Can I run with 2 sets of ram at different sizes/speeds/timings

Slayer697 · Mar 30, 2016

I'm currently running a set of 2x2GB 1333 7CL memory sticks in an ASUS P7P-55D Pro. Not sure on the manufacturer but I think GSKILL. I want to expand my memory after upgrading to windows 10 and was looking to buy a set of 2x4GB 1600 9CL memory sticks. I have, however, a few questions:

1. Will it matter that they're different sizes as long as they're both running in the correct channel pairs? My system should recognize this as 12GB correct?
2. Will the motherboard just downclock the faster memory pair to 1333 to ensure they're all at the same speed or will it do somethign else? I spoke to a representative at a store today but wanted to be sure before I made the purchase. I was only interested in the 1600 because it was cheaper than the 1333.
3. Does the timings being different matter at all?

As always, thank you for the help!

utroz · Mar 30, 2016

You most likely will be ok. You might have to manual set the ram speed in the bios, but it should automatically downclock to 1333Mhz and timings of your old sticks. I would put the new sticks in and see if the computer works properly, if it doesn't boot then remove the new sticks and manually set the ram speed to 1333Mhz. Chances are you 1333Mhz sticks might be able to be overclocked to 1600Mhz anyways, but all 1600Mhz sticks can run at 1333Mhz. The different sizes of the sicks should be fine as long as you have them in matched pairs in the same channel like you said.. The timings do matter some but usually newer sticks have lower (better, faster) timings so they can be relaxed to the timings of your old sticks if need be (same as running them at a slow speed 1333Mhz instead of 1600Mhz). I would try for 1333Mhz CL7 with all the memory installed, and then try upping to 1600Mhz CL9. If you are feeling really ambitious try running them all at 1600Mhz and lowering the CL timings (you might be able to get to CL8, CL7, or CL6). I would however test your system with Memtest http://www.memtest86.com/download.htm to make sure your system is stable with the new ram and with any overclocking you may do. You see memory makers sometimes sell ram that can run at faster speeds and timings because of demand for their slower cheaper parts (same thing that happens with CPUs) it is the silicon lottery.

ktolo · Mar 30, 2016

1. Usually no, but not necessarily. Not all ram is compatible with all motherboards. You should usually check your mobo's manufacturer's website for a RAM Comparability list.
2. Yes. That's usually exactly what happens. The 1333 ram will slow the 1600 down to 1333 - and it will all run at that speed.
3. Yes, but as you are mixing them, as above in 2. the timings from the 1333 will be in effect. The system cannot run two sets of timings for each channel.
Faster ram can run at tighter timings when running at slower speeds.

Slayer697 · Apr 2, 2016

utroz :

I went with the 8GB of ram and tried installing it in my machine. It's 2x4GB 1600Mhz CL9 and on it's own the system runs fine. When I try to add my old 2x2GB 1333Mhz CL7 ram, though, the system posts but windows freezes while loading. In the bios the settings tells me it's running everything at 1333Mhz CL9. As far as I could see there wasn't an option to change each individual stick's speed/timing. Why might I have trouble running all 12GB and not either of the pairs separately? I really hope it's something simple I would hate to have made the upgrade needlessly for a 6 year old system.

utroz · Apr 2, 2016

Have you tried different slots? Usually it is best to keep each pair on their own channel. Another idea is to try slightly more voltage for the ram and or IMC.

Slayer697 · Apr 2, 2016

utroz :

I did try different slots but always keeping them properly paired. In one case my computer didn't post and in the other it froze repeatedly while loading windows.

I was under the impression it would underclock the ram to the lower settings of the pairs. Is there something I misunderstood?

utroz · Apr 2, 2016

Yes it seems that it is automatically setting the clocks to 1333Mhz, but there are a million factors that can come into play when mixing ram. You could try manually setting the speed, voltage, and CL. You are not misunderstanding it is just hard to know 100% if mixing ram kits will work till you try it yourself. I am lucky that I have SPDTool so I can tell my RAM to be whatever I want (useful in OEM systems and Laptops that don't allow you to set memory speeds, voltages, and timings). I would like to see an CPU-z screen shot of each the ram kits complete specs. This might help me find out what is happening.

Slayer697 · Apr 2, 2016

utroz :

These are what I hope is all the relevant tabs out of cpuz. When I was running all 4 sticks together the 2x2gb sticks were in slots 2/4. Unless I've misunderstood something my ram should be running in dual channel with my current configuration so I don't understand why it's showing as single channel in cpuz. Any clarification is greatly appreciated.

EDIT

I'm including links to both sets of ram:
G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Desktop Memory Model F3-10666CL7D-4GBRH
G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBXL

Slayer697 · Apr 3, 2016

I updated my bios and now the system gets through to windows with all 12GB installed. On first boot I had windows crash when I tried to open Chrome so I went into the bios and set the voltage manually to 1.6V. So far I've been able to use windows without issues but I haven't really put it under any kind of stress yet (aside from opening about 40 tabs in chrome). Here's a snap of the cpuz memory tab:

Now that my system is working I still have some questions:

1. Why does cpuz report it running in single channel if each channel has the same amount of RAM?
2. Why did I need to up the voltage to get my RAM to stabilize? Each pair separately ran just fine at AUTO (which I believe was 1.55V) in the BIOS. Together they don't seem to want to work at a lower voltage.
3. Should I be concerned about upping the voltage to 1.6V from the rated value of 1.5V? Will this greatly increase the risk of the RAM modules failing?

Slayer697 · Apr 3, 2016

I may have a clue to why cpuz is showing me the ram is in single channel. When I look at my memory in the task manager it says I have 12GB but 6GB is hardware reserved. I've been trying to do some research on how to free up the ram for regular use but I can't find anything for Windows 10 64bit.

utroz · Apr 3, 2016

Ok I so I should have thought about the BIOS update, good idea. Also 1.6V isn't that much extra at all from 1.5V stock, so it shouldn't effect the life and the RAM at all. What you could do is download Memtest 86 http://www.memtest86.com/download.htm and it will test all your RAM to make sure it is stable. About the hardaware reseved issue try: Press Start -> Run, Type msconfig, Go under the "Boot" tab, Click "Advanced options" button, Uncheck "Maximum memory". About the single channel memory issue. Try putting the sticks in different slots, (if you have a matched set in slots 1+3 and other set in 2+3 try puttiing them in slots 1+2 and the other set in 3+4 or vice versa. I am hoping the BIOS update helps. Try this with the voltage set to 1.6V, the reason you might need 1.6V is that having all 4 slots filled with memory is a lot harder on the system especially with mixed ram sets..

Slayer697 · Jul 15, 2016

I thought I'd follow up on this since what ended up helping me might help someone else someday. I was able to get my ram running with 12GB but only after I did some more reading and eventually found a post where a user had a similar situation to mine and was able to resolve it by upping their IMC voltage. Unfortunately this was so long ago I don't have the link anymore, but sure enough upping my IMC voltage to 1.3V solved the problem for me. Recently I've noticed my computer sometimes and inconsistently restarts, but there's nothing to indicate that it's related to the ram or the IMC voltage increase. No BSOD. I've selected one of your answers utroz [strike]since you were most involved in trying to help me resolve this issue[/strike] since you actually mentioned that I might need to up the IMC voltage. Thank you to everyone for their help.

As an aside, I'm likely going to just buy another 8GB by the end of summer so I can have the full 16GB.

utroz · Jul 15, 2016

Glad to be of help. Yeah the extra load from 4 sticks of RAM on the IMC is probably why the IMC voltage increase helped.

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