Aniky

Populating memory slots by itself won't prohibit you from reaching a certain overclock. What may impact the stability is the voltage droop and/or tolerances.

As to why differing brands with similar specs not running well...

Each manufacturer fine tunes their chips for their specific configurations, think of it as a fingerprint.  Also, most RAM is sold in matched sets (pairs, triples, etc) that were tuned/produced at the same time/same batch.

This isnt an absolute, but its like mixing oil and water; They are tuned slightly different

Welllllll.....


Depending on the make of your motherboard, there are various types of memory controllers. This translates down to the component level and some of those components regulate voltage.

Lots of manufacturers use non-oil filled capacitors...That is, those little, flat circle looking thingies that stick up. These are cheap to produce and use, but they are averse to heat and they break down faster (relatively speaking). In addition to the capacitors (usually a couple of them, one in "front" of the regulator and one "behind" it) you have a POT (variable resistor) and one or more other resistors. A resistor by it's nature generates heat.

Looking at the motherboard, these components are very small, but when dealing with electron flow on a micro scale, it only takes fractions of a degree to throw things off.

This was a valid reason in years past (im talking 10+) because as you added more DIMM's, you required more power and generated more heat and taxed those poor little voltage regulator constructs.

In todays' world of computers,  especially in triple channel configurations, if you dont fill all three banks you actually get degraded performance because the memory cant interleave. In a nutshell, interleaving is error-correction.

You would be truly amazed at how error prone the secret inner-workings of our computers are. On a micro-scale, there is sooo much interference and interesting little quirks (magnetic destabilization, electron propogation, etc) that transmissions are actually pretty prone to error, especially as you ramp up the voltage to increase "speed".

As to which banks to "fill". This will depend entirely on the manufacturer and the "type" of memory. A sort of standard was adopted that you would fill alternating pairs of banks of memory (0&2, 1&3, etc), but some manufacturers do not adhere to that. Consult your owners manual for your hardware to be sure.


As to the sizing of ram in the various banks, generally, the reason you can't populate a paired memory bank with different sized memory is due to the addressing scheme.

If bank 0 has 1 gig of ram and its' pair, bank 2 has 512megs, when the system goes to write to it and it gets to the point where it is writing out past the 512meg mark, it will have a page failure because the error-correction bit will be missing and it will go crazy trying to figure it out (or used to hehe).

In most modern schemes, putting two 1 gig modules in a paired configuration results in 1 gig of total memory. It addresses them as a unit, in a non-additive way, and uses them in a manner that provides a high degree of error correction, thus attaining the speed they operate at.

The "speed" of memory is not just about how "wide" or how hard you pump the transmission, but how error-free it is. If 50% of a 3ghz memory transmission is full of errors, it will only appear to be 1.5ghz (actually less due to overhead, etc).

Aniky, on 03 April 2010 - 06:09 PM, said:

Triple channel does only apply to DDR3 modules.