Z87-G45 Memory Placement

[scole of TSBT]

I just added 2x 4GB 1600Mhz DIMMs to a system that had 2x 4GB 1333Mhz DIMMs in it and it didn't blink. It just downclocked all to 1333Mhz automatically. Maybe a difference in BIOS?

[leecarver]

Just a quick update: I left the 2x8s in the system and enabled XMP in the MSI BIOS. No problems so far, no unexpected shutdowns. I did some digging on Tom's and posted my question there and the only response I got back was that it wouldn't work and to just leave in the 2x8s.

However, I'm still optimistic they should work together - I just don't want to damage anything in the process. I've found an article that walks through the process of manually downclocking (http://www.overclock3d.net/articles/mem ... _voltage/1). It seems like I'll need to pull the 2x8s out, put back in the 2x4s, downclock them, and then reinsert the 2x8s.

Scole - curious, how were you able to do it automatically? What BIOS/Board are you using?

[scole of TSBT]

mobo is a MSI Z77A-GD65 https://us.msi.com/Motherboard/Z77AGD65 ... o-overview

It had 2x 4GB 1333Mhz DIMMS already. I didn't change anything. I just popped the 2x 4GB 1600Mhz DIMMS in the other 2 slots and it booted right up and has run without any problems. I didn't realize it had te 1333Mhz DIMMS in it already either. That's why I bought the 1600Mhz DIMMs. After it booted up I started checking things and noticed it reported the memory speed as 1333Mhz, checked and realized what had happened. Guess I got lucky.

[leecarver]

Interesting.

I'm wondering if because XMP is on and the 2x8s are now running at 1600Mhz (theoretically) if I pop the 2x4s in, if it'll run without a problem.

Guess this will be a week of trial and errors.

[leecarver]

Interesting.

I'm wondering if because XMP is on and the 2x8s are now running at 1600Mhz (theoretically) if I pop the 2x4s in, if it'll run without a problem.

Guess this will be a week of trial and errors.

[leecarver]

Another update: After running the 2x8s stable for quite some time, I put the 2x4s into the system on Sunday. The system booted up just fine, so I shut it down, went into BIOS and enabled XMP again. Rebooted and the system was still running as intended. Let it run all night with BOINC going in the background and it's still going strong.

I'm not a huge fan of the heatsink/memory placement right now, but I haven't seen much change in the temperatures (running in the low 30Cs when not under load, averaging around 55-56C while running two instances of POGS and 1 instance of GPUGrid). I think I'll try running this until it goes unstable. If it refuses to boot again, I'll just pull the 2x4s and go with the 16GB.

Thanks for all the input!

[scole of TSBT]

What does CPU-Z report the frequency of each DIMM as, under the SPD tab?

[leecarver]

I'm not sure which frequency to give you as there are four of them listed for each slot (JEDEC #4 / JEDEC #5 / JEDEC #6 / XMP-1600).

Slot #1 (4GB): 685 / 761 / 800 / 800
Slot #2 (8GB): 609 / 666 / 666 / 800
Slot #3 (4GB): 685 / 761 / 800 / 800
Slot #4 (8GB): 609 / 666 / 666 / 800

[scole of TSBT]

Not sure SPD was the right tab for info now. How about the DRAM frequency under the memory tab?

[leecarver]

DRAM Frequency fluctuates between 799.9 and 800.1 MHz.

[scole of TSBT]

Looks like it's all running at 1600Mhz then.

In case anyone was curious why it's reported at 800Mhz instead of 1600Mhz, like me, this is from tomshardware.com....

"DDR" means Double Data Rate".

CPU-Z reports the raw DRAM frequency x 2 = effective data rate.

What you're seeing is simply a difference in nomenclature.

"DRAM Frequency" in CPU-Z means one thing; "DRAM Frequency" in your BIOS means TWICE that!

If you were viewing the memory clock as a sine wave, you would have 1 peak and 1 trough for every cycle: that's how DDR works: it transmits data once for each rise in voltage and once again for every drop in voltage.

Of course, the sine wave analogy is "analog" --whereas DRAM is digital -- more like a "step function" as opposed to a smooth undulating "wave".

Because CPU-Z has become a de facto standard, get used to the tables produced with the "Memory" and "SPD" tabs in that fine program.

[leecarver]

Thanks for the reply, scole! I'm going to keep my fingers cross these two will play nice with each other going forward.

And am certainly glad to have CPU-Z as a new tool to understand and utilize.