Dual Channel and Dual Ranked Memory?

Discussion in 'CPU, Motherboards and Memory' started by ddesantis79, Nov 20, 2007.

  1. ddesantis79

    ddesantis79 Geek Trainee

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    Hi everyone,

    I'm new to this forum, hoping someone can shed some light on a subject of dual ranked vs dual channel memory. I have a Dell PowerEdge 2800 server that requires either single or dual ranked memory (and only in certain combinations).

    One explanation on single vs dual ranked memory I found was this:

    Ranks are, simplistically, addressable memory locations.

    To get the best performance, you want to maximize the total number of ranks. For instance 4 1GB single rank DIMMs (4 total ranks) will give you better performance than 2 2GB single rank DIMMs (2 total ranks). The chipset will support up to 8 total ranks

    Think of it like spindles in RAID.

    However, dual ranked DIMMs are less expensive, so your choice is either best performance (maximize ranks) or lowest price (choose larger dual ranked pairs.)

    For the majority of applications you probably won't see a difference, but on real processor/memory intensive applicaitons like technical computing and HPCC you may see a difference, but in I/O heavy applicaitons like messaging and database you'll see less impact and should focus on best price.


    Now if I remember correctly, Dual Channel memory has to do with installing the memory in different pairs in the memory banks and it doubles the bandwidth as opposed to single channel memory.

    So the questions are:

    1. Is Dual Channel memory the same as Dual Ranked memory?
    2. How can you tell if memory is single or dual ranked? I never see anything on the packaging or on the chip (in my case PNY DDR2 PC2-5300 Dual Channel Memory)
     
  2. Big B

    Big B HWF Godfather

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    I'm not 100% sure, but it sounds like the ranks refer to the sides of the memory stick with RAM on them. RAM chips are placed on one or both sides of the stick. Single-sided (rank) has chips on one side only; dual-sided has chips on both sides of the stick.

    They may also mean banks, instead of ranks. It just might be a typo.
     
  3. ddesantis79

    ddesantis79 Geek Trainee

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    Nice logo Disturbed. :)

    Yes the dual ranks has to do with which sides the chips are installed on (for the most part from what I've found). I've also found that Ranks can be mistakenly called banks, but not channels. I'm fairly certain dual channel is different from dual rank, but I wanted to be sure. Mainly I need to find out how to tell if the memory is indeed dual rank (aside from looking at both sides of it and assuming as such).

    Side note: I tried googling the exact PNY memory part number and dual rank to see if it came up on an online store listed as such, and it doesn't. I think I'm narrowing this down, but its slow going...

    Also I did try PNY directly with their "free" tech support, which is about as useful as a shovel is for digging one's way out of a hole...
     

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