It is better to have the same speed ram, but typically you can get different speed ram to work without crashing/etc by placing the slower one in the first slot (eg marked as slot 0). Also you can often set the ram speed in the bios to the slower speed to avoid issues.  Faster ram will work at lower speeds but not the other way around. Ram is cheap though so often it's better to just by the fastest and biggest ram you can afford.
JD

On Thu, Sep 15, 2022 at 11:17 AM Michael Butash via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
It will usually figure out some level of compatibility that it *will* work, until you start getting weird segfaults or crashes for no apparent reason.  My new used laptop came with mismatched 2x2 16gb sticks and *worked*, but not something I want to test with 128gb of ram going into it when I tend to actually use it.

I've dealt with it a few times in my life that it's worth some expense to avoid all that with matched sticks.

-mb



On Thu, Sep 15, 2022 at 11:08 AM Stephen Partington via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
Some laptops and NUC's are single channel or will default to that if they cannot match for dual channel compatibility.

On Thu, Sep 15, 2022 at 2:07 PM Michael via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
interesting. well, I must be one-lucky-dog then! I mis-matched an 8GB and a 4GB with no ill effects.

On Wed, Sep 14, 2022 at 6:01 PM Michael Butash via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
I would highly recommend NOT mixing and matching sticks of ram, this has never ended well for me, particularly since most everything is dual-channel configs these days and really need to be paired exactly per bank.  If you do/must, match them up as close as possible in terms of speed, cas/ras latency, etc, or only use the exact same ram down to the model number. 

I've long ago stopped mixing and matching sticks of ram for weird pc crashes, I always put them in as a set now.  Matched sets by batch are best, or if needing a bunch of sticks for a server, buying a batch of same sticks used of ebay out of the same server has been good to me too, just make sure to run a memtest on them first to make sure they're good if used. 

Likewise test if using off brand random sticks, they're probably cheap for a reason ie. 2nd rate parts.  These days I only use samsung memory.

-mb



On Wed, Sep 14, 2022 at 2:34 PM Michael via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
Thanks for the tip!

On Wed, Sep 14, 2022 at 4:34 PM Stephen Partington <cryptworks@gmail.com> wrote:
if your motherboard/bios is well designed yes, they will run at the slower speed. you can even encourage this compatibility by installing the slower module in the first memory channel.

On Wed, Sep 14, 2022 at 4:32 PM Michael <bmike1@gmail.com> wrote:
Thanks! Does that mean both will be the slower speed?

On Wed, Sep 14, 2022 at 3:31 PM Stephen Partington <cryptworks@gmail.com> wrote:
technically yes. but one is faster than the other.

On Wed, Sep 14, 2022 at 1:57 PM Michael via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:
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Stephen



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