RAM differences... iMac 5k i7 2017

[Hallstar]

I have recently acquired a 2017 iMac 27" 5k with a 4.2 GHz i7 processor and (currently) 24 GB RAM.

I am looking to put another 16 GB RAM into the machine, but am getting confused of options available and am keen to get some guidance..

Crucial system lookup (scan only returns an error!) indicates DDR4 PC 2400 MHz SO-DIMM CL17 (Part no: CT16G4S24AM) and is listed as 'for MAC'.

Amazon UK lists the same specification RAM (Crucial) for £15.00 less than the Crucial website, but with a different part no: CT16G4SFD824A Amazon link
Crucial link

The technical specifications as listed on Crucial website for both part numbers are identical.

Any suggestions on why there are independent offerings?

Will the NOT 'for MAC' be ok for my iMac?

 

[wilberforce]

I have seen various vague claims that the “for MAC“ versions have higher level of testing, or quality control, or marketing, or more green, or better warranty, or make you feel better, or whatever.
But really it just needs to meet the spec given here:

Install memory in an iMac - Apple Support

Get memory specifications and learn how to install memory in iMac computers.

support.apple.com

Crucial is a respected brand. Many people have successfully used RAM which is not marked “for MAC.”
Occasionally RAM from any brand is dud, so just buy from somewhere with free returns.
btw, however you add or replace ram, make sure the amount of ram in channels A and B is the same, else you lose full dual channel operation and speed

 

[joevt]

I usually just go to https://eshop.macsales.com/upgrades/ , choose my Mac, then pick how much RAM I want.

If the iMac supports PC19200 DDR4 2400MHz SO-DIMMs, then it may also support faster PC21300 DDR4 2666MHz SO-DIMMs (but use them at the slower speed).

 

[mreg376]

I also vote for OWC/Macsales.com for Mac RAM. They know the machines, know what you need, and I have never had a problem with their RAM. In fact, I have 64GB of OWC RAM in my 2017 iMac i7 (same machine as yours) running for almost 5 years.

 

[wilberforce]

I think OP is in UK, so OWC may not be the cheapest option.
Crucial (aka Micron) is considered by many to be the top brand for RAM.
btw, OWC RAM has had issues in some 2020 iMacs, so do not have a perfect record, but do have good customer service.

 

[Hallstar]

Thanks for the responses, all.

As per the specs listed in my OP, I now have two modules of the ‘for Mac’ and two of the standard modules.

All modules are Crucial.

What is the best configuration to install them as?

‘For Mac’ in slots 1 & 3

Standard in slots 2 & 4