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Thread: tREAD and CAS Latency?




  1. #11
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    Default Re: tREAD and CAS Latency?

    Quote Originally Posted by gampamu View Post
    The allowable tRD setting depends on 3 settings: CAS latency, FSB, and the DRAM to FSB ratio. Low CAS latency, low FSB and high DRAM to FSB ratio favor lower tRD settings.

    A good read on the subject: AnandTech: ASUS ROG Rampage Formula: Why we were wrong about the Intel X48.
    That's an excelent article. I was about to recommand the same link, but gampamu beat me to it. Give it a thorough read and everything will become clear.
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  2. #12
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    Default Re: tREAD and CAS Latency?

    Quote Originally Posted by morph View Post
    That's an excelent article. I was about to recommand the same link, but gampamu beat me to it. Give it a thorough read and everything will become clear.
    Ok, I've read it a few times thorough, now;
    (I actually read it once before a few weeks ago, before starting this thread...)
    but am not really able to glean that much from it.
    Mostly because it focuses upon DRAM performance,without considering overall system performance.
    In other words, the article doesn't really system benchmark compare something like:
    DDR-900 (FSB=450, 1:1, tRD=7, tCS=4)
    side-by-side with
    DDR-1000 (FSB=500, 1:1, tRD=7, tCS=4)

    I do understand, now what to aim for when OC'ing my system with regard to what will yield best DRAM performance, but still am a but foggy on when sacrificing a low tRD setting, for gains in FSB (and CPU speed) will pay-off, with regard to overall system performance? The general concensus I get here is "CPU is King" and if that means raising tRD a few notches to achive stability with higher FSB setttings, then so be it.

    But, I am left with a question from the article:
    I'm working on a 9.0x450@2.00D config, and have achieved stability with: tRD=8, tCL=4, vMCH=1.24, vDRAM=2.14. If I wanted to try and get tRD=7 (leavign all other settings the same...), what is standing in my way? vMCH only? I'd be comfortable raising vMCH up to ~1.32-1.34 or so, if that is all that would be needed. Or are there other factors?
    Last edited by corlay; 07-17-2009 at 01:31 AM.
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  3. #13

    Default Re: tREAD and CAS Latency?

    I can't reach tRD of 7 @400-460FSB with 2D/2B multi and tCL=4 on my UD3P board regardless of the MCH Core. I can reach tRD of 7 by either dropping the tCL to 3, or use the 2.5A/2.66D/3A multi with tCL=5.
    QX9650 batch L739A761/ GA-EP45-UD3P/ Kingston KHX9200 4x1G

  4. #14
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    Default Re: tREAD and CAS Latency?

    Quote Originally Posted by gampamu View Post
    I can't reach tRD of 7 @400-460FSB with 2D/2B multi and tCL=4 on my UD3P board regardless of the MCH Core.
    NEITHER CAN I!!!!

    that's sort of my point.
    The article starts out by making the disclaimer that nothing they print is verified to result in stability, then they go on to set the bar ridiculously low for tRD and TRD, and finally tell you that if you're not within these optimal ranges you've not OC'ed your system effectively or efficiently.

    I can reach tRD of 7 by either dropping the tCL to 3, or use the 2.5A/2.66D/3A multi with tCL=5.
    Stable at tCL=3? That's impressive....
    case: Gigabyte 'Triton 180'
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  5. #15

    Default Re: tREAD and CAS Latency?

    Quote Originally Posted by corlay View Post
    ...
    The article starts out by making the disclaimer that nothing they print is verified to result in stability, then they go on to set the bar ridiculously low for tRD and TRD, and finally tell you that if you're not within these optimal ranges you've not OC'ed your system effectively or efficiently....
    In defense of the author of the article, the write up was on ASUS ROG Rampage Formula. The author makes no claims in the article the info provided applies to any other boards or chipsets. I can say from experience, the lowest tRD setting achievable does seem to depend on the chipset. I was able to run tRD=7 at 400-450FSB, 1:1 divider, and tCL=4 with a couple of Gigabyte P35 boards using the same memory. Although I have to settle for 1 higher setting with the P45, I like the P45 better. I can reach higher FSB and CPU clocks on the P45 and that's much more important than one notch difference in the tRD.

    Quote Originally Posted by corlay View Post
    ...Stable at tCL=3? That's impressive....
    Yeah, these old 1G D9 sticks rock. They will run up to 800 at 3-4-3-12 , up to 1000 at 4-4-4-12, and 1200+ at 5-5-5-15. Too bad they are no longer made. Currently running at 459FSB, 2.66D multi (1224), 5-5-5-15-42 timings with tRD of 7.
    QX9650 batch L739A761/ GA-EP45-UD3P/ Kingston KHX9200 4x1G

  6. #16
    Lsdmeasap's Avatar
    Lsdmeasap is offline GIGABYTE Guru
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    Default Re: tREAD and CAS Latency?

    tRD of 7 on P45 @ 400 FSB+ w/ x.xxD is effectively the same as tRD of 6 on P35 using 400 FSB+ so in all actuality you guys are trying to push to tRD of 6 which isn't going to happen.

