TripleChannelRAM | Dual Channel Mobo | Performance Issues

[commissarmo]

Ok - I have 6 sticks of (formerly expensive) triple channel (Corsair Dominator) RAM from another machine. But I want to use it in a new build which will use a Core i5 CPU - hence the triple channel won't work (and I don't want to buy either a Core i7 OR a triple channel mobo).

I know I can run the RAM on a dual-channel motherboard without incident. But what I'm not sure about is what type of performance penalty I'd have? I believe that if I use 4/6 RAM sticks, I should be able to achieve dual channel mode, if I understand correctly?

I also intended to overclock this machine.

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While I would like to use the RAM since its unused, would I be better off simply buying new RAM? I'm worried that my Corsair RAM is now useless as it was only designed for a very niche system (X58, Core i7, triple channel)...

Any advice out there?

 

[jaquith]

First, there's no such a thing as 'Dual/Tri/Quad' channel RAM, the RAM's SPD/XMP is optimized for it's intended use. Since the advent of an IMC there's very little difference in higher frequency and lower CAS timings so the penalty if any are what Frequency and CAS Timings you can manually get away with setting. In most instances if you can get the RAM to run at DDR3-1600 CAS 9-9-9-24-2N then you'll lose nothing.

However, the problem with older DDR3 beyond DDR3-1333 quite often requires 1.60v~1.65v with higher than 'good' DRAM Voltage and often same with the VCCIO (VCCSA) and/or CPU VTT voltages so they remain stable. The Dominator series has very good IC's and most are very good to run beyond 'Rated' speed.

Q - What exact Dominator's?

 

[commissarmo]

Dominator GT 2000MHz 1.65v 8-8-8-24.

What would happen then if I ran all 6 modules on a Dual Channel Motherboard?

 

[jaquith]

Dual channel MOBO's only have 4xDIMM slots so you'd have 4x2GB (8GB), and the new fixed BCLK on the Sandy or Ivy Bridge CPU's offer either DDR3-1866 or DDR3-2133. I assume you had two kits of CMG6GX3M3A2000C8.

Therefore chances are you'd have 8GB running at DDR3-1866 CAS 8 with excessive DRAM voltage and VCCIO (VCCSA) and/or CPU VTT voltages.

So will they work sure, are they ideal for the CPU no. Ideally, on SB/IB I recommend 4x4GB CAS 9 @ 1.50v or even DDR3L @ 1.35v.

Memory has gotten better, faster and cheaper and now you can purchase a 4x4GB DDR3-2133 e.g. CMT16GX3M4X2133C9 for $230 but similar kits sell as low as $99 with effectively no difference in performance.