Hello guys, I have bought and will receive soon a new 5K, 27-inch 2017 iMac 18,3. Like any sane person I didn't BTO bump the system base 8gb RAM because price, but now I'm having trouble finding the desired upgrade: the mac ships with 2x4gb, but on Crucial.com the smaller upgrade is the single 8gb bank; there goes my plan of doubling the RAM to 16gb total, buying a 2x4gb kit. I could go for 24gb total buying a 2x8gb kit (I know there's a and I'd be okay with that), but that's kinda beyond my needs and expected budget.

So the real question: would a 4gb + 4gb + 8gb setup (buying a single 8gb bank) have horrible performance? Is that the stupidest idea ever? Thanks a lot for any input!

So the real question: would a 4gb + 4gb + 8gb setup (buying a single 8gb bank) have horrible performance? Short answer: No. Long answer: As long as you don't rearrange the memory, you will still be in dual channel mode, using dual channel for the two matching sticks and single for the unmatched. This one is from a specific motherboard, but it's a consumer desktop product and the memory controllers are on-chip these days, so the information is broadly applicable, at least until we get to the triple- and quad-channel parts. In this case you are still using the second channel, you just aren't able to interleave memory (Like RAID 0 for RAM) for the additional RAM.

So some things like the core OS will occupy the lower memory and receive the benefits of dual-channel memory. As you start to chew up more RAM, data will end up in the single-channel memory space. Real-world performance difference for one-stick vs. Two-stick tends to top out at 10%. Typically, the loss of dual-channel only matters in memory-intensive applications. Processors have several layers of cache and predictive fetch logic to avoid waiting on calls to main memory as much as possible, so tasks like processing large (multi-gig) datasets see big impacts, but even video rendering is only affected by a few percent.

2x4gb Ram Ddr3

The greatest performance impact is for processors with integrated graphics, because they have two separate 'components' on the processor accessing memory at the same time, so the additional bandwidth is really needed. All of the 27' iMacs have discrete graphics. I do not think the integrated graphics on the processors are used for any tasks, but I am not certain. Just a little follow-up: I decided for a 4 4 8 8 configuration, for a total of of 24GB. I still think it's overkill for my current needs, and rarely managed to fill the RAM during normal workload so far, but I didn't want to miss out on dual channel, and this way the machine (which is brand new) should be a little more future-proof.

I followed your indications in, matching the same-size banks on the same DIMM slots (this took two tries, as the slots are counterintuitively alternated, like this: ) Thanks again for the big help! Thanks a lot for the thorough answer, appreciate the input. Reading through it I realized I might be an edge case tho, as I use the Adobe Creative Suite a lot and the 16gb on my current machine are very often completely busy. But this never really had a terrible impact on my current Fusion Drive iMac performances. My wild guess, from experience, is that also having a lot of webpages open all the time (for webdesign needs) I'd likely fill 24gb in a heartbeat too, that leads me to the idea of saving some bucks and going for only 16gb total (I could buy a second 8gb bank at any time to double the upgraded one). Again, real world performance impact is going to be something like a 3-5% performance impact, and that is comparing the same amount of memory, installed differently.

A system with unmatched RAM but 16 GB is still less memory constrained. Memory is still much faster than hard drives, even SSDs. The newest SSDs are pushing around 2 GB/second.

That's the performance limit of the original DDR memory from the year 2000. Modern DDR4 starts at 7x that performance limit. Running the RAM 3-10% slower than possible is still far better than having to page files to disk. Honestly, in my experience with these models it's a very bad idea to combine Apple ram + 3rd party ram, especially if the sizes differ. The amount of iMacs that come in for repair that had the above done with weird freezing/crashing/file corruption issues is just so much, most customers aren't even aware it's their usually harmless upgrade causing the problem. Of course there are some that have had success with this, and hell, you may have success with it too, but the issue with this might not become apparent immediately and may lead to data loss once file corruption occurs, your Mac can no longer boot from the HDD and a reinstall will be required to get it up and running again.

I'd advise against your suggested configuration and go for new 16GBx2 or 8GBx4 Ram sticks. An Apple techs 2 cents.

Inactive memory used by recently active and quit apps. OS X keeps it reserved in case the user wants to open the program again. If it happens, OS X does not need to relocate memory that accelerates performance speed. If you do not re-open the program, after a while the memory of the inactive will be freed or relocated. There are situations when you do not have enough memory for a good performance, thus you need to free up memory on Mac as soon as possible. To do this, you have to clear the inactive RAM. Today we will tell you three methods how to clear RAM on Mac.

Fs: General 2x4 Gb Ram For Macbook Pro

Way 1 – Use Terminal Start the Terminal application, default app on every Mac. Then enter the following command sudo purge Next, the system will ask you to enter a password, after being entered inactive memory will be cleared. Pros and cons Pros: you use a standard method without any additional software. Cons: free up the process in such a way definitely slows down your system. As well you have to re-open Terminal and enter the lines once again.

Firstly, it is not convenient, secondary, if the system is already slowing down, opening another app takes time. Way 2 – Use Script Editor To use this method you have to be a developer 🙂 But don’t be afraid, in this case, you just have to follow our rules. Launch Scrip Editor In an opened window it will look something alike: Write down the following text. After press ⌘+S and save your script in Applications folders. Choose Application format instead of Script. Pros and cons Pros: Fancy creation process using standard tools, special app without a necessity to write commands in Terminal every time.

Cons: Still you have to launch an app, any time you have to clean up RAM, that is not always easy. Way 3 – Use Memory Cleaner We have created a special COMPLETELY FREE app to free up inactive memory to enhance a performance of your Mac. FREE After being launched the app constantly will be active from the Menu Bar. Displaying used memory in percentage or Mb (as you wish). If you see that index surpasses required value, simply click “Cleanup” and the app will do the rest (clear RAM on Mac).

Moreover, Memory Cleaner can clear the memory automatically, so you do not have to do it manually. In the settings of the app, you can set the frequency and when to perform auto cleanup. Also, the app allows to clean memory if you quit a big app. Thus, the program supports stable operation of your system. Video Tutorial How to Get More RAM on Mac See more. Prev:. Back:. Next: Related entries.