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Thread: มีคำถามเกี่ยวกับค่า CL ของแรมครับ

  1. #1
    OverclockZone Member Cesc's Avatar
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    18 Sep 2006
    Creative University

    Default มีคำถามเกี่ยวกับค่า CL ของแรมครับ

    คือว่า ผมไม่เข้าใจเรื่อง CL ของแรมอะครับ ช่วยอธิบายหน่อยครับ

    คือ CL 5 กับ CL 4 ต่างกันยังไงหรอครับ

    แล้วเราจะตั้งยังไงหรอครับ แบบว่า พวก 4-4-4-11 แบบนี้แล้วทำไมมันไม่เป็น

    4-4-4-12 อะครับ

    แล้วถ้า บัส 1000 แต่ CL5 กับ บัส 800 CL 4 นี่อันไหนแรงกว่ากันอะครับ



  2. #2
    OverclockZone Member romeo's Avatar
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    30 Sep 2006
    Arround The World



  3. #3
    OverclockZone Member Mcrxp's Avatar
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    6 Oct 2006


    งั้นต้องมี CL 0.025-0.025-0.025-0.025 รับรองแรงบรรลัย

  4. #4
    OverclockZone Member kingmax's Avatar
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    18 Sep 2006


    บัส 1000 แต่ CL5 แรงกว่าครับ ยิ่งใช้ เวลาน้อยเท่าไหร่ ยิ่งเข้าถึงข้อมูลได้เร็วมากขึ้น คับ

  5. #5
    OverclockZone Member pangpang's Avatar
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    16 Sep 2006


    Quote Originally Posted by Mcrxp View Post
    งั้นต้องมี CL 0.025-0.025-0.025-0.025 รับรองแรงบรรลัย

  6. #6
    OverclockZone Member KUTTO's Avatar
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    10 Dec 2006


    ง่ายๆค่าCL ตัวเลขยิ่งน้อยยิ่งดีนะ เข้าถึงข้อมูลไวแต่เค้ามะให้ต่ำกว่า2อยู่แล้ว

  7. #7
    OverclockZone Member pvp's Avatar
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    27 Nov 2006
    Alone in Darkness


    Next came dual-channel config, where two mem-sticks help each other out. Think of it as a RAID0 for memory... ;-) Hence, again, double speed. 800 becomes 1600.

    DRAM CAS Latency
    DRAM RAS# Precharge
    DRAM RAS# to CAS# Delay
    DRAM RAS# Activate to Precharge Delay
    DRAM Write Recovery Time

    These are the memory-timing settings. How to set largely depends on your memory and speed and depends even more on the speed you've set your memory to run on. Whether these will have a great impact on your memories performance depends largely on the type of memory used.

    DRAM CAS Latency
    In theory, take DDR2-800 memory.
    It supports several speeds, each having a unique CAS-Latency. In general, the faster the speed, the higher the latency needed to keep up. The base frequncies come from SD-RAM and you should think of them as multipliers, not the actual freq. DDR2 is running on.
    DDR2- 400 533 667 800
    Base-freq. 100 133 166 200
    CL CL2 CL3 CL4 CL5

    So, for any memory-frequency, you should choose a corresponding CL. In this case, for xample, if you make this memory run as
    DDR2-800 or faster: CL should be 5
    DDR2-667 - DDR2-800: CL should be 4
    DDR2-533 - DDR2-667: CL should be 3
    DDR2-400 - DDR2-533: CL should be 2

    Note I say "should be", because sometimes, with good memory, it's possible to make the memory run as DDR2-533 memory, but overclocked so much that it falls into the next range. In other words, you could try to overclock it so much as DDR2-533 that it would still be running with CL3, while the frequency is set to DDR2-700. However, this usually requires applying a well-dozed amount of overvoltage, which can shorten your memories lifetime, and also make your memory run much hotter than normal, heatspreaders highly recommended then... ;-)

    Note though that not all memory supports all configs, for example my own DDR2-667 memory supports
    Mhz 100 133 166
    CL CL3 CL4 CL5
    From this alone you can see my memory is not so great :-(

    Most Corsair-667 and Crusial-667 memory for example can do this:
    Mhz 100 133 166
    CL CL2 CL3 CL4
    Much better! Much more expensive too, unfortunately... :-(

    Some DDR2-800 memory might look like this:
    Mhz 200
    CL CL4
    In other words, SPD-tables are not complete. This will make it more difficult to run it at other speeds, but with extrapolation you should be able to figure it out, for example, this memory MIGHT run as DDR2-667 on CL3. Then again, it might simply refuse to run on other latencies all
    together. Well, only one way to find out! LOL

    Anyway, point I'm trying to make is that you should set your memory-frequency to something that can support the CL you're trying to set, and vice versa. With mem. frequency I mean anything that divide by these base-frequencies, so setting DDR2-600 (due to overclocking) means your memory might support it as OVERclocked DDR2-533 memory with CL set to the number corresponding the base-frequency, which is 133, so for our example memory, CL3. You can also configure it as DOWNclocked DDR2-667 memory with CL4. This little bit of calculating is required to find your best timings at a given memory-speed. Downclocking ofcourse is never desireable but most of the times necessary to combine the best setting for memory and CPU. It usually gives better performance though to lower your timings one step, set your memory-speed
    divider one step lower and lower your CPU-speed to match, ie. in our example here, the OVERclocked DDR2-533 setting with CL3 gives better performance with lower CPU-speed than
    DOWNclocked at 667Mhz. with slightly higher CPU-speed. However, you can only do so, if your memory stays stable at an overclocked frequency of 600 Mhz.

