[QUOTE=petrw1;438455]To clarify does that mean that both sticks are on the same side of the memory bank instead of 1 on each side?[/QUOTE]

If both memory channels don't have the same amount of memory, then the memory access can't be interleaved between the two channels.

[QUOTE=Mark Rose;438462]If both memory channels don't have the same amount of memory, then the memory access can't be interleaved between the two channels.[/QUOTE]

What if he has 2 - 4's in 1 bank and 1 - 4 in the other?
Is he best to simply remove one of the pair of 4's?

Could I have 2-4'x on 1 side and an 8 on the other?
Do all the sticks have to have the same specs?
...I mean for interleaving to be supported and work effectively?

I can't say for certain, but I'd only put them in slots like this:

4 4 x x
8 8 x x
8 8 4 4

OR

4 x 4 x
8 x 8 x
8 4 8 4

It depends on your motherboard, if slots 1 and 2 or 1 and 3 are part of the same channel. You'll have to check the manual.

Channels are frequently color-coded on the RAM slots.

weirdness. double post. I didn't think the above had gone through.

If the computer / mother board came with DDR3 can I replace it with DDR4?
I notice they have different Pin Counts

If it helps it is this OEM PC:

Acer Aspire T3 Gaming PC (Intel Ci7-6700)

[QUOTE=petrw1;438490]If the computer / mother board came with DDR3 can I replace it with DDR4?
I notice they have different Pin Counts

If it helps it is this OEM PC:

Acer Aspire T3 Gaming PC (Intel Ci7-6700)[/QUOTE]

hi,
no, you can not replace the ddr3-dimms with ddr4-dimms
(exeption: some mainboards have both slots but they are usually not good)

And finally I assume they also must be same speed?
 

To interleave that is.

Or if I find the current 8GB stick is 1600 and I add a 2133 8Gb stick will it still interleave and get full dual-channel memory sharing?

Probably, but they'll both run at 1600, so you're wasting your money on faster RAM.

[QUOTE=petrw1;438924]To interleave that is.

Or if I find the current 8GB stick is 1600 and I add a 2133 8Gb stick will it still interleave and get full dual-channel memory sharing?[/QUOTE]

He opened the box and found the RAM was DDR3 833 (is that even possible nowadays)

Anyway if the benchmark gave him 7.68 ms for 2048 FFT on 1 core (equivalent to other similar CPUs); actual speeds of 16ms for all 4 cores concurrent; can I expect it to be a lot faster, that is I'm thinking 2400 or even 2133 DDR3 may be overkill; more than I need

Thoughts....

[QUOTE=petrw1;439101]found the RAM was DDR3 833 (is that even possible nowadays)[/QUOTE]No?
I believe the spec starts at 800 and goes up in 266 increments (800, 1066, 1333, 1600, 1866, 2133, 2400, etc).