Laptop RAM "upgrade" question

[Relativitus]

Quote

So I scavenged some old 4gb probably DDR3 memory from an old laptop and was thinking... if I put it in the expansion slot of my ROG Zephyrus gaming laptop with a single stick of DDR4 16gb memory, even though its just 4gb, the fact that it becomes dual channel, would it make the 16gb more efficient/effective or just purely add more memory? Would it even somehow make the 16gb less effective? I'm still learning and would really love an answer and would super appreciate an explanation with it if possible.

 

[Needfuldoer]

DDR4 and DDR3 are not cross-compatible. If it's DDR3, it won't work in your laptop.

 

If it's DDR4 it should work, but all your RAM would run at the speed of the slowest DIMM. You'd be better off running one fast 16 gig DIMM by itself than adding a slow 4 gig DIMM to it. (Mismatched DIMMs aren't ideal anyway.)

[Kilrah]

You can't put DDR3 in a DDR4 machine.

[Eigenvektor]

43 minutes ago, Relativitus said:

DDR4 16gb memory, even though its just 4gb, the fact that it becomes dual channel, would it make the 16gb more efficient/effective or just purely add more memory?

Compatibility issues mentioned by the others aside, if you combine 16 GB and 4 GB, then only 4 out of the 16 GB will run in dual channel with the other 4 GB stick and the remaining 12 GB are still single channel. So you would only gain performance for some of your RAM and only if the additional stick doesn't have slower speed forcing the other stick to drop down. But as was mentioned you can't mix DDR3 and 4 anyway.

[Relativitus]

11 hours ago, Needfuldoer said:

DDR4 and DDR3 are not cross-compatible. If it's DDR3, it won't work in your laptop.

 

If it's DDR4 it should work, but all your RAM would run at the speed of the slowest DIMM. You'd be better off running one fast 16 gig DIMM by itself than adding a slow 4 gig DIMM to it. (Mismatched DIMMs aren't ideal anyway.)

@Eigenvektor @NeedfuldoerGot it. Thanks. I feel a little dumb for not knowing the DDR* compatibility thing but hey, that's what learnings for.