What speed RAM?

Discussion in 'Computer Information' started by tempus fugit, Nov 10, 2007.

  1. tempus fugit

    tempus fugit Guest

    Hey all;

    I'm thinking about upgrading to an Athlon X2 3800+ - 4400+ CPU. Can anyone
    tell me the speed of RAM I need for these processors? I'm a little lost on
    the FSB to RAM relationship these days.

    Thanks
     
    tempus fugit, Nov 10, 2007
    #1
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  2. tempus fugit

    Paul Guest

    tempus fugit wrote:
    > Hey all;
    >
    > I'm thinking about upgrading to an Athlon X2 3800+ - 4400+ CPU. Can anyone
    > tell me the speed of RAM I need for these processors? I'm a little lost on
    > the FSB to RAM relationship these days.
    >
    > Thanks


    What motherboard ? Just to confirm, are we talking AM2 and DDR2 ?

    Here is an example, Asus Crosshair - "DDR2-800/667/533"
    http://www.asus.com/products4.aspx?modelmenu=2&model=1283&l1=3&l2=101&l3=300&l4=0

    Next, shoot for something cheap, like an Asus VIA based board, and it's
    the same thing - "DDR2 800/667/533"
    http://www.asus.com/products4.aspx?modelmenu=2&model=1418&l1=3&l2=101&l3=324&l4=0

    The memory controller is inside the processor, which is why the spec
    doesn't change.

    There are some math examples here, of how the processor
    selection makes a minor difference to actual RAM operating speed.
    But basically, at stock settings, DDR2-800 covers it and is the
    top official speed grade.

    http://www.hardwaresecrets.com/article/340

    As for how much higher than DDR2-800 to go for, that depends on how fast
    the AMD processors will run RAM. The spec in the motherboard manual,
    assumes a non-overclocked processor. In other words, a processor whose
    master clock is still 200MHz. If you raise the master clock, everything
    goes faster, including the RAM. You can change memory dividers, to bring
    the speed down, or you could leave it and let it run faster than
    normal. But at some point, the bus drivers on the processor simply
    cannot reliably clock high enough. I would expect the processor to
    run out of steam, before the memory sticks do. To find out how high
    the processor memory interface can go, you're going to have to visit
    a few web sites (overclocker sites).

    If it was me, I'd just pick up some DDR2-800 CAS5 (standard grade, in
    effect) and just enjoy it.

    And if your budget is tight, a pair of DDR2-533 sticks will still work
    just fine.

    Your best purchase, is to go dual channel, so if you wanted 1GB total,
    buy 2x512MB. If you wanted 2GB, buy 2x1GB sticks. The last time I looked,
    the lowest price on memory was about $25 per 1GB stick (but the DDR2-800
    stuff will likely be more than that). Use the reviews on Newegg, to get
    some idea which brands and model numbers don't have a lot of DOAs or badly
    binned sticks. Once you've spotted a good brand, you can even pick it up
    at a local computer store (makes it easier to return if it is defective).

    Paul
     
    Paul, Nov 10, 2007
    #2
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  3. tempus fugit

    tempus fugit Guest

    "Paul" <> wrote in message news:fh4nic$luo$...
    > tempus fugit wrote:
    > > Hey all;
    > >
    > > I'm thinking about upgrading to an Athlon X2 3800+ - 4400+ CPU. Can

    anyone
    > > tell me the speed of RAM I need for these processors? I'm a little lost

    on
    > > the FSB to RAM relationship these days.
    > >
    > > Thanks

    >
    > What motherboard ? Just to confirm, are we talking AM2 and DDR2 ?
    >
    > Here is an example, Asus Crosshair - "DDR2-800/667/533"
    >

    http://www.asus.com/products4.aspx?modelmenu=2&model=1283&l1=3&l2=101&l3=300&l4=0
    >
    > Next, shoot for something cheap, like an Asus VIA based board, and it's
    > the same thing - "DDR2 800/667/533"
    >

