All RAM sticks only recognised after clearing CMOS and not on subsequent boots

Soldato
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*EDIT* Making some progress. If I change the RAM frequency to be 2000Mhz all of the RAM is recognised. Would like to see if I can get it all recognized at the right frequency though. *EDIT*

Got a weird issue. I have an unRaid server which had 16GB RAM and wanted to upgrade to 32GB. I bought some new (used) sticks on eBay which match what I already have.

For reference this is the hardware:

Mobo: ASUS X99-WS/IPMI
CPU: i7-5820K
RAM: HyperX Fury 2400Mhz DDR4 (8GB DIMMs x 4)

I have checked the manual and I am confident I have installed the DIMMS in the right slots (there is 8 in total I am using A1, B1, C1, D1.

When I first installed everything the BIOS was only seeing 16GB. I swapped the RAM in the slots (so the old ones were swapped with the new ones). It was still only seeing 16GB.

I updated the BIOS to the latest version, still only seeing 16GB.

Tried fiddling with lots of BIOS settings, still only seeing 16GB.

Removed some of my PCI-E devices, still only seeing 16GB.

Finally I tried removing the CMOS Battery. After the machine rebooted it could see 32GB. However whenever I reboot the machine after that (without changing any settings) it goes back to 16GB again! Agh!

Interestingly on the boot after a CMOS clear XMP settings aren't available in the BIOS. After I reboot they are available. I've tried setting everything the same between the first CMOS boot and subsequent reboots and haven't had any luck.

Tried sending some more voltage to the RAM (1.35, 1.4, 1.5) doesn't seem to help.

There is a 'tool' in the ASUS Bios called ASUS SPD Information. It can see that there is something in the slots I have the DIMM installed however, on two of them it doesn't have any 'Module Size' or 'Maximum Bandwidth' information.

Any ideas why it might not be working?

Here are some photos of the BIOS post booting after clearing CMOS:

https://imgur.com/gallery/uGCrudB
 
Last edited:
Soldato
OP
Joined
18 Oct 2002
Posts
2,912
Location
London
The sticks aren't from a kit so they may well not be a perfect match.

The build dates are week 12 of 2016 and week 49 of 2017 so a fair amount of time between them.

You can see the details of the RAM here in the BIOS:

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Associate
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6 Dec 2007
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Location
Cambridge
OK sounds like classic mismatched sticks. They'll be fine at lower speeds but not at xmp speeds. I'd look for a 4 stick kit, or buy 2 kits grim the same retailer. Should maximise your chances of a match.
 
Soldato
OP
Joined
18 Oct 2002
Posts
2,912
Location
London
OK sounds like classic mismatched sticks. They'll be fine at lower speeds but not at xmp speeds. I'd look for a 4 stick kit, or buy 2 kits grim the same retailer. Should maximise your chances of a match.

Yeah, probably. They are all running fine together at 2000Mhz. The performance difference will be minimal so happy just to leave it like that for now. Won't try and mix and match in the future and just buy kits for what I want/need to rule out any of this.

Have you tried in dual channel rather than quad channel ?

Yeah everything worked fine in dual channel.
 
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