DIMM slots 3 & 4 not recognized.

[Motown_Johnny]

I upgraded my RAM from 4 x 2 gig to 4 x 8 gig but DIMM slots 3&4 are not recognized. They are all exactly the same chips (NEMIX RAM DDR3 1600 Desktop Memory Module - MD12800 - 828LK04-517) and all 4 slots were working before I upgraded. I have run basic memory tests, including the on in BIOS and everything passes. I have also removed and reinstalled the chips to insure they were installed properly. The problem still exists. Is there some way to resolve this issue? 

[BeemerBiker]

You may need to reset the CMOS.  I think it can be done using the Windows key and the "V" key as described in item 2 below

https://support.hp.com/us-en/drivers/selfservice/swdetails/hp-compaq-elite-8300-small-form-factor-pc...

Do not do a bios reset.  However, I did look here and read the bios release and did not see a mention of a problem with missing memory.  The most recent bios is 3.08 but possibly the problem is memory compatibility

I guess that your product ID is A2K82ET and looked at a parts list.  If your product ID is different then change the following

https://partsurfer.hp.com/partsurfer/?searchtext=A2K82ET&searchby=product

The recommended 8gb memory modules are HP part number 689375-001

That memory is double sided and should be is 2Rx8 (double rank)  If the memory you bought is single sided (high density) then it may not be compatible.

Please download CPU-z and look for the rank of the memory you are using

Should look something like my HP Pro-3400

You can also test your old memory and check its  rank.

[Motown_Johnny]

Thank you for responding so quickly.

I have to assume that the memory modules are not the problem since all 4 are identical and 2 of them work fine. Also, I may be confused but I believe my Product ID is D1W67US#ABA

[BeemerBiker]

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@Motown_Johnny wrote:

Thank you for responding so quickly.

I have to assume that the memory modules are not the problem since all 4 are identical and 2 of them work fine. Also, I may be confused but I believe my Product ID is D1W67US#ABA

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Thank for for providing the Product ID

Your parts list is here

https://partsurfer.hp.com/partsurfer?searchtext=D1W67US

The recommended HP memory is part number 689375-001 the same as my previous guess

Please look at your new memory.  It is has chips on both sides it should work.  Does it say 2Rx8 or 1Rx8 on label

If 2Rx8 then you may have a bad slot.  Use one stick and test all 4 slots.

Possibly a BIOS upgrade will allow high density to work.  I did not see any reference to memory in any of the BIOS upgrades and I do not recommend a BIOS upgrade.

Did you  run CPUz to confirm the ram is organized with the same rank as the old ram?

Reset the CMOS?