imac 2010 21.5" i7 max ram?

[kwikdeth]

Perhaps some folks may be able to help me out with this unusual question.
I have a thing for upgrading old Macs. Any kind. Just to see what they were like if they got completely maxed out.
I was recently given a 21.5" 2010 i3 iMac for free, with a busted video card.
Ive already set out on using the guides on this forum to upgrading that to a WX4150 card. I've got a Samsung 850 Pro SSD for it.

Now when it comes to the RAM, I am getting a LOT of conflicting information as to what this machine is capable of having as its maximum RAM.
While the machine is currently an i3-540, I have an i7-860S (low power) on the way which I have confirmed through many posts does indeed work. Its my understanding that in the 27", it can be upgraded to 32GB RAM. But many sources say 16GB is the maximum for the 21". I've also found some posts saying some people have gotten these to see 24GB RAM when upgraded with an i5 or i7.

I had come to the conclusion that 16GB was a hard limit due to there only being 2 RAM slots... But now I'm getting confused in the fact that when I opened this thing up I found it had four total RAM slots. I'm not used to seeing that in a 21" iMac... every other smaller iMac I've worked on has been a 2-slot machine. So what happens to the existing RAM if I put another 16GB in? Is it just not recognized past 16GB? Where does the 24GB come from, and if that's true, does it require a special config, such as 8 x 8 x 4 x 4, or could you use 3x 8GB modules? Is 32GB completely out of the question? Or is it a case that its so obscure that nobody's tried it?

I know its an ancient machine and what I'm doing is moderately obscure, but I'm really curious to see how well it will perform with the upgraded CPU and new video card. Right now though, I'm trying to figure out how much RAM I need to order for it.

I appreciate any info people can offer on this matter.

 

[Bigwaff]

16GB Memory Upgrade Kit For Apple iMac 2010-2011

Enhance the performance of your 2010-2011 Apple iMac with a 16GB memory upgrade kit from OWC. Save money by trading in your original memory chips.

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i3 max is 16GB.

 

[B S Magnet]

Perhaps some folks may be able to help me out with this unusual question.
I have a thing for upgrading old Macs. Any kind. Just to see what they were like if they got completely maxed out.
I was recently given a 21.5" 2010 i3 iMac for free, with a busted video card.
Ive already set out on using the guides on this forum to upgrading that to a WX4150 card. I've got a Samsung 850 Pro SSD for it.

Now when it comes to the RAM, I am getting a LOT of conflicting information as to what this machine is capable of having as its maximum RAM.
While the machine is currently an i3-540, I have an i7-860S (low power) on the way which I have confirmed through many posts does indeed work. Its my understanding that in the 27", it can be upgraded to 32GB RAM. But many sources say 16GB is the maximum for the 21". I've also found some posts saying some people have gotten these to see 24GB RAM when upgraded with an i5 or i7.

Due to the density of the RAM modules on DDR3, most of the pre-Haswell Macs are limited to 16GB per channel because of chip design constraints. Specifically, an 8GB stick will have sixteen, 500MB (same as 4 Gigabit) modules from one of maybe three or four manufacturers; the CPU/chipset for pre-Haswell cannot handle module densities greater than 500MB — thus, 500x16 x 2 == 16 GB (and now that I’m thinking about it, it might even be Broadwell, which didn’t really emerge until 2014). Typically, a channel can have up to two slots for RAM, which is what shows up on many Intel Macs between 2006 and 2013.

The smaller display iMacs, such as the 2012–2014 A1418, were designed with two RAM slots on one RAM channel. This was a question which came up not too long ago on the Early Intel Macs forum, and which was answered with pretty good clarity by folks far more knowledgeable than I’ll ever be (the whole thread is worth a good read).

I had come to the conclusion that 16GB was a hard limit due to there only being 2 RAM slots... But now I'm getting confused in the fact that when I opened this thing up I found it had four total RAM slots. I'm not used to seeing that in a 21" iMac... every other smaller iMac I've worked on has been a 2-slot machine. So what happens to the existing RAM if I put another 16GB in? Is it just not recognized past 16GB? Where does the 24GB come from, and if that's true, does it require a special config, such as 8 x 8 x 4 x 4, or could you use 3x 8GB modules? Is 32GB completely out of the question? Or is it a case that its so obscure that nobody's tried it?

