When you run 2 sets of dual-channel memory, does it have to be the same speed?

[Boomax7299]

So I'm upgrading an old PC, it has 2 sticks of 2G of ram, I'm gonna get 2 more 2G sticks, does it have to be the same speed? Thanks! 

[Godlygamer23]

You should try to stick as closely as possible to the original kit that you got, but to answer your question, the speed listed doesn't matter because it's only the maximum supported speed. Most motherboards will default to the slowest stick in the system, which would include any new DIMM slots that have been populated.

[Boomax7299]

The PC is a prebuilt HP from a few years ago

[Damocles]

2 minutes ago, AnderZENZ said:

So I'm upgrading an old PC, it has 2 sticks of 2G of ram, I'm gonna get 2 more 2G sticks, does it have to be the same speed? Thanks! 

If it's the same DDR# then it should be fine. However, there's no guarantee though. I did something similar and the results you can expect is the speed of the higher RAM lowering to the lowest RAM speed of the set. Timings and command rate will auto adjust and may lower performance. But at least you'd have more GBs of RAM

[Godlygamer23]

3 minutes ago, Damocles said:

Timings and command rate will auto adjust and may lower performance. But at least you'd have more GBs of RAM

Performance for the "faster" DIMMs will naturally be less, but performance won't drop - it'll either be the same, or higher than previously.

[Damocles]

2 minutes ago, Godlygamer23 said:

Performance for the "faster" DIMMs will naturally be less, but performance won't drop - it'll either be the same, or higher than previously.

This doesn't make sense, unless you think more GBs to be proportional to performance. I tried to install 1066 with 1333 ddr3s in an old Acer prebuilt and I got 1066 running in 1 command rate per transfer. It is slower and technically no longer double data rate 3, more like single data rate 3 or SDR3

[Godlygamer23]

4 minutes ago, Damocles said:

This doesn't make sense, unless you think more GBs to be proportional to performance. I tried to install 1066 with 1333 ddr3s in an old Acer prebuilt and I got 1066 running in 1 command rate per transfer. It is slower and technically no longer double data rate 3, more like single data rate 3 or SDR3

What I said was that the performance will not decrease for the system unless you're deliberately adjusting speeds, or putting in slower DIMMs than before. In this user's case, the DIMMs are advertised to run at a higher speed than what they are going to be, which would mean he's keeping the old DIMMs in the build, and therefore performance will not decrease for the system - it will either stay the same, or increase. Dual channel allows for two DIMMs to be accessed at the same time, which would give double the bandwidth theoretically.

[Damocles]

2 minutes ago, Godlygamer23 said:

What I said was that the performance will not decrease for the system unless you're deliberately adjusting speeds, or putting in slower DIMMs than before. In this user's case, the DIMMs are advertised to run at a higher speed than what they are going to be, which would mean he's keeping the old DIMMs in the build, and therefore performance will not decrease for the system - it will either stay the same, or increase. Dual channel allows for two DIMMs to be accessed at the same time, which would give double the bandwidth theoretically.

I guess you don't understand what I'm saying. You're right for starters. I'm only saying it's possible for memory timings and command rate to auto adjust like mine does in order coexist.

[Boomax7299]

You've lost me  Oh well, I think I've gotten the answer I wanted, thanks!