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Why does memory divider matter?

Discussion in 'Motherboards & Memory' started by CarolinaKSU, Nov 6, 2008.

  1. CarolinaKSU New Member

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    I have seen alot of talk where people say you need a 1:1 memory divider or 4:5 or whatever. However, if I set my ram to 1:1 in the bios, i get a speed of like 1350, which is of course wayyy up there for DDR2, and all I am running is an E6600 with a 378mhz FSB (x9 for 3.4 ghz).

    So i have my memory set as unlinked and ticking along at 1100mhz, their stock speed with a 11:16 FSB to RAM ratio. So my question is why does that divider matter and why should I slow down my RAM to match something PC2-6400 RAM has no problem with?
  2. spearman914

    spearman914 New Member

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    The divider matters so you don't under clock ram too much or oc ram too much. Lets say you got 400 MHz FSB and PC6400 800 MHz with a 1:2 divider. This causes ram to go up to a rough 1.6 GHz!!!! Of course that won't be stable so it is important.

    Also it's important in a case like you have a 266 FSB CPU and have 800 MHz ram and you want the 266 FSB but you want 800 MHz to stay the same so you would put the 4:6 to make it stable (can't find a better word..) .
  3. panchoman

    panchoman Sold my stars!

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    the fsb controls the memory speed. as fsb increases, the ram speed does as well. the divider changes the ratio between the fsb and ram speed.. it's used to manage the ram speed. for example, if you push your fsb higher, you'll need to drop it to a lower divider otherwise your ram will go too high and cause problems and failures. you can also use dividers to get your ram at a higher speed with less fsb.
  4. CarolinaKSU New Member

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    Interesting.. so what can I do to take stress off of the RAM in order to close the gap in the divider but keep the speed up? I was trying to take my CPU o/c up to 3.6ghz a while back and it just would hit a brick wall anything higher than 3.4 and not stay stable at all. Would that have something to do with my huge gap in RAM speed vs FSB? What can I do to have something close to a 1:1 ratio that wouldnt be some astronomical speed?

    [​IMG]

    [​IMG]
  5. spearman914

    spearman914 New Member

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    Set ram divider to 1:1 to lower ram. Ur ram is tad high at speeds. Set Vcoer to Vcore 1.55 iftemps are ok.
  6. CarolinaKSU New Member

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    Thats the problem I have been having, when i go into the bios, I change the memory to "linked" as the bios says and the ratio 1:1 and i get a huge value for the ram that causes my machine to not even post.
  7. spearman914

    spearman914 New Member

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    Change it to unlink. If that doesn't work then thats messed up. Try flashing the bios.
  8. CarolinaKSU New Member

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    Unlinked is what i have it set to now, with the rated speed of the memory manually entered. I should just leave it unlinked and manually slow down my ram speed to match the FSBx2 for dual channel?
  9. panchoman

    panchoman Sold my stars!

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    just manually set your ram to a slower speed, and if it increases with your fsb still, then it'll go back up to normal, and if it doesn't, you can always boost it back up later.
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  10. CarolinaKSU New Member

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    Gotcha, I will give that a try and see what happens.
  11. EastCoasthandle

    EastCoasthandle New Member

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    As a rule of thumb you want to maintain your ram's default speed unless you are stable at a higher speed. You only go lower if you have a stability problem, nothing more nothing less. I've read that some were lowering their ram's speed because someone told them which is completely wrong. By doing so you can decrease performance.

    Whenever you overclock your CPU try to get the most stable ram speed possible. That's one of the reasons why DDR2 1066 is so popular over DDR2 800 IMO. The average that most will get with DDR2 800 is about 950MHz. The average for DDR2 1066 is about 1100MHz (from what I've seen around the net). Does higher ddr2 make a difference? Well I have both kits and from my own experience it does make a difference. Not just in games but how long it takes to load up the OS and execute other programs.

    When you overclock your CPU you want to overclock your memory as well. That's the name of the game, stick to that and you should do alright. Just make sure you don't over volt your ram. Only use the recommended voltage (in most cases, depending on the IC used) for your ram. That's the one thing that can and will kill your ram (over volting).
  12. Kursah

    Kursah

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    I think it depends on a few things and on a per application basis. It's more important for Intel Chipset users that cannot unlink their memory from the FSB speeds like the NV boards can. This can create a very limiting barrier depending on the speed of memory used and it's capabilities of overclocking. So then if you're on an Intel chipset, 1:1 is good for 400+ FSB depending on what memory you have, some dividers will give you 1000, 1066, 1200 etc speeds using different dividers at 400FSB. Pretty much beyond the magical 400 number here, things get a little more in-depth for speeds and much more limited to the lower value creating dividers unless you have some really stellar memory. This is something I keep in mind when I overclock as I do prefer Intel based boards since I have more experience with them, so that tells me that for most of my OC's which run between 400-500FSB, I need DDR800-1000 capable memory. Sure being able to go beyond is an ok thing, but I haven't really seen a need for it in anything I do from browsing to gaming.

    On NV chipsets and other chipsets that allow unlinking of memory, it's a nice feature to be able to independantly OC the system bus/CPU from the memory and vice-versa. And I would have to say, the memory speed divider here becomes less necessary.

    That's my take on it at least! :toast:
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  13. CarolinaKSU New Member

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    My ram is running at its default speed now (1100mhz) right now, it just has a wicked stupid divider of 11:16. Now I am beyond confused, because youre right lowering the speed in the bios and restarting did nothing except give me slower ram..
  14. CarolinaKSU New Member

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    Kursah, that was sort of my opinion on it too. Since I have a 680i board, it makes more sense that being able to change my memory speed completely independently of the FSB makes the divider sort of irrelevant. Can I safely say that clocking my FSB as far as it can reasonably go and leave my memory clocked as far as it can reasonably go (in my case, just leaving it stock) is the way to go with my setup and just leave it as is with that wacky divider?
  15. Kursah

    Kursah

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    If it's not an issue now, I don't see a problem man. If you can run both OC'd with stability and have no crashing, issues, I'd say go with it, you're using those features how they were in a sense designed to work. If I had the option on my board I'd be taking the same route and ridding my limitations of dividers.

    :toast:
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  16. CarolinaKSU New Member

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    Thanks for the quick help everyone.. One question does remain however. Why does the RAM speed shoot up so fast, even though my actual FSB is only 378mhz? Wouldn't the RAM speed be 760mhz-ish if i linked the FSB 1:1?

    Also, I am including a crappy phone pic of my bios screen in question that shows the ram speeds going through the roof.

    [​IMG]
  17. mlee49

    mlee49

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    It is since it's double data rate. 775/2=377.

    I question the necessity as well to run a 1:1 ratio. Is the preformance that noticble?
  18. Greg0101 Memory Expert

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    On this motherboard. Whats known as 1:1 is actually. Linked Memory Mode , Sync for speed.
    800Mhz 4-44-12 @ 1600FSB normally wins in test over 1066Mhz 5-5-5-15 unlinked, eventually you can get unlinked to perf better with higher speeds. But wouldn't beat a higher fsb speed running memory in sync.

    At stock speeds, sync is the best, since it takes close to 1200Mhz to beat 667Mhz 4-4-4-12 in sync.

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