    So tRD of 8 is equal to tRD 7 of the past P35/X48 ect boards, this is why things seem so hard for you and old articles do not apply. Things have been changed in the chipset, I mentioned something along these lines in the Crucial memory Review thread I made (See Sig)

    So for normal users having stable tRD of 8 @ 400+ FSB is great, and about all you can expect to get without going overly extreme with the voltages or super loose on the timings which would negate the idea.

  7. #17
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    Default Re: tREAD and CAS Latency?

    All you have to do is play with the settings and find out wich one works for you the best.
    In my particular case, with FSB 333 I was able to use a tRD of 6 with the 3.20B multi.
    After increasing FSB to 400 nothing lower than tRD 8 would POST. Untill I gave that article a thorough read, and began understanding how things work. After increasing MCH to 1.22V I was able to use 2.66C multi and a tRD of 7.
    Just for the fun of it, I thought why not try to see if I can get a tRD of 6. So I upped the MCH to 1.28 and was able to POST with tRD 6. Still, that was not stable during prime testing. So I gave MCH another bump to 1.32V and I was running 400 FSB, 2.66C multi and tRD 6 with 5-5-5-15 and as low as 2V for the RAM.
    Experiment with the BIOS, and find out wich settings are the best for you.
    Last edited by morph; 07-17-2009 at 05:16 PM.
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  8. #18
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    Default Re: tREAD and CAS Latency?

    Quote Originally Posted by Lsdmeasap View Post
    about all you can expect to get without going overly extreme with the voltages
    Interesting.

    I have a question:
    I'm currently stable with: 9.0x450@2.00D, tRD=8, tCS=4 (4-5-5-15) (4-4-6-54-4-2); vMCH=1.26, vDRAM=2.16

    I have quite a bit of "safe" voltage range to apply to the vDRAM (mfgr spec. voltage range = 2.10-2.30), *if* that would help me run tighter timings? Currently, running DDR-900 is technically an underclock for this kit. But 4x2gb always presents an additional hurdle to clear.

    Might I be able to get my Standard timings back down to 4-4-4-12 with more vDRAM? I don't mind adding significant voltage there because I'm well within spec; as long as there is a benefit, and it doesn't impact my other voltage settings too much. I just wasn't sure if vDRAM is the key to lower DRAM timings? or if other settings like vMCH come into play?

    Last night, I tried to get to 9.0x463@2.00D; but pretty much determined that I'd need a Vcc > 1.3625v to get there (initial testing revealed that a minimum of 1.375v was required for any amount of stability....). So, I think that I'm going to stay with 9.0x450@2.00D; and try to optimize and tighten things down as much as possible.

    BTW, I compared my 9.5x422@2.00D, tRD=8, 4-4-4-12 and 9.0x450@2.00D, tRD=8, 4-5-5-15 configs in a few benchmarks last evening, and the FSB450 config performed about 4% better overall...
    Last edited by corlay; 07-20-2009 at 10:20 PM.
    case: Gigabyte 'Triton 180'
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  9. #19
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    Default Re: tREAD and CAS Latency?

    spent some time over the weekend trying to get my memory timings and/or tRD lower; and I seem to have hit the absolute wall.

    I started by going for 4-4-4-12 Primary Timings, tRD=8, and danced all around my stable 4-5-5-15, tRD=8 settings by adding Vtt, vMCH, vDRAM and testing with 0, -1, -2, & -3 MCH Ref's (MCH ref values indicate how many "tics' below the default of 0.760 @ Vtt=1.20)

    I tried Vtt=1.24-1.28, vMCH=1.26-1.32, MCH Ref = 0,-1,-2,-3, and vDRAm=2.16-2.28; testing just about every possible combination. Most scenarios would fail in the first 5min., so it wasn't too time consuming. Any combination with vMCH >1.28 would fail almost immediately. As would Vtt on either side of 1.26. I also tried manually setting Drifing Stregth Profiles, and that didn't yield any better results. It seems that once you near the absolute edge, settings in combination get much less forgiving - you really need to nail an exact combination.

    The best combo of settings I could find was: Vcc=1.3375, Vtt=1.26, vMCH=1.28v, MCH Ref=-3, vDRAm=2.18v; and this only yielded ~1hr. of stability in p95 blended. Only one other test came this close, and was identical except for vDRAM=2.26.

    I finally conceded that it just may not be possible to reach my reduced timings goal, so I backed-off the Primary Timings to 4-5-5-13, keeping all other settings the same; and it was running strong in p95 blended @ the 8hr. mark this morning. If it's still good tonight, I may try and get 4-5-4-13 or 4-4-4-13. But 4-4-4-12 seems like it's not possible.
    case: Gigabyte 'Triton 180'
    power: Corsair 'HX-620'
    motherboard: Gigabyte 'GA-EP45-UD3P' (rev.1.1, F9)
    cpu: Intel 'e8500' (E0)
    cooling: Xigmatek 'HDT-S1283'
    memory: OCZ 'Reaper' 4x2gb (OCZ2RPR10664GK)
    storage: Western Digital 'Black' (500gb)
    video: EVGA 'GeForce' GTX-260
    display: Samsung 'SyncMaster' 2333sw

  10. #20
    Chike is offline Senior Member
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    Default Re: tREAD and CAS Latency?

    Is it possible to use 450x9@2.40B DDR-1080 5-5-5-18 instead?
    This should give more bandwith with no or minimal increase of latency.

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