Old RAM chestnut: 2 modules versus 4

[Biggsy]

I can find lots on this from Googling, but half of it's written by people who I'm not convinced know what they're talking about, and half of it is some years old.  (I suspect 2008 is ancient history as far as this sort of thing goes).

On an Asus P7P55D-E motherboard with an i7 CPU, with a 64-bit OS, will two sticks of 4 GB RAM run quicker than four sticks of 2 GB, assuming all else is equal?  Could there be a lot less heat as well?  Assume budget isn't an issue (though it might be really).

The BIOS can do some clever auto overclocking, which I employ to some extent.  The RAM I have at the moment is rated at 2000 MHz, but is more typically set to around 1500, or 1333 MHz with default settings.  Fank you very much.

[tiermat]

No, you have it the wrong way around.

If you have the right motherboard (i.e. one that supports it) and the right RAM (ditto) then 4 sticks of identically specced RAM will run fast than 2, irrespective of size.

The reason? You get wider data paths, so more of your pron junk data is thrown at the memory in one go.  Useful up to a point, if you are only ever processing data that is smaller than a data chunk in this scenario then there is no gain( and possibly some loss), but if you are processing large video files (or databases) then it is faster.

[Kim]

I'm a bit out of touch with what's current in the PC hardware world, but I don't think there's a basis for a performance difference, other than some flavours of RAM supporting magic overclocky stuff I don't really understand which don't like more than one stick per channel.

ETA: I'll defer to tiermat on that one.  I wondered if that was the case.


In heat terms, I suspect that 2G and 4G DIMMs will run at about the same temperature.  Only having two of them may improve air circulation.

All else being equal, I'd always go for the larger sticks.  More upgrade potential later on.

[Biggsy]

Most of the stuff I Googled (amateur posts in computer forums) say two sticks are faster because it's less work for the CPU, or something.  Is this bollocks?

[tiermat]

Yes, complete and utter petite bolleaux, as our cheese eating surrender monkey friends are unlikely to say.

Common misconception, grasped by those that have no idea what they are on about but sounds plausible enough to be repeated ad nauseum across the internet until it reaches a point where it must be true.

Cynical about people with a little knowledge of IT^[1], me?^[2] Nah...

[1]Otherwise known as empty vessels....
[2]I am not inferring that anyone on here fits into this category, before anyone goes off on one

[Biggsy]

I'm liking what you say, Tiermat, because it suits what I've actually done!: bought two more sticks of 2 GB instead of replacing what I've got with two 4 GB.  The stuff I read was making me doubt myself and delaying me opening the packet of new goodies that arrived today.  (I was wondering about returning them instead).  Thanks.

[fuaran]

If the motherboard supported quad-channel memory, then using 4 separate sticks should be a bit faster.
Checking the specifications for that Asus motherboard, it says it only supports dual-channel, so this won't apply. Note that you may need matching sticks in each channel, for dual channel to work.

In terms of power consumption, it seems to be something like 5W or 10W per stick, so it will mean a bit more heat. Though this may vary depending on just what type of memory it is.

[Feanor]

Splitting the memory between multiple sticks can usually allow the motherboard chipset to do dual-channel 'interleaving', ie alternalte addresses live on alternate sticks.

This is slightly faster, because it can start an access cycle to the incrementally next address ( which is on t'other stick ) before the previous cycle has completed.
So slightly concurrent memory access cycles.
Marginally faster than sequential accesses on one stick.

No CPU hit as this is handled in hardware on the motherboard chipset.

[Tigerbiten]

All things being equal 4 sticks should run as fast as 2.
But some bios's with underclock 4 sticks slightly versis the speed of 2 sticks.
That way your less likely to get memory errors.
But I don't think you'll notice the difference.

[Biggsy]

Splitting the memory between multiple sticks can usually allow the motherboard chipset to do dual-channel 'interleaving', ie alternalte addresses live on alternate sticks.

I know dual-channel is faster than single-channel, but as fuaran says, this motherboard doesn't do true quad-channel, it's just two lots of dual-channel.

[Wombat]

I'm liking what you say, Tiermat, because it suits what I've actually done!: bought two more sticks of 2 GB instead of replacing what I've got with two 4 GB.  The stuff I read was making me doubt myself and delaying me opening the packet of new goodies that arrived today.  (I was wondering about returning them instead).  Thanks.

I've added to the original 2x 2Gb sticks in my identical motherboard, with 2x4Gb sticks of identical spec (but from another manufacturer)  Dunno if its the perfect answer, but it seems to have helped!

[Valiant]

4 sticks should run cooler due to having more surface area for heat dissipation. But that does depend on whether it's more efficient to power another stick or drive a few more chips.