Oh dear lord...so much confusion.
When you stop and look at the setup, it makes sense.
Bank and Channel are intermixable terms...they both refer to one grouping of memory accessible in parallel with the right setup.
DIMM refers exactly to what it says...the DIMM itself (or the chip or the slot), which is the physical piece of hardware.
Bank 0/dimm0 - First Channel, First RAM Chip
Bank 1/dimm0 - Second Channel, First RAM Chip
Bank 0/dimm1 - First Channel, Second RAM Chip
Bank 1/dimm1 - Second Channel, Second RAM Chip
This is how it's ALWAYS been setup on motherboards in the last several years since Dual Channel (and now Tripple Channel) operation was first introduced. Every motherboard interleaves channels slot to slot. If the first slot on the motherboard is channel 0 the second slot is ALWAYS channel 1. If your board runs dual channel memory, then you typically have 4 or 8 slots for memory and it will run channel: 0, 1, 0, 1 (for 4 slots) or 0, 1, 0, 1, 0, 1, 0, 1 (For 8 Slots). If your board supports tripple channel memory (Hello Apple welcome to 2010) then you typically have 6 or 12 DIMM slots on the board and they run the following channel layout: 0, 1, 2, 0, 1, 2 (for 6) or 0, 1, 2, 0, 1, 2, 0, 1, 2 (for 12).
As such, what Gogol is posting is absolutely correct. It's 8, 4, 8, 4 or 4, 8, 4, 8 as the correct config, NOT 8, 8, 4, 4 or 4, 4, 8, 8 which would produce a single channel setup. Crucial recommends the 8, 4, 8, 4 configuration (confrmed by Apple according to earlier posts in the thread) because it allows the larger of the two sets of dual channeled memory to be accessed first...limiting any potential cross manufacturer issues till you get beyond 16G of memory used.
To maximize your performance put MATCHING DIMMs into DIMM0 and DIMM1 (or DIMM0, 1 and 2) of a given "Bank" (Channel). DIMMS in Channel 0 and Channel 1/2 do NOT need to match or even be of the same size, so long as DIMM0 and DIMM1 (And DIMM2 for tripple channel) of each channel are identical.
HOWEVER every DIMM in ANY SLOT in ANY CHANNEL must be the same type (DDR3, failing this it won't work at all and will probably destroy the RAM chips and maybe the slots), speed of DIMM (PC3-12800/DDR3-1600), and CAS Latency (CL=11). Changing any of these causes the ENTIRE MEMORY LAYOUT to support only the SLOWEST speed available. (Placing a single PC3-10800 DIMM into a set of 8 slots all the rest filled with PC3-12800 RAM will cause the PC to work at PC3-10800 speed).
Many people will tell you that putting the same TYPE (manufacturer, brand, etc.) of RAM in all channels increases speeds or stability. That may be the case and it certainly won't hurt. But so long as you're using high quality RAM keeping the manufacturers the same shouldn't be an issue.
Another "Best Practice" is to purchase the RAM "Kits" from a given high quality manufacturer instead of seperate RAM chips. KITS are specifically put together by the manufacturers from the same "run" of the same chips. By installing "Kits" (the 2x4 or 2x8 you see sold on sites like Crucial or Corsair) you are not only guaranteeing the same chips, you're also guaranteeing the same COMPONENTS on those chips and the same conditions under which those chips where produced. When you go to, say, Crucial and buy two separate 8G Ram Chips, you are not guaranteed to get two RAM chips from the same run. One chip may be signficantly older than the other (wear issues), one chip may have different internal compoents (capactors, resistors, even the silicon for the board may be different), or even one of the two chips may have been manufactured in different plants under VASTLY different conditions. Buying "Kitted" RAM (supposedly) removes these kinds of potential differences.
The second major misunderstanding I've seen posted on this thread is summed up well by the following:
"Come on think for a second... The basis for dual channel memory is 2 memory channels that can be simultaneously accessed by the CPU therefore doubling the throughput."
Sir, I don't think you quite understand what dual channel RAM actually means. No offense intended, but your understanding seems flawed by what I'm reading from you.
Dual Channel does not mean that the RAM ACROSS CHANNELS is accessed in parallel, it means that the ram WITHIN THE SAME CHANNEL is accessed in parallel.
Your suggestion to make sure to keep the RAM in both channels the same leads me to believe that you feel that 12G in Channel 0 and 12G in Channel 1 would allow the PC to Dual Channel 12G of memory. This is incorrect and a flawed understanding (again, no offence intended). Only the RAM within a given channel can be accessed in parallel, thus the 2x4 in a Channel and 2x8 in another Channel is the right configuration, not 8+4 in Channel 0 and 8+4 in Channel 1.
--Illydth
