DIMM Question

[Bino]

Is there any measurable advantage to having all the DIMM slots in a motherboard populated?

I'm curious to know if "interleaved" memory access is of any tangible value.

Thanks! 

[gyrene81]

The short version is...depends on the hardware architecture of your mobo...i.e. chipset...memory version...dual channel...triple channel...etc.

[MrRiplEy[H]]

Is there any measurable advantage to having all the DIMM slots in a motherboard populated?

I'm curious to know if "interleaved" memory access is of any tangible value.

Thanks! 

Sometimes there's a measurable disadvantage to have all the DIMM slots populated as some motherboards can't really cope with them. Also the more DIMM's you have inserted the better they need to match eachothers or stability will start to suffer. Usually the safest compromise is to populate two DIMM's with the largest possible combs to get the wanted amount of ram. Two because you'll want dual channel (or triple channel with three combs on i7). Safest compatability wise would be to use a single large stick but then you'd be stuck to single channel operation.

[Bino]

OK, good comments.  And I'm familiar with the stability issues.  Can those be dealt with by using top-shelf components?  Assuming that stability can be achieved, what then? 

I'm thinking about this in the context of a new machine: X58/ICH10R chipset, DDR3 triple-channel RAM, big honking PSU, etc.

[Spikes]

OK, good comments.  And I'm familiar with the stability issues.  Can those be dealt with by using top-shelf components?  Assuming that stability can be achieved, what then? 

I'm thinking about this in the context of a new machine: X58/ICH10R chipset, DDR3 triple-channel RAM, big honking PSU, etc.

Well, you may not need a huge PSU depending on what you're doing...if you're getting a i7 with 1 GFX card, you probably won't need much more than a 600W PSU or so...but I see the X58 offers triple SLI...do you plan on getting three graphics cards? might want to look into a nice big one or even two smaller ones (depending on the case) then. Not that triple SLI is necessary, but.

[Ghastly]

It depends.  In the context of what seems like is the question you are actually trying to ask - if the CPU you are installing is triple channel (i.e. i7), and the motherboard has 3 slots total, use 3 DIMMS, at least IMO.   

However, I've seen some benchmarking that suggests that that's not actually the case - that dual channel is actually just fine and that the performance gains are minimal.  http://www.tweaktown.com/articles/1665/intel_core_i7_memory_analysis_can_dual_channel_cut_it/index7.html

I'm skeptical though, especially as performance means nothing without stability - and you can be sure that no one is really focusing on ensuring the stability of a dual channel implementation of a core that's designed for triple channel.

Give us specifics on which motherboard and processor and you'll get a more exact answer - or a better set of conflicting opinions, most likely!

<S>

[Bino]

Well, I was hoping to avoid specifics because I'm curious to know if there is a general observation that can be made about interleaved memory.  Guess not.

I am planning a new machine around an X58/ICH10R mobo (Asus P6T) and an i7-920 CPU, with triple-channel DDR3 RAM (Corsair Dominator) and a big enough PSU to eliminate that as a source of gremlins (OCZ Z850 single-rail).  The specific makes and models are not yet definite.

Thanks!  

[Ghastly]

Yes, there is a general observation that's rudimentary enough that I suspect people aren't quite sure what you are asking. Single channel memory (i.e. non-interleaved) will "starve" a modern processors  - it cannot provide sufficient bandwidth for memory intensive operations.  Single versus Dual-Channel  is an absolute no-brainer with today's processors.

What's less certain is whether you "really need" Triple-Channel, or if you can get away with Dual-Channel without significantly degrading performance. 

Is that what you were looking for?

<S>

[Bino]

Sorry, guess I must not have been clear. How about this:

Recent triple-channel motherboards typically have six DIMM slots.  These are usually shown with RAM mounted in only three of those six DIMM slots.  Assuming that any RAM stability issues can be dealt with one way or another, is there any advantage to having all six DIMM slots populated?

[Ghastly]

Ahhh. 

To my knowledge, no.  No motherboard that I'm aware of does anything "different" with six DIMMS versus having only three installed, such that (excluding the obvious increased capacity) there is no advantage to filling all six versus only 3 - assuming the DIMMs all have identical timings. Which brings us to the one caveat - often smaller DIMMs have tighter timings, such that you can get a bit of increased performance from more smaller DIMMs versus fewer larger ones for the same total RAM - a fact that is usually offset (or even overwhelmed) by the fact that the more DIMMs you have installed, the greater the likelihood of stability issues.

<S>

[Bino]

Thanks very much for the input! 

I suppose I've just been lucky, then.  I have not had issues with RAM stability, either at home or at work.