    http://www.asus.com/products4.aspx?modelmenu=2&model=1418&l1=3&l2=101&l3=324&l4=0
    >
    > The memory controller is inside the processor, which is why the spec
    > doesn't change.
    >
    > There are some math examples here, of how the processor
    > selection makes a minor difference to actual RAM operating speed.
    > But basically, at stock settings, DDR2-800 covers it and is the
    > top official speed grade.
    >
    > http://www.hardwaresecrets.com/article/340
    >
    > As for how much higher than DDR2-800 to go for, that depends on how fast
    > the AMD processors will run RAM. The spec in the motherboard manual,
    > assumes a non-overclocked processor. In other words, a processor whose
    > master clock is still 200MHz. If you raise the master clock, everything
    > goes faster, including the RAM. You can change memory dividers, to bring
    > the speed down, or you could leave it and let it run faster than
    > normal. But at some point, the bus drivers on the processor simply
    > cannot reliably clock high enough. I would expect the processor to
    > run out of steam, before the memory sticks do. To find out how high
    > the processor memory interface can go, you're going to have to visit
    > a few web sites (overclocker sites).
    >
    > If it was me, I'd just pick up some DDR2-800 CAS5 (standard grade, in
    > effect) and just enjoy it.
    >
    > And if your budget is tight, a pair of DDR2-533 sticks will still work
    > just fine.
    >
    > Your best purchase, is to go dual channel, so if you wanted 1GB total,
    > buy 2x512MB. If you wanted 2GB, buy 2x1GB sticks. The last time I looked,
    > the lowest price on memory was about $25 per 1GB stick (but the DDR2-800
    > stuff will likely be more than that). Use the reviews on Newegg, to get
    > some idea which brands and model numbers don't have a lot of DOAs or badly
    > binned sticks. Once you've spotted a good brand, you can even pick it up
    > at a local computer store (makes it easier to return if it is defective).
    >
    > Paul


    Sorry, should have specified - it's Socket 939

    RThanks
     
    tempus fugit, Nov 10, 2007
    #3
  4. tempus fugit

    Paul Guest

    tempus fugit wrote:
    > "Paul" <> wrote in message news:fh4nic$luo$...
    >> tempus fugit wrote:
    >>> Hey all;
    >>>
    >>> I'm thinking about upgrading to an Athlon X2 3800+ - 4400+ CPU. Can

    > anyone
    >>> tell me the speed of RAM I need for these processors? I'm a little lost

    > on
    >>> the FSB to RAM relationship these days.
    >>>
    >>> Thanks


    >> What motherboard ? Just to confirm, are we talking AM2 and DDR2 ?


    >
    > Sorry, should have specified - it's Socket 939
    >
    > RThanks
    >


    A couple sticks of PC3200 memory should do the trick. The best config
    for S939, is no more than two sticks. If you use four sticks in dual
    channel mode, the clock rate or the command rate setting would have
    to change. With two sticks you can run DDR400 Command Rate 1T. With
    four sticks you might try DDR400 Command Rate 2T or DDR333 Command
    Rate 1T.

    For DDR memory, the only memory I'd avoid, is 1GB DDR memory from
    Ebay. A lot of that memory is "high density", and branded memory
    like stuff from Crucial, Kingston, Corsairmicro etc., will be
    low density and easier for the processor to drive. My mission in
    life, is to see as little of that Ebay stuff get into circulation,
    as is possible. If you want to buy 512MB DDR memory off Ebay,
    there are no density tricks for that stuff (but try to get two
    matching sticks - if one has 16 chips, so should the other one).

    Again, on S939, the memory controller is inside the processor. So
    any issues you see, would be processor related.

    Paul
     
    Paul, Nov 11, 2007
    #4
  5. tempus fugit

    tempus fugit Guest

    "> A couple sticks of PC3200 memory should do the trick. The best config
    > for S939, is no more than two sticks. If you use four sticks in dual
    > channel mode, the clock rate or the command rate setting would have
    > to change. With two sticks you can run DDR400 Command Rate 1T. With
    > four sticks you might try DDR400 Command Rate 2T or DDR333 Command
    > Rate 1T.
    >
    > For DDR memory, the only memory I'd avoid, is 1GB DDR memory from
    > Ebay. A lot of that memory is "high density", and branded memory
    > like stuff from Crucial, Kingston, Corsairmicro etc., will be
    > low density and easier for the processor to drive. My mission in
    > life, is to see as little of that Ebay stuff get into circulation,
    > as is possible. If you want to buy 512MB DDR memory off Ebay,
    > there are no density tricks for that stuff (but try to get two
    > matching sticks - if one has 16 chips, so should the other one).
    >
    > Again, on S939, the memory controller is inside the processor. So
    > any issues you see, would be processor related.
    >
    > Paul


    Thanks again Paul. So the earlier memory you mentioned (which is so damn
    cheap right now) is not compatible with a socket 939 mobo, or the PC3200 is
    preferable? I think the board I have now has PC 2700 in it, which I assume
    would be OK as well. Also, if the FSB is 1000, I thought the RAM used would
    be 500 (or 533 in this case). I guess this is where I'm confused because the
    last time I put together a system that was the general rule.

