Question Mixing identical Corsair RAM Kits

[PC Hoarder]

I saw a pair of Corsair Dominator Platinum RGB 3200 DDR 4 (2 x 8GB) on Amazon quite affordable and bought it. However, I want to make full use of 4 slots of ram and went to get the same kit with the same specs and model. Instead of buying (4 x 8GB), I went with 2 kits of (2 x 8GB) to save about 100 bucks. Some people say that mixing ram kits even though they are identical may lead to instability and perhaps unable to operate smoothly in DOCP mode. Have I made the mistake of saving $100 to get two kits instead? It hasn't arrived at my home yet and cancellation of my order has been declined as it is already been shipped.

 

[Zerk2012]

I saw a pair of Corsair Dominator Platinum RGB 3200 DDR 4 (2 x 8GB) on Amazon quite affordable and bought it. However, I want to make full use of 4 slots of ram and went to get the same kit with the same specs and model. Instead of buying (4 x 8GB), I went with 2 kits of (2 x 8GB) to save about 100 bucks. Some people say that mixing ram kits even though they are identical may lead to instability and perhaps unable to operate smoothly in DOCP mode. Is it true? It hasn't arrived at my home yet and cancellation of my order has been declined as it is already been shipped.

No answer because it might work and might not work.
Could even be made with different parts.

Edit since your saying DOCP then your using a Asus board with a AMD processors making it less likely to work.

 

[geofelt]

Ram is sold in kits for a reason.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
The internal workings are designed for the capacity of the kit.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards, particularly ryzen, can be very sensitive to this.
This is more difficult when more sticks are involved.
Ram must be matched for proper operation.

Be prepared to specify all of the ram settings yourself in the bios as well as specifying higher than normal voltage for the ram.
That (may) get you working.
Test the result.
Run memtest86 or memtest86+
They boot from a usb stick and do not use windows.
You can download them here:

MemTest86 - Official Site of the x86 Memory Testing Tool

MemTest86 is the original self booting memory testing software for x86 and ARM computers. Supporting both BIOS and UEFI, with options to boot from USB.

www.memtest86.com

Memtest86+ | The Open-Source Memory Testing Tool

Memtest86+ is an advanced, free, open-source, stand-alone memory tester for 32- and 64-bit computers (UEFI & BIOS supported)

www.memtest.org

If you can run a full pass with NO errors, your ram should be ok.

Running several more passes will sometimes uncover an issue, but it takes more time.
Probably not worth it unless you really suspect a ram issue.

 

[Misgar]

I'm running two different 2x8GB kits with the same part number on a 3800X for 32GB total but I had to reduce the DOCP overclock from 3200 to 3000MHz. Hardly a surprise when you consider the extra bus capacitance and the unmatched pairs.

Fit all 4 DIMMs, don't be too enthusiastic with XMP and run some stress tests. You might be lucky.

 

[PC Hoarder]

Ram is sold in kits for a reason.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
The internal workings are designed for the capacity of the kit.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards, particularly ryzen, can be very sensitive to this.
This is more difficult when more sticks are involved.
Ram must be matched for proper operation.

Be prepared to specify all of the ram settings yourself in the bios as well as specifying higher than normal voltage for the ram.
That (may) get you working.
Test the result.
Run memtest86 or memtest86+
They boot from a usb stick and do not use windows.
You can download them here:

MemTest86 - Official Site of the x86 Memory Testing Tool

MemTest86 is the original self booting memory testing software for x86 and ARM computers. Supporting both BIOS and UEFI, with options to boot from USB.

www.memtest86.com

Memtest86+ | The Open-Source Memory Testing Tool

Memtest86+ is an advanced, free, open-source, stand-alone memory tester for 32- and 64-bit computers (UEFI & BIOS supported)

www.memtest.org

If you can run a full pass with NO errors, your ram should be ok.

Running several more passes will sometimes uncover an issue, but it takes more time.
Probably not worth it unless you really suspect a ram issue.

I'll play around with the sequence and stress test it with OCCT. Hope I'm lucky otherwise I'll just return it to Amazon.

 

[Misgar]

Some programs benefit far more from additional RAM than from enthusiastic XMP overclocking.

If you can get away with a slightly lower XMP or DOCP setting, then your saving of $100 will be "justified".

 

[Nighthawk117]

I saw a pair of Corsair Dominator Platinum RGB 3200 DDR 4 (2 x 8GB) on Amazon quite affordable and bought it. However, I want to make full use of 4 slots of ram and went to get the same kit with the same specs and model. Instead of buying (4 x 8GB), I went with 2 kits of (2 x 8GB) to save about 100 bucks. Some people say that mixing ram kits even though they are identical may lead to instability and perhaps unable to operate smoothly in DOCP mode. Have I made the mistake of saving $100 to get two kits instead? It hasn't arrived at my home yet and cancellation of my order has been declined as it is already been shipped.

In an ideal world you would buy the entire kit together, however I've done exactly as you suggest and never had a problem. If your on Intel I would say with some confidence you won't have an issue. 4 dimms put's more stress on the memory controller, it's common on Ryzen to have to lower the speed to compensate. However you can still encounter this issue with a kit, for example Zen 2 will run 2 sticks at 3600Mhz but may not necessarily run 4. Zen and Zen + are more limited in the speeds they can support with 4 dimms.

 

[DSzymborski]

It will likely work, but not certainly. It's also good to move on from the idea that there's such a thing as identical RAM. All RAM is different; RAM that is sold together is RAM that was found to be defective to a similar degree, so specced and then tested together. It's not a binned product; they're not cranking out specific MHz RAM in a factory somewhere as part of the same brand.

CPUs are the same way. On a fundamental level, a 5600X, a 5800X, and a 5900X are just 5950X chips that are defective to different degrees (or made so as part of market segmentation).

 

[PC Hoarder]

It totally works even in DOCP mode. Stress tested for several hours and switched the order around without issues. Seems that luck is on my side this time.

 

[Misgar]

Excellent news.

You could use Thaiphoon Burner to check which manufacturers' chips are on the two pairs of DIMMs. If you're lucky, they might be the same (but obviously not from the same batch).

Have you checked the Primary and Secondary timings of the two pairs (in SPD) to see if they're identical or merely similar?

When I've mixed dissimilar DDR3 RAM, the BIOS sometimes picks a few timings out of one SPD and other timings out of a second SPD. These were experiments on non-critical systems.

 

[PC Hoarder]

Excellent news.

You could use Thaiphoon Burner to check which manufacturers' chips are on the two pairs of DIMMs. If you're lucky, they might be the same (but obviously not from the same batch).

Have you checked the Primary and Secondary timings of the two pairs (in SPD) to see if they're identical or merely similar?

When I've mixed dissimilar DDR3 RAM, the BIOS sometimes picks a few timings out of one SPD and other timings out of a second SPD. These were experiments on non-critical systems.

Everything is identical. Mine is made by Samsung.