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What RAM to buy to update new iMac launched today?
- Thread starter spinstorm
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I don't know of any way to confirm that RAM is running in dual channel mode in MacOS via software. If you have BootCamp you can use CPU-Z.
In MacOS, if you have matching DIMMS in matching banks then dual channel is automatically enabled. In About This Mac > Memory, the matching banks are represented horizontally:
The top row is DIMM0 (Bank 1 and Bank 2) and the bottom row is DIMM1 (Bank 1 and Bank 2). In the memory compartment at the back of the machine, however, the matching banks are alternating slots.
This information is also available under Memory in System Report.
thank you very much.
this morning I was able to place my ram correctly as stated above.
I did a geek bench (after a reboot)
I was roughly 5358 / 16754
which is fine.
but after doing the ram "right" this morning. I rebooted and got
5763 / 19928
so.
it matters.
I installed a 16 GB Crucial kit from Amazon: https://smile.amazon.com/gp/product/B01BIWMWVS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
It's not listed as compatible with the 2017 iMac, but the specs are identical to the approved kit. The only difference is it doesn't say halogen free or lead free.
When I installed the modules into the available two slots, I didn't hear a click when pushed in all the way. (The Apple instructions mentioned a click.) The modules are in as far as I can get them, and they're level with the top of the Apple-installed RAM. The iMac shows a total of 24 GB and the RAM seems to be working perfectly.
It's not listed as compatible with the 2017 iMac, but the specs are identical to the approved kit. The only difference is it doesn't say halogen free or lead free.
When I installed the modules into the available two slots, I didn't hear a click when pushed in all the way. (The Apple instructions mentioned a click.) The modules are in as far as I can get them, and they're level with the top of the Apple-installed RAM. The iMac shows a total of 24 GB and the RAM seems to be working perfectly.
I didn't really here a click either. they are seated well. expected more of a click though
Once again, I am not being lazy or rude with mentioning it. I've seen the few threads it's mentioned, but people still have not gone into details on why it's cheaper then OWC and Crucial for that matter.
Absolutely! Clearly we are using the same exact RAM because my Geekbench results are nearly identical.
5737 / 19923
I doubt very much that it makes a difference but I was going to trying swapping the Ballistix into DIMM0. Did you end up with the Crucial in DIMM0 or the Apple stock RAM?
Please do a swap!
and if it isn't too much work please post the results for (only) 32 GB aftermarket RAMs.
I'm really curious about this.
I will give it a try and post my results.
I was also curious actually about whether or not and how badly the Apple stock RAM is slowing things down.
I'm going your route and getting the same RAM. After reading your advice about Crucial, this looks excellent indeed.
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I'm going to play around with it when I have a moment just to see if rearranging makes a difference.
I think you'll be pleased with it.
I just ran memtest on 64 GB of the non-Mac Crucial RAM for six hours, no errors.
This was after one my Memtest sessions with the Crucial Ballistix of over 3 and a half hours in extreme ambient temps.
Not sure how accurate the bandwidth reading in Memtest86 is as it seems to be rather variable. My results are similar to ArcticMoose's.
I'm still planning to swap the slots as well as temporarily remove the stock RAM for benchmarking to see what, if any effect it has.
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In System Report > Memory, DIMM0 is the top two boxes, DIMM1 the bottom.
I'm using the crucial 16gbx2 (CT2K16G4SFD824A) and the stock 8gb ram. Slightly slower memory bandwidth.
But what is confusing to me is why are there differences in my Clk and L1-L3 cache. Mostly these are small but the L2 score is much lower on my i7 (90B/s vs 120 GB/s).
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How are you running Memtest86? Is it off a boot flash drive?
Have you tried rebooting and running again and do the cache speeds change at all?
I'm running memtest off of a boot usb flash drive.
I just tried a number of reboots. Maybe around ~10. All except one were at the normal rating of 119GB/s for L2 cache. One time I got 104 GB/s. Forgot to take a picture for this one.
I have no idea what's going on. I guess it could be (1) a bug in memtest or something interfering with bandwidth measurement, (2) variable L2 cache bandwidth is normal for cpu, or (3) something is wrong with my cpu.
I just tried a number of reboots. Maybe around ~10. All except one were at the normal rating of 119GB/s for L2 cache. One time I got 104 GB/s. Forgot to take a picture for this one.
I have no idea what's going on. I guess it could be (1) a bug in memtest or something interfering with bandwidth measurement, (2) variable L2 cache bandwidth is normal for cpu, or (3) something is wrong with my cpu.
This is what I suspected. I think the problem here is definitely Memtest86 and I wouldn't worry about it too much. I was getting vary variable bandwidth numbers as well.
Well that's good to know. I remember you made a comment earlier about variable numbers, but didn't realize you meant this order of magnitude.
Yes, the first time I ran it I got about 19.00GB/s for memory bandwidth. After that it was back to normal.
I downloaded memtest86 and transferred it to a usb flash drive. But the mac doesn't see it, when I reboot and press the option key to bring up the drive selection menu, I don't see that menu...it just goes to the apple logo and the mac boots as normal. What am I doing wrong? This is frustrating.
EDIT: had to plug magic keyboard into USB in order for option key to be noticed. Running tests now.
EDIT: had to plug magic keyboard into USB in order for option key to be noticed. Running tests now.
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Did you just copy it to the flash drive? You have to follow the instructions in the Readme file to format and write the image. I edited the text below slightly to make it more understandable by using the actual image file's name.
Launch the Terminal app.
Code:
1) Insert a USB drive into a USB slot.
2) Determine which device the USB drive is assigned as by opening the Terminal and typing the following command:
diskutil list
3) Unmount all volumes on the USB drive by typing the following command:
diskutil unmountDisk [device name]
4) As root, use the 'dd' command to write the image to the USB drive. For example,
sudo dd if=memtest86-usb.img of=<dev>
where <dev> is the device the USB key is assigned to. Use the base device (ie. /dev/disk1) not a partition designation (ie. /dev/disk1s1).
Warning: all data on the USB key will be lost.
Warning Warning: Make sure that the device used in the dd command above
is correct!!!Thanks. It was literally that the startup manager wouldn't come up because of the wireless keyboard. Memtest is running now.