    Thanks
     
    tempus fugit, Nov 11, 2007
    #5
  6. tempus fugit

    Paul Guest

    tempus fugit wrote:
    > "> A couple sticks of PC3200 memory should do the trick. The best config
    >> for S939, is no more than two sticks. If you use four sticks in dual
    >> channel mode, the clock rate or the command rate setting would have
    >> to change. With two sticks you can run DDR400 Command Rate 1T. With
    >> four sticks you might try DDR400 Command Rate 2T or DDR333 Command
    >> Rate 1T.
    >>
    >> For DDR memory, the only memory I'd avoid, is 1GB DDR memory from
    >> Ebay. A lot of that memory is "high density", and branded memory
    >> like stuff from Crucial, Kingston, Corsairmicro etc., will be
    >> low density and easier for the processor to drive. My mission in
    >> life, is to see as little of that Ebay stuff get into circulation,
    >> as is possible. If you want to buy 512MB DDR memory off Ebay,
    >> there are no density tricks for that stuff (but try to get two
    >> matching sticks - if one has 16 chips, so should the other one).
    >>
    >> Again, on S939, the memory controller is inside the processor. So
    >> any issues you see, would be processor related.
    >>
    >> Paul

    >
    > Thanks again Paul. So the earlier memory you mentioned (which is so damn
    > cheap right now) is not compatible with a socket 939 mobo, or the PC3200 is
    > preferable? I think the board I have now has PC 2700 in it, which I assume
    > would be OK as well. Also, if the FSB is 1000, I thought the RAM used would
    > be 500 (or 533 in this case). I guess this is where I'm confused because the
    > last time I put together a system that was the general rule.
    >
    > Thanks


    There isn't a classical FSB in the normal sense, on Athlon64.

    On Intel, everything is a lot simpler. There is the processor (with no memory
    controller on it). There is the Northbridge (which has the memory controller).
    The FSB connects them together, and is a bottleneck. There is some
    (potential) relationship, between the FSB choice, and the memory there.

    On Athlon64, the memory controller is inside the processor. That means
    there is no traditional external bus to get in the way. There is a front
    side bus, but it is called Hypertransport. It connects the processor to
    the Northbridge. The Northbridge would have something like a video card
    interface on it. If you drop the speed of the Hypertransport interface,
    it slowly eats into your video performance. (So 5x200 would be full
    Hypertransport speed, 4x200 is a bit of a slowdown, and you might not even
    notice the effects while gaming. One you drop to 1x200, then you'll be
    losing a couple thousand in 3DMark.)

    Inside the processor, the input clock (200MHz) is multiplied by the core
    multiplier. 12X would get you to 2.4GHz, for example.

    To make a clock signal for the memory, they use a divider that runs from
    the core clock. They use the nearest divider that meets the target clock
    rate for the memory. If they wanted to run at DDR333, they pick a divider
    that makes a 166Mhz or slight lower memory clock (2.4GHz/15 = 160MHz, or
    DDR320). If you set DDR400 in the BIOS, a smaller memory divider is used
    to get a higher memory clock (2.4GHz/12 = 200Mhz, or DDR400). Because
    the combination of multiplying up, and dividing down, doesn't always
    give exactly the right clock speeds, the available tables will list some
    weird values for the actual clock used.

    I think DDR400 is the highest standard speed defined in JEDEC, which is
    why you'd see that in an AMD document. Enthusiast products have been
    tested up to DDR600, which means for bags of money, you can get a
    faster memory. The question would be, whether with the appropriate
    overclock settings, you can get all the bandwidth offered by the
    DDR600 memory or not. As explained in the other posting about AM2,
    yes, you can buy memory above the design limits. DDR2-800 is the
    official top for AM2, and DDR400 is the official top for S939. But
    if you drop the core multiplier, raise the input clock, it is possible
    to make that DDR400 setting, give higher memory clocks than that.
    (That is because the processor doesn't know it is being overclocked,
    so it has no opportunity to use a different divider. The design
    assumption is, that the input clock is a 200MHz constant.)

