[SOLVED] Can I use 2x1gb ram in one channel and 2x8gb in the other without throttling capacity?

[Budgeteer_262]

Hi,

Looking on the internet has not given a definitive answer so I might as-well ask directly:

If I have a motherboard with 2x1gb sticks installed in one channel, and then I add 2x8gb in the other channel, will the 8gb modules only be able to use 1gb of their respective capacity?

In other words, would the result perform like a 4gb ram system or like an 18gb system?

From what I garner, if you put an 8gb module alongside a 4gb module in the same channel, the 8gb module capacity will only be utilised as much as its partner 4gb module. If this is true, I'd like to know if this also applies to having different size modules in different channels, with all the modules in their respective channels being of the same size.

Please assume that the module frequencies, cas latency and timings are the same.

Thanks in advance!

 

[DSzymborski]

They'll be able to use the full RAM, but only if it works. There's a very good chance it just doesn't work at all with such grossly mismatched sticks or, if it works, it cripples the performance.

I can't imagine, however, a scenario in which the trouble and the jankiness makes going from 8 GB to 10 GB of RAM worthwhile.

 

[Bob.B]

Hi,

Looking on the internet has not given a definitive answer so I might as-well ask directly:

If I have a motherboard with 2x1gb sticks installed in one channel, and then I add 2x8gb in the other channel, will the 8gb modules only be able to use 1gb of their respective capacity?

In other words, would the result perform like a 4gb ram system or like an 18gb system?

From what I garner, if you put an 8gb module alongside a 4gb module in the same channel, the 8gb module capacity will only be utilised as much as its partner 4gb module. If this is true, I'd like to know if this also applies to having different size modules in different channels, with all the modules in their respective channels being of the same size.

Please assume that the module frequencies, cas latency and timings are the same.

Thanks in advance!

Start with just the 2x8GB sticks.
Fit them in the proper slots for dual channel.....see the manual.
Verify all the ram is seen and dual channel is enabled.
Test for a while to make sure of no problems.

If all ok fit the other 2 sticks in the mobo and see what happens.

 

[USAFRet]

You're looking at 16GB vs 18GB.
Just leave the 2x 1GB out of it. They wouldn't add any actual performance.
And may reduce performance, if it even worked at all.

 

[Budgeteer_262]

Thanks, I will try both when by 8gb modules arrive to complement/replace my 1gb modules.

 

[Karadjgne]

It's called flex mode, been around for years. What'll happen is the first 1Gb of the 8Gb sticks will see dual channel with the 1Gb sticks, but the remaining 7Gb will be in single channel.

Since you'll have 4 sticks, nothing will change there, you'd still be in dual channel, 2 x1 and 2 x8, but what will happen is a severe increase in the probability of instability, since you'd be not only mixing ram kits, but those kits will have seriously different timings which will give the memory controller fits, and most likely gimp any attempted performance gains from the additional ram.

Best advice, keep the 2 x8Gb, and literally throw the 2 x1Gb in the trash can.

 

[Budgeteer_262]

Just to clarify, is flex mode only activated because the 8gb and 1gb modules would have different timings, or would flex mode be enabled even if the 1gb modules had the same timings as the 8gb modules?

Thanks

 

[Karadjgne]

There's 3 modes. Single channel, dual channel and flex. In single channel, ram stick size doesn't matter, it just adds up. In dual channel, size must be equal as that's a hard physical limitation, speeds can vary, as can timings as they'll adjust to an equitable level. Flex mode happens when you have different size ram in dual channel, where the larger ram size will match and link to the smaller, in dual channel, with the remainder being used last, in single channel.

Mainstream boards are single/dual channel capable, so with 4x sticks, you get 2 sets of dual channel, which is dual channel.

With 2x sticks, you'd have 1Gb x2 in dual channel, with remaining 7Gb in single channel. But with 4x sticks, that remaining 7Gb is in dual channel with the other 7Gb.

So while technically in flex mode, all the ram runs in dual channel, while not strictly being in dual channel mode.