Different Memory Modules - 2020 5K iMac

[Newfiebill]

Hi Everyone, I have a new 2020 5K iMac and I upgraded the stock 8GB (2x4GB) to 16GB (2x8GB) sticks. Can you have a look and tell me if I have them installed properly please? I have included a picture of my memory set up. I am not sure if I should do it as I have done or if it should be installed differently. Thanks!

 

[wilberforce]

There is a long thread on upgrading RAM in the 2020 iMac (because it has some quirks different from any other Mac), but I will give you the shortened version:
Yes, you have installed them correctly, because you have the same amount in Channel A as in Channel B, which enables full dual channel operation which is the most important thing.

However, notice that the speed has dropped from the normal 2667 MHz to 2133 MHz. This, unfortunately, is the quirk of the 2020 iMac which is: if the Part Number in slot 1 does not match exactly the Part Number in slot 2, or the Part Number in slot 3 does not match exactly the Part Number in slot 4, the speed will drop to 2133 MHz.

You can use it like this, but realize your memory speed is slightly lower than optimum. (Results in maybe 5% decrease in overall computer speed).

If you want to have full memory speed, you really only have two options:

• Use four sticks the same size, with matching part numbers in slots 1/2 and 3/4.
• Use two sticks the same size, one in each Channel, and discard the 2x4GB Apple sticks

IMO, the most cost effective solution to get full memory speed is 2x16GB sticks and discard the Apple sticks.

To reiterate: whatever you do, the most important thing is that the total GB in Channel A is the same as in Channel B. If not, the mismatched portion will run in single channel mode, which is effectively half the transfer speed.

 

[Newfiebill]

There is a long thread on upgrading RAM in the 2020 iMac (because it has some quirks different from any other Mac), but I will give you the shortened version:
Yes, you have installed them correctly, because you have the same amount in Channel A as in Channel B, which enables full dual channel operation which is the most important thing.

However, notice that the speed has dropped from the normal 2667 MHz to 2133 MHz. This, unfortunately, is the quirk of the 2020 iMac which is: if the Part Number in slot 1 does not match exactly the Part Number in slot 2, or the Part Number in slot 3 does not match exactly the Part Number in slot 4, the speed will drop to 2133 MHz.

You can use it like this, but realize your memory speed is slightly lower than optimum. (Results in maybe 5% decrease in overall computer speed).

If you want to have full memory speed, you really only have two options:

• Use four sticks the same size, with matching part numbers in slots 1/2 and 3/4.
• Use two sticks the same size, one in each Channel, and discard the 2x4GB Apple sticks

IMO, the most cost effective solution to get full memory speed is 2x16GB sticks and discard the Apple sticks.

To reiterate: whatever you do, the most important thing is that the total GB in Channel A is the same as in Channel B. If not, the mismatched portion will run in single channel mode, which is effectively half the transfer speed.

Thank you. Excellent information indeed.

 

[Grubster]

Hi Everyone, I have a new 2020 5K iMac and I upgraded the stock 8GB (2x4GB) to 16GB (2x8GB) sticks. Can you have a look and tell me if I have them installed properly please? I have included a picture of my memory set up. I am not sure if I should do it as I have done or if it should be installed differently. Thanks!View attachment 2182453

I just upgraded mine to 32 gb yesterday using owc 16x2 kit. It was 10 bucks off on Amazon, $68 and 1 day shipping. I removed the Apple stock RAM to get full speed, 2666mhz.

 

[Dannydematio]

Do you always have to ditch the Apple factory installed Ram when you want to upgrade the 2020 iMac 27? or can you keep the 8 gig and add say 2x OWC modules in the two remaining slots. It's a bit confusing if you can mix the ram modules, which slots to use or if it will cause the machine to slow down or not? actually forget that, I just woke up and scrolled up and got the explanation thanks anyway

 

[Grubster]

Do you always have to ditch the Apple factory installed Ram when you want to upgrade the 2020 iMac 27? or can you keep the 8 gig and add say 2x OWC modules in the two remaining slots. It's a bit confusing if you can mix the ram modules, which slots to use or if it will cause the machine to slow down or not? actually forget that, I just woke up and scrolled up and got the explanation thanks anyway

I installed mine and kept the 8GB initially, but it did register at a slower speed…. You PROBABLY, won’t even notice the slow down, but I think it makes sense to just pull them! For me the machine runs flawless with 32 gb of ram, so not sure what 40 would even buy me! If unsure, just spring for the 64gb up front.