    This is an example of some experiments at DDR600. Notice that the
    sticks are of smaller capacity. I don't know if anyone makes 1GB
    sticks that go as high as some of these. (Plenty of room for research
    there, though. And DDR is not as popular as it once was, so some of
    these products will have disappeared from retail.)

    http://www.xtremesystems.org/forums/showthread.php?t=57317

    You can see the test conditions here.

    http://img467.imageshack.us/img467/1817/275MHZ_DC_GSKILL_1GBLE_sandra.jpg

    Input clock changed from 200MHz to 275Mhz. If the DDR400 memory
    setting is select on that motherboard, the bump in clock should
    take it to DDR550. The multiplier was set to 9x for the core, and
    the core is running 2475. You want to set the multiplier, so the
    core doesn't run faster than it is capable of. And the various
    processors each have a range of multipliers they support, say
    6x..9x or whatever. So you need the right processor, to get a
    useful range of multipliers. Some processors have unlocked
    multipliers (perhaps all the FX series ?), in which case
    there might be a little more freedom to juggle the numbers.

    With no overclock, DDR400 (PC3200) is a good choice. The processor
    will use a divider, that gives a clock suitable for DDR400. But
    by cheating (bump input clock, but the processor doesn't know),
    it is possible to raise the memory clock higher than that. High
    enough, that eventually the bus cannot run that fast and you
    get memory errors. There are limits, to how much improvement
    you can get by bumping up various voltages.

    For best results, use two sticks. There is no point buying four
    sticks of DDR600 memory, because the memory controller definitely
    cannot drive that load at DDR600. Two sticks, one per channel, is
    a better choice in that regard. 2x512MB might allow the most
    heroic memory bus settings and results. 2x1GB will likely end
    up with a slightly lower frequency, not because the technology
    is inherently that much different, but because the industry
    moved on to working on DDR2, before there was a real chance
    to crank the hell out of 1GB sticks.

    HTH,
    Paul
     
    Paul, Nov 11, 2007
    #6
  7. tempus fugit

    tempus fugit Guest

    "Paul" <> wrote in message news:fh6ocb$77q$...
    > tempus fugit wrote:
    > > "> A couple sticks of PC3200 memory should do the trick. The best config
    > >> for S939, is no more than two sticks. If you use four sticks in dual
    > >> channel mode, the clock rate or the command rate setting would have
    > >> to change. With two sticks you can run DDR400 Command Rate 1T. With
    > >> four sticks you might try DDR400 Command Rate 2T or DDR333 Command
    > >> Rate 1T.
    > >>
    > >> For DDR memory, the only memory I'd avoid, is 1GB DDR memory from
    > >> Ebay. A lot of that memory is "high density", and branded memory
    > >> like stuff from Crucial, Kingston, Corsairmicro etc., will be
    > >> low density and easier for the processor to drive. My mission in
    > >> life, is to see as little of that Ebay stuff get into circulation,
    > >> as is possible. If you want to buy 512MB DDR memory off Ebay,
    > >> there are no density tricks for that stuff (but try to get two
    > >> matching sticks - if one has 16 chips, so should the other one).
    > >>
    > >> Again, on S939, the memory controller is inside the processor. So
    > >> any issues you see, would be processor related.
    > >>
    > >> Paul

    > >
    > > Thanks again Paul. So the earlier memory you mentioned (which is so damn
    > > cheap right now) is not compatible with a socket 939 mobo, or the PC3200

    is
    > > preferable? I think the board I have now has PC 2700 in it, which I

    assume
    > > would be OK as well. Also, if the FSB is 1000, I thought the RAM used

    would
    > > be 500 (or 533 in this case). I guess this is where I'm confused because

    the
    > > last time I put together a system that was the general rule.
    > >
    > > Thanks

