Jeez, good questions. I kind of cringed at trying to answer these... It's been a while since I've studied the low-level stuff for RAM, but I'll see if I can help clarify a bit.
Reading around, it seems that 'banks' is used in similar but subtly different ways:
Yeah, us techs do like to re-use our lingo.
1) as a group of sockets or modules that make up one logical unit, with the logical unit referring to a match between the processor's data bus width and the RAM's bit width e.g. one 64-bit DIMM or two 32-bit DIMMs makes a full bank with a CPU with a 64 bit data bus.
Makes sense, this term of banks refers to how modules are organized on the mobo. Most motherboards have two or three DIMMs per bank, and generally 2 banks per board.
2) but then other people refer to banks of memory addresses, or as banks of "switches" in a RAM chip (each switch being 1 transistor/capacitor set)
This actually deals with how a memory module works on the inside. Generally speaking, in the old days most RAM modules (what you plug into a mobo) contained 8 or 9 memory chips on the board. These are the black chips you see on the outside of the module. Inside, these RAM chips were aligned in such a way that an equal portion of each byte of data is stored in each chip (each portion stored in a switch). These bytes, known as words, were then stored logically in address "pages." Each page holds pointers to the memory locations where the data for the word is held.
The banks of memory addresses they mention are these logical pages, and deal with the logical ordering of data stored in the chip. The term "Banks of switches" is probably their way of trying to tie the idea of logical ordering to the internal structure of the chip. Note that the RAM chips I'm describing are no longer ordered this way. This is why we see many RAM modules with 3-6 chips instead of the old 8 or 9.
3) & then
Scott Mueller says that dual-ranked memory has
internal banks of memory chips called ranks.
I think the ranks he's referring to are the words. IE, if a word was stored across multiple chips, think of the physical chip as vertically splitting data (think coloumns on a spreadsheet), while a rank would be horizontally splitting the data (think row)
(He was explaining why single-/double-sided memory has nothing to do with whether there's chip one one or both sides of a RAM stick, it's to do with memory ranks).
This could be true. Generally I see dual-sided memory having the RAM chips on both sides of the module, but this could be due to companies re-using cheap parts rather than being required.
I think my brain's gonna explode!
Mine already has...
Any help from the more theory inclined techs here would be much appreciated. Thanks!
Also, which is faster, single- or dual-rank (often called single-/double-sided memory)?
My pleasure. Also, neither is faster. Single/dual refers to (as stated above) how memory is stored in a chip, this won't influence speed. Speed is instead influenced by clockrate. Now actual chip statistics, such as how long it takes for electrical signals to stabilize inside of the chip, will influence speed as clockrates are set to give the characteristics of the hardware time to fully react or change state.
Hopefully this is all clear; let me know if it isn't. I could probably get more indepth into the mathematics and theory behind this stuff, but I'd honestly have to review it before I could remember it all. It's also well out of scope of anything expected to be known by a tech.
Edited by Insomnia, 22 December 2011 - 11:28 AM.
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