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Explanation Of Twr, Trfc, Twtr, Trrd, And Trtp Ram Timings


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#1 Kudos

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Posted 16 July 2008 - 06:14 PM

I have a Foxconn X38A motherboard and I finally figured out that my memtest86 and prime95 errors were due to not having the TWR, TRFC, TWTR, TRRD, and TRTP timings set high enough. They were set at 3-64-3-2-3 and I changed them to 4-64-4-3-4 (4-4-4-12 memory). Since then memtest86 and prime95 work perfectly. Does anyone have an explanation of exactly what these timings mean, and where you can find the timings settings for your RAM (I have Geil DDR2 800 RAM). I was also wondering how much these timings affect performance/stability. Any comments are welcome.

Edited by Kudos, 16 July 2008 - 06:17 PM.


#2 hardnrg

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Posted 16 July 2008 - 07:27 PM

I have Geil Ultra 2x1... when I ran it at 4-4-4-12-2T or 4-4-4-12-1T, I found some settings that worked well for the secondary timings on my 680i:

tRRD: 3 (or 4)
tRC: 18 (or higher)
tWR: 5 (or 6)
tWTR: 9 (or 10)
tREF: 7.8us

I can't set tRFC in my BIOS... and I either don't have tRTP (Precharge Time) visible anywhere, or it's called something else

There are various DDR2 overclocking guides floating around that give recommend values and ranges that generally work well... you can read about them in depth to see exactly how they work, but it gets immensely complicated, and it's not actually necessary to fully understand them, just the relations that some have, e.g:

tRC >= tRP + tRAS

some people say tRC >= tRP + tRAS + 2... and I find this is more stable when really pushing the clock speed

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#3 Syngensmyth

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Posted 16 July 2008 - 09:13 PM

tRC >= tRP + tRAS

some people say tRC >= tRP + tRAS + 2... and I find this is more stable when really pushing the clock speed

This would be interesting but my Googles are not finding the above info. Any links handy available?
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#4 hardnrg

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Posted 16 July 2008 - 09:22 PM

nope... but if you google: ddr2 overclocking guide, several clicks later you should find something :)

or: ddr2 overclocking tcl trp trcd tras trc

etc

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#5 Praz

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Posted 17 July 2008 - 05:44 AM

A friend has an explanation posted of all the timings you asked about.

Timing Explanations

#6 Syngensmyth

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Posted 17 July 2008 - 07:43 AM

Praz, thanks. That is exactly what I'm looking for. I've never seen it so well put.
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#7 Kudos

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Posted 17 July 2008 - 10:26 AM

Wow thanks guys this was very helpful. :thumbs-up: One problem I'm having is that there does not seem to be a selection for the command rate (e.g. 1T, 2T etc) in my BIOS. I'm guessing my RAM is at 2T though.

Edited by Kudos, 17 July 2008 - 10:29 AM.


#8 Praz

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Posted 17 July 2008 - 10:40 AM

Quite a few Intel DDR2 based boards have no manual manipulation available for Command Rate. When the option is unavailable the chipset defaults to 2N. It requires a strong chipset and good memory to run much over 900MHz at 1N.

#9 Syngensmyth

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Posted 17 July 2008 - 02:44 PM

cpuz and other programs will let you know if 1 or 2t. BIOS screen, memtest86 ... others.
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#10 dr_bowtie

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Posted 17 July 2008 - 06:37 PM

I have also found that tfrc will change trc on AMD boards...so it must be related somehow...

not sure is changing trc will effect trfc though...I havent seen were trfc is as big an issue on Intel as it is on AM2 boards with Brisbane CPUs...
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#11 Waco

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Posted 17 July 2008 - 06:51 PM

Practical definitions are worth a lot more than the actual technical definitions. If you really want to play with the more advanced timings you usually have to look up the spec-sheets of whatever modules are used on the memory you're running.

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#12 Kudos

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Posted 18 July 2008 - 11:13 AM

Practical definitions are worth a lot more than the actual technical definitions. If you really want to play with the more advanced timings you usually have to look up the spec-sheets of whatever modules are used on the memory you're running.

I would love to know where I could find that info on Geil RAM. Geil's website is not that great and I can find no actual spec sheets for my RAM.