Whats the Problem With 4+2=6gb RAM...

Generally memory is put in as pairs for dual channel memory and for the most part the lowest dimms you can buy are 2GB and generally they come in multiples of 2, so 2GB 4GB and 8GB.

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Simply put, it's best not to mix DRAM, period, even the same exact model, it can be problematic. DRAM is sold in a wide variety of packaged number of sticks and number of Gigabytes for a reason - it contains sticks that are tested to work together and if 1600 or better is loaded with the XMP settings for that particular amount of sticks and GBs. Tolerances are so tight on todays DRAM you can't with any certainty just grab 2 or 3 sticks off the production line and expect them to play nice - so they test them - and it's harder to find 4 sticks to play nice than it is two - which is why a 4 stick package of the same model of sticks may cost more than than two 2 stick packs

I've build MANY computers over the years and never once had an issue using RAM of the same model from different kits (tested with Memtest).

My own DDR3 2133MHz kit had FOUR sticks. One failed just recently so I sent in the pair and kept two, got the replacement pair and had no issues.

Do you know of any reliable statistics for problems with mixing memory of the SAME EXACT MODEL?

(G. Skill did recommend I send in the entire kit but then I'd have no PC for weeks.)

GSkill always recommends sending in the entire set, as do all other reputable DRAM makers, they also recommend against mixing set, as do the mobos makers... Think about it for a minute - if mixing DRAM was so easy and so sure to work - then

A) Why don't the DRAM makers just sell single sticks? (RMA's would skyrocket and are already high, and of sticks RMAed appr 85% have nothing wrong with them, they get RMAed as a result of folks mixing sets and also not knowing how to set up sticks that run faster than the mobo default - you've been around here for a long time and seen all the post asking why their DRAM isn't running at advertised freq, and you've had to have seen all the people writing in that they've mixed DRAM and it doesn't work

B) why does a 4 stick set cost more than a pair of 2 sticks sets? They test the sticks that goes into a package and it's much easier to find two sticks that will play nice, than it is to find 4 that play nice - then look at the 8GB sets and their prices....

C) The sticks are programmed by the packaged number of sticks for XMP, take a look in your BIOS sometime and see what the advanced timings are for a two stick set, say 2x8GB 2133 may take a 208 in the tRFC timing where a 4 stick set may take 278 (which is prob what yours takes if it's a 2133/9 set....

BIOS's are getting better and better, but for them to set up DRAM all they have is raw data from the SPD of the sticks - that's one of the reasons I often ask if a person has the latest BIOS, you seldom see it when you check for BIOS updates, they normally list 1 or 2 changes, but most every BIOS update is full of updates for adjusting DRAM

I'm glad you've had good luck mixing and hope it continues, but when you think about it (especially if you do systems for a living) is it worth trying to mix? Say they don't work off the bat (have you noticed the people here with problems going back and forth for a couple days or more - how many hours you think that involves ? - I value my time, and others should - they could be making money or having fun rather than being miserable), or if bought over the net, there's the time and expense of RMA, postage fees, time, maybe restocking fees and often a wait of a week (if you're lucky or more), or a return to a store and dealing with them, again time, frustration, maybe restocking fees and at some places they won't do anything.