    >
    > There isn't a classical FSB in the normal sense, on Athlon64.
    >
    > On Intel, everything is a lot simpler. There is the processor (with no

    memory
    > controller on it). There is the Northbridge (which has the memory

    controller).
    > The FSB connects them together, and is a bottleneck. There is some
    > (potential) relationship, between the FSB choice, and the memory there.
    >
    > On Athlon64, the memory controller is inside the processor. That means
    > there is no traditional external bus to get in the way. There is a front
    > side bus, but it is called Hypertransport. It connects the processor to
    > the Northbridge. The Northbridge would have something like a video card
    > interface on it. If you drop the speed of the Hypertransport interface,
    > it slowly eats into your video performance. (So 5x200 would be full
    > Hypertransport speed, 4x200 is a bit of a slowdown, and you might not even
    > notice the effects while gaming. One you drop to 1x200, then you'll be
    > losing a couple thousand in 3DMark.)
    >
    > Inside the processor, the input clock (200MHz) is multiplied by the core
    > multiplier. 12X would get you to 2.4GHz, for example.
    >
    > To make a clock signal for the memory, they use a divider that runs from
    > the core clock. They use the nearest divider that meets the target clock
    > rate for the memory. If they wanted to run at DDR333, they pick a divider
    > that makes a 166Mhz or slight lower memory clock (2.4GHz/15 = 160MHz, or
    > DDR320). If you set DDR400 in the BIOS, a smaller memory divider is used
    > to get a higher memory clock (2.4GHz/12 = 200Mhz, or DDR400). Because
    > the combination of multiplying up, and dividing down, doesn't always
    > give exactly the right clock speeds, the available tables will list some
    > weird values for the actual clock used.
    >
    > I think DDR400 is the highest standard speed defined in JEDEC, which is
    > why you'd see that in an AMD document. Enthusiast products have been
    > tested up to DDR600, which means for bags of money, you can get a
    > faster memory. The question would be, whether with the appropriate
    > overclock settings, you can get all the bandwidth offered by the
    > DDR600 memory or not. As explained in the other posting about AM2,
    > yes, you can buy memory above the design limits. DDR2-800 is the
    > official top for AM2, and DDR400 is the official top for S939. But
    > if you drop the core multiplier, raise the input clock, it is possible
    > to make that DDR400 setting, give higher memory clocks than that.
    > (That is because the processor doesn't know it is being overclocked,
    > so it has no opportunity to use a different divider. The design
    > assumption is, that the input clock is a 200MHz constant.)
    >
    > This is an example of some experiments at DDR600. Notice that the
    > sticks are of smaller capacity. I don't know if anyone makes 1GB
    > sticks that go as high as some of these. (Plenty of room for research
    > there, though. And DDR is not as popular as it once was, so some of
    > these products will have disappeared from retail.)
    >
    > http://www.xtremesystems.org/forums/showthread.php?t=57317
    >
    > You can see the test conditions here.
    >
    > http://img467.imageshack.us/img467/1817/275MHZ_DC_GSKILL_1GBLE_sandra.jpg
    >
    > Input clock changed from 200MHz to 275Mhz. If the DDR400 memory
    > setting is select on that motherboard, the bump in clock should
    > take it to DDR550. The multiplier was set to 9x for the core, and
    > the core is running 2475. You want to set the multiplier, so the
    > core doesn't run faster than it is capable of. And the various
    > processors each have a range of multipliers they support, say
    > 6x..9x or whatever. So you need the right processor, to get a
    > useful range of multipliers. Some processors have unlocked
    > multipliers (perhaps all the FX series ?), in which case
    > there might be a little more freedom to juggle the numbers.
    >
    > With no overclock, DDR400 (PC3200) is a good choice. The processor
    > will use a divider, that gives a clock suitable for DDR400. But
    > by cheating (bump input clock, but the processor doesn't know),
    > it is possible to raise the memory clock higher than that. High
    > enough, that eventually the bus cannot run that fast and you
    > get memory errors. There are limits, to how much improvement
    > you can get by bumping up various voltages.
    >
    > For best results, use two sticks. There is no point buying four
    > sticks of DDR600 memory, because the memory controller definitely
    > cannot drive that load at DDR600. Two sticks, one per channel, is
    > a better choice in that regard. 2x512MB might allow the most
    > heroic memory bus settings and results. 2x1GB will likely end
    > up with a slightly lower frequency, not because the technology
    > is inherently that much different, but because the industry
    > moved on to working on DDR2, before there was a real chance
    > to crank the hell out of 1GB sticks.
    >
    > HTH,
    > Paul


    Well, that's all fairly simple...

    I think I'm following that anyway. Thanks for all your help Paul
     
    tempus fugit, Nov 12, 2007
    #7
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