getting another synology 4gig module which “should” be the same as the original.
So the link that gcooper shows, what is the difference with this one? https://www.amazon.com/Crucial-PC3-14900-SODIMM-204-Pin-Memory/dp/B01979WV9C/ref=sr_1_6?ie=UTF8&qid=1521477231&sr=8-6&keywords=1866+ddr3l&refinements=p_89%3ACrucial|CRUCIAL+BY+MICRON+-+DRAM
On edit, the only difference I can find is that the more expensive (CT2K4G3S186DJM) one is a lead free Halogen free design vs the regular one CT2K51264BF186DJ. Is that right? I found this on the crucial web site.
If it came with that same 4GB module then you’re OK.
Some of them come with 2GB modules. This is why I raise the caution.
One ‘ding’ at Synology, you don’t know the anything more than the main ‘1866’ spec. On each DIMM is a SPD module which controls CAS,RAS,CL, and all the other timing parameters. The CPU will pick the slowest value set. Personally, that’s a gamble I don’t take when I"m building/upgrading anything. I expect a level of performance, whatever it is. Being the engineer I am has taught me to keep like-specification parts together.
I might be outdated, I might not. If someone can educate me, I will gladly learn and amend any comments I’ve made.
Ok, yes, that sounds totally reasonable.