If your A1311 has four slots (this is news to me!), then it’s a safe deduction that there are two RAM channels. This ought to permit 32GB. At the very minimum, you could test this theory by throwing in 2 x 8GB sticks (which would max out two slots anyway) and whatever else you have lying around in the other two slots: if you have two memory channels on the A1311, running an i7 CPU, then you should be able to see north of 16GB in System Information (and the system ought to POST and boot without trouble).

I know its an ancient machine and what I'm doing is moderately obscure, but I'm really curious to see how well it will perform with the upgraded CPU and new video card. Right now though, I'm trying to figure out how much RAM I need to order for it.

Nah. Neither obscure nor ancient. I’ve nominated your question to be moved over to the more relevant forum, the Early Intel Macs forum, where a community of folks using older Macs maintain these with upgrades and updated, even patched OSes. These older Intel Macs still have a surprising amount of kick built into them, even in 2023.

 

[kwikdeth]

Nah. Neither obscure nor ancient. I’ve nominated your question to be moved over to the more relevant forum, the Early Intel Macs forum, where a community of folks using older Macs maintain these with upgrades and updated, even patched OSes. These older Intel Macs still have a surprising amount of kick built into them, even in 2023.

Thanks for your reply and also for moving it to the correct forum. I didnt realize there was one specifically for the older intel imacs. Ive got an i7-860S on the way from China so I will have a chance to experiment with this and see what kind of results can be expected. I did order 16gb RAM, I figured in the end, RAM is so cheap right now who cares if I have to order a second set... but you make an interesting point with the RAM density and its got me wondering if there's any 8GB sticks out there that use lower capacity chips. If there are, they are probably early 8gb sticks and pretty exotic. Also ordered a new wifi card + adapter as I'd like to attempt using OCLP on this to get it as upgraded as possible. Pretty excited about messing with this once I get all the parts! Ive been doing Hackintoshes for ages so I've got lots of patience for experimentation.

 

[kwikdeth]

well I can now confirm, a 2010 21.5" iMac, once upgraded with an i7-860s processor, can indeed see 32GB of RAM!
woohoo!
Well, next up is OCLP installation, then the WX4150 I picked up for this.

 

[kwikdeth]

Well, a further update to my iMac story...
After the successful CPU and RAM upgrade, I set about replacing the GPU, HD with an SSD, a wifi and bluetooth card, and upgrading it to Monterey.
For the most part the OS upgrade was pretty easy using OCLP. I got the upgrade installed and running perfectly with the old original GPU, but after I did the upgrade to WX4150 GPU, I did run into a hiccup where TG Pro tried to open up on startup before I had a chance to customize it to the new GPU, this would cause a crash every time. Target disk mode wouldnt work for some reason and I ended up having to remove the drive, connect it to another machine, and remove all the TG Pro components. After this, the iMac would boot normally and I was able to customize it for the new WX4150. After that, TG Pro was reinstalled and has worked fine ever since.
I got a brand new WX4150 from a US seller off ebay. They are rev 1.1 hardware (made in 02-2023) and do not have the temperature ICs or the resistors that need to be bridged like earlier cards. Also, I did not have to install a copper shim as when fitted everything made good contact. Ive been using it for a few days now and the GPU hasnt gone over 120F during that time.
I had this old thing laying around called a "IceDrive" which was basically a huge heatsink for western digital's 2.5" 15,000RPM hard drives in a 3.5 form factor. I thought that perhaps if I used one of these with the SSD, it might pass temperature data through to the machine, as the IceDrive has the 8-pin connector the HD temperature sensor connects to. Sadly, it turns out SSDs just dont pass temp data that way so I had to make due with TG Pro's SMART monitoring to run the HD bay fan.
I used a wifi adapter with a USB breakout so I could patch into the existing BT USB dataline. Additionally, I bought some internal wifi antenna extension cables, and was able to just route it to where the existing internal BT antenna ended and connected it there.
Its been working great. There's a few processor related things where the machine shows some age, but for the most part it runs just as good as anything else. This isnt my daily driver machine, more a "when im in that room" kind of machine, and for that purpose its going to work great.

Thanks to all the great people and resources here on MR without which I wouldnt have even dreamt of being able to do something like this.