    Ofcourse, Any memory-frequency setting above the default frequency you bought is overclocking, in which case the limit you can reach is really the top your memory will run at (And that's the first limit you should figure out). You cannot make DDR2-533 memory run as DDR2-800 memory with a frequency of 800. However, some good memory can do so, as long as you adjust your timings, which would be rediculously high CL-settings. The purpose of doing so
    however can only be fun, because performance would suck. Idea of all this now is to make your memory run at the lowest CL with the highest memory-frequency possible closest matching your CPU-frequency (FSB-frequency). By the way, don't confuse your CPU-frequency with the FSB- frequency. The value you see at CPU-frequency is the actual original frequency that gets multiplied with the CPU-multiplier, which is mostly locked on most procs. Mine for example has a multiplier of 16, so 16x200 is stock CPU-frequency of 3200 Mhz. That 16 is fixed, so I can only raise the 200 to overclock. However, your FSB-speed (Speed between CPU and Memory-controller HUB) is also fixed to that base-frequency of 200, it's a x4 multiplier, bringing your stock FSB-speed to 4x200=800 Mhz. Overclocking your CPU thus means overclocking your
    Memory-controller (Unless you're using a PD955 @ 1066Mhz FSB, this memory-contoller should have no problems running any FSB between 800-1066, since it's desinged to supoprt FSB1066!). In between is another multiplier (Divider actually) and that's your memory-divider, dividing the CPU-frequency (200 Mhz) with a divider to get the memory-speed. The memory-speed-settings you can choose are actually divider settings like 1/3, 2/3, 1/2, 1/1, etc. Your aim
    now is to set the lowest divider giving you most of your overclocked frequency for as far as your memory can support it with the lowest possible CAS latency. In short:
    mem-speed = CPU / mem-divider
    CPU-internal freq. = CPU x CPU-multiplier
    FSB = CPU x 4

    DRAM RAS# Precharge
    This value is mostly set to the same as CAS#, however, some memory has no problem lowering this down.

    DRAM RAS# to CAS# Delay
    This should in most cases be set the same as CAS#.

    DRAM RAS# Activate to Precharge Delay
    This can in most cases be set to CAS# x3. Some memory allows lower than that, some can do with CAS# x2, some even with CAS# x1!

    DRAM Write Recovery Time
    This should in most cases be set to CAS#+1, however, some memory has no problem lowering this down.

    I actually wanted to explain each in detail, but I think it's more usefull to skip the technical details and come to the point of what is of importance setting these. I figured that would make more sense. Any detailed info on these can easily be found on the net using Google anyway. I tried to explain the CAS#-setting in detail however, because you can set the rest based on that one. As a rule of thumb, to start out with,
    set your "CAS#",
    set your "RAS# to CAS#" the same,
    set your "RAS# Activate to Precharge" to x3 "CAS#",
    set your "RAS# Precharge" to "CAS#",
    set your "DRAM Write Recovery Time" to "CAS#"+1

    example with CAS# Latency 5:
    DRAM CAS# Latency: 5
    DRAM RAS# Precharge: 5
    DRAM RAS# to CAS# Delay: 5
    DRAM RAS# Activate to Precharge Delay: 15
    DRAM Write Recovery Time: 6

    From here, just don't touch "DRAM CAS# Latency" and "DRAM RAS# to CAS# Delay" and simply try to lower the rest one by one. Memory-testing at each step/change is important
    because just changing and seeing if you can boot back into the BIOS is NOT enough!!!
    On each change, load Windows and do Prime95 mem-stresstesting to make sure your memory can handle it. The easiest however is, to do this phase (finetuning your individual memory-timings) as the last step.

    An example:
    You have DDR2-800, your base-frequency then is 200 Mhz.
    your memory supports
    Mhz 100 133 166 200
    CL CL2 CL3 CL4 CL5
    Your CL is then 5. If you set your memory-frequency-divider to DDR2-800 (1/2 @ FSB200), you are running stock. If you then raise your CPU-frequency you will push the memory beyond the 200 Mhz base-freq. At some point, your memory will give up, say this memory gives up at 883 Mhz, then your base-frequency is 883 x 1/2 mem-divider x 1/2 base-divider= 220.75 Mhz on CL5
    Basically, you can then interpolate the max it will run on as DDR2-667 memory as 883/800 x 667 = 736 Mhz on CL4

    Pushing it beyond 736 probably will give you the same result as pushing it beyond 883 Mhz: it gives up. Same running it as DDR2-533 as 883/800 x 533 = 588 Mhz on CL3.

    You usually can succesfully push your memory further beyond it's design limit by adding overvoltage to it. Standard DDR2 needs 1.8 Volts according to spec., but in most cases you can push that as far as 2.2 Volts. Some even more, others have the max. voltage printed on the package or supplied manual, others you can find on the manufacturers website. If you can't find the max. voltage though (Unknown brand memory), be carefull and keep it safe by not pushing it beyond 2.0 volts max. !!! Just to be save. Memory has become alot cheaper, but still is expensive enough to keep it a little safe! For any component: If you apply over-voltage you ARE
    really shortening it's lifetime, and the scale at which you shorten it's life is NOT a linear scale! A little overvoltage will still shorten the components life, but a life of 10 years or 6 years on a little overvoltage is tolerable in most cases, and that's why a little overvoltage doesn't really hurt.
    ASUS has provided some safety while setting voltages, by color-coding the numbers. If it's getting riscy, numbers show purple. If it's getting dangerous, numbers get red. As a rule of thumb, stick with the white numbers.

  8. #8
    OverclockZone Member benzmore's Avatar
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    17 Dec 2006


    มีบอร์ดบางตัว ปรับได้ถึง 1.5 คับ



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