Apple uses RAM from a variety of vendors but primarily Micron, Hynix and Samsung. Depending on the date and location of assembly you could end up with any of the above.
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What Ram to order with the new 2019 IMac?
- Thread starter Potts17
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Apple uses RAM from a variety of vendors but primarily Micron, Hynix and Samsung. Depending on the date and location of assembly you could end up with any of the above.
That's true, but I think even for different RAM makes, the clock and CAS latency should be the same, knowing those specs is enough for matching when buying from 3rd party.
My question exactly - RAM that's available from (for example) Mr. Memory claims to be 100% compatible with the new iMacs, but is stated as being PC4-21300, as opposed to PC4-21333 which is what Apple state on their own page. Are the two interchangeable? Is it just a terminology thing, or are the two actually different?
They are slower (you won't notice) but are still supported. The new iMacs will downclock to any slower RAM speed. Retailers/manufacturers will update to add 21333 compatibility once they can test out the memory with the new iMacs themselves.
Some RAM brands may not work well with Macs than others. It is like a organ transplant recipient's body not accepting the organ perfectly.
I would say Crucial RAM has the best success with Mac systems judging by others and with my personal anecdotal experience. OWC second. Everything else a distant third (Corsair, HyperX, G.Skill).
As I said in the other thread:
'PC4-21333 and PC4-21300 are exactly the same thing. Some companies have simply chosen to round the value to three digits, while others took it out to five digits. (The "exact" number is 21333 and one third.)
A similar issue happened some years back with 1066 and 1866 MHz memory. The "exact" value there is xx66 and two thirds which some companies rounded up to xx67 while other truncated down to xx66.'
Well, this puts you at odds with the poster prior to you, who said 'they are slower (you won't notice) but are still supported'.
So now I don't know what to think!
curmudgeonette is right as well.
21300 technically doesn't exist so I was referring to official slower speeds like PC4-19200. Didn't mean to confuse you.
Take a look at a DRAM manufacturer's website, like: https://www.micron.com/products/dram/ddr4-sdram/part-catalog
Do you see them offering DDR4-2662.5 (i.e. 21300 / 8)? How about DDR4-2666.625(21333 / 8)? Nope, all they list in this range is DDR4-2666. If you were to blindly multiply this by the module width (8), you'd get PC4-21328 - but nobody sells anything like that.
All this confusion is because modern PC's clock rates are all referenced (frequency multiplied) to one third of 100 MHz, i.e. to 33 and one third MHz. For a while now, we've been advancing through multiples of eight times that 33 1/3 MHz, i.e. multiples of 266 2/3 MHz:
3 x 266 2/3 => DDR2-800 => PC2-6400
4 x 266 2/3 => DDR3-1066 => PC3-8500
5 x 266 2/3 => DDR3-1333 => PC3-10600
6 x 266 2/3 => DDR3-1600 => PC3-12800
7 x 266 2/3 => DDR3-1866 => PC3-14900
8 x 266 2/3 => DDR4-2133 => PC4-17000
9 x 266 2/3 => DDR4-2400 => PC4-19200
10 x 266 2/3 => DDR4-2666 => PC4-21300
11 x 266 2/3 => DDR4-2933 => PC4-23400
12 x 266 2/3 => DDR4-3200 => PC4-25600
Further, think about the accuracy needed to tell 21300 from 21333. CPU clocks are not that accurate. The 33 1/3 MHz is likely crystal referenced, but everything else is generated by a VCO in a PLL that compares to the 33 1/3 MHz. And it is quite likely that the 2666 2/3 MHz is VCO/PLL synced to a 266 2/3 MHz itself VCO/PLL synced to the 33 1/3 MHz. Further, in some systems, the 33 1/3 MHz is VCO/PLLed from 32768 KHz. (32768 KHz is mass produced as a very precise reference for digital watches!) All these VCOs/PLLs will wobble up and down slightly.
Quite alright...the replies forced me to look a bit harder myself and I came to the right conclusion in the end. Thanks for the explanations (you and curmudgeonette).
For the first time I'm going to use some Crucial RAM, the same that others here are using. CT2K16G4SFD8266. I usually get Kingston RAM (luckily never had any issues), but having issues finding it in Canada.
Yes, the specs are the same no matter what the RAM vendor.
So long as third party RAM matches those specs there should be no problems. I do recommend going with known quality brands like Crucial though.
Has anyone actually installed extra RAM. I have new i9 with 2x4GB from Apple. I have purchased 2x16 (the popular choice) for a total of 40GB. So far, I can't get it recognise the new RAM. I have done various slot swapping, so I know the Apple RAM works in either slots 2 & 4 or 1 & 3.
I have noticed that System Information has Memory Slots: EEC: Disabled, Upgradeable RAM: No. Should I be alarmed by the 'upgradable RAM: no'?
Any ideas how to make it work?
I have noticed that System Information has Memory Slots: EEC: Disabled, Upgradeable RAM: No. Should I be alarmed by the 'upgradable RAM: no'?
Any ideas how to make it work?
I got Corsair Vengeance Performance Memory Kit 32GB DDR4 2666MHz CL18 Unbuffered SODIMM. It recognized 40 Gb, but only at 2400. My theory is that the base 8Gb is CL19 and hence messing with speed. Now I have Crucial on order and hopefully try with that tomorrow.
Mine came with 4GB each in slot 1 and slot 3. I installed Crucial 16GB each in slot 2 and slot 4 before first boot. Everything is fine and it recognizes 40,960MB. https://smile.amazon.com/gp/product/B071H38422/
OWC already did. And I saw a Japanese tech site did it also. The hard part is to find a good deal with 32GB modules.
ok. thanks. I am receiving a new pair of crucial ram today to replace the Corsair ones. hopefully that will resolve the speed issue (2400 MHz instead of 2667 MHz).
Does anybody know the CL of the stock memory? I was planning on ordering these but seems like they might not be perfectly compatible...
https://www.amazon.com/Corsair-Veng...z+ddr4+sodimm&qid=1553893178&s=gateway&sr=8-3
I'm also ordering the base 27" though with SSD. I noticed the memory beyond 32GB wasn't selectable in the customizer, are there any memory limits when it comes to this model? I don't think I need more than 32GB anyway but just curious.
https://www.amazon.com/Corsair-Veng...z+ddr4+sodimm&qid=1553893178&s=gateway&sr=8-3
I'm also ordering the base 27" though with SSD. I noticed the memory beyond 32GB wasn't selectable in the customizer, are there any memory limits when it comes to this model? I don't think I need more than 32GB anyway but just curious.
Well, ”good deal”, I don’t know, but OWC charges 1100 USD for 128 GB, which is about half of what Apple charges for 64 GB.
This Corsair model was definitely incompatible with mine as it was lowering the speed to 2400 MHZ across all of my RAMs. I can confirm that the Crucial 32GB Kit (16GBx2) DDR4 2666 MT/s (PC4-21300) DR x8 SODIMM 260-Pin Memory - CT2K16G4SFD8266 is working fine for me.
For the UK folk here, this Crucial RAM on Amazon is correct for my new i9 IMac right?
https://www.amazon.co.uk/Crucial-CT...53255074&sr=1-25&refinements=p_4:Crucial&th=1
Would love confirmation - much appreciated!
https://www.amazon.co.uk/Crucial-CT...53255074&sr=1-25&refinements=p_4:Crucial&th=1
Would love confirmation - much appreciated!