very good explanation here on RAM timings...
RAM Timings/options
Key
*Star= slight influence Bandwith
**Star= Very influential Bandwith
star*= Slight influence stablity
Star**= Very influential Stabilty
*star*= Sligth influence in both stabilty and bandwith
**Star**= Very infuential in both stability and Bandwith
DRAM Timings
**Dram Frequency Set(Mhz)**= 100(Mhz)(1/02), 120(Mhz)(3/05), 133(Mhz)(2/03), 140(Mhz)(7/10), 150(Mhz)(3/04), 166(Mhz)(5/06), 180(Mhz)(9/10), 200(Mhz)(1/01).
This option sets the Dram ratio. with a64, the ratios are not always writen in stone, for example 166(5/06) isnt always 5/6 ratio. you can refer to this chart for the exact ratios(they may not all be right, and thanks to Oskar_WU for his help with the chart)
**Command Per Clock(CPC)**= Auto, Enable(1T), Disable(2T), this is also called Command rate.
It is best, in most cases to use Disable(2T) with 2x1gig, 2x512, or 1x1gig Ram modules for the best stablility. 1T yeilds better performance, and 2T usually yeilds the best stabilty/overclock
PLEASE NOTE THAT IF YOU ARE USING A "CO" REV. CPU THIS OPTION(CPC) WILL NOT APPEAR IN BIOS. THIS IS BECAUSE "CO" REV. CPU'S DO NOT SUPPORT 2T TIMING, ONLY 1T. IF YOU HAVE A "CG" REV. CPU, YOU WILL BE ABLE TO SELECT EITHER AUTO, 1T, OR 2T.
*Cas Latency Control(tCL)**= 1, 1.5, 2, 2.5 3, 3.5, 4, 4.5. I would suggest only using, 2, 2.5, and 3..
This is the first timing that most ram companies rate there ram with. For example, you might see ram rated at 3-4-4-8@275mhz. this is the 3, in than situation.
2 yeilds the best performance, but, unless you have either Winbond BH-5, or BH-6, it is unlikely you will beable to reach you maximum overclock at CAS2. CAS3 is usually yeilds the best stablility/overclock.
PLEASE NOTE, IF YOU HAVE WB-BH-5/6, YOU MOST LIKELY WILL NOT BE ABLE TO USE CAS3, AND SOME MAY NOT BE ABLE TO USE CAS2.5, MY BH-6 WILL NOT POST AT CAS2.5, OR CAS3, IT WILL ONLY POST AT CAS2.
**RAS# to CAS# delay(tRCD)**= 0, 1, 2, 3, 4, 5, 6, 7. I would suggest only using 2-5
This is the second timing that most ram companies rate there ram with. For example, you might see ram rated at 3-4-4-8@275mhz. this is the 4, in than situation.
2 yeilds the best performance, and 4-5(5 is usually overkill) yeilds the best overclock. Most rams will not be able to use 2, and reach there max OC.
*Min RAS# active timing(tRAS)*= 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15.
This is the forth timing that most ram companies rate there ram with. For example, you might see ram rated at 3-4-4-8@275mhz. this is the 8, in than situation.
This is a very debated timing. Some may argue that 00, 05, or 10 is the faster/most stable. but i really think there isnt a right anwser for this one, it all depends on your ram. But, if you need a good starting point, usually most/all rams can accieve there max OC on 10 tRAS, even if one of the other setting is faster.
**Row Precharge timing(tRP)**= 0,1, 2, 3, 4, 5, 6, 7. I would suggest using only 2-5.
This is the third timing that most ram companies rate there ram with. For example, you might see ram rated at 3-4-4-8@275mhz. this is the 4, in than situation.
2 yeilds the best performance, and 4-5(5 is usually overkill) yeilds the best overclock. Most rams will not be able to use 2, and reach there max OC
**Row Cycle Time(tRC)**= 7-22 in 1.0 increments.
7 yeilds the best performance, 15-17(i think 17 is overkill) yeilds the best stability/overclock. i would start at 15, and work your way down from there. Also, 7 is usually much to tight, for most ram.
**Row Refresh cyc time(tRFC)**= 9-24 in 1.0 increments.
this timing is usually always set to 2-4 clocks higher that the tRC.
10 yields the best performance(well 9 would, but 9 is to tight), and 17-19(i think 19 is overkill) yields the best stabiltiy/overclock. i i would start at 17 and work your way down
*Row to Row Delay(also called Ras to Ras delay)(tRRD)*= 0-7 in 1.0 increments.
00, or 2 seems to yields the best performance, and 4-6 yeilds the best stabiltity/overclock. i know that 00 sounds odd, but it works great for me, even at 260mhz
*Write Recovery Time(tWR)*= 2, 3
2 yeilds better perfomance, and 3 yields better stability/overclock.
*Write to read Delay(tWTR)*= 1, 2.
1 yeilds better perfomance, and 2 yields better stability/overclock.
*Read to Write delay(tRTW)*= 1-8 in 1.0 increments.
1 yeilds better perfomance, and 4(i think any above 4 is overkill) yields better stability/overclock.
*www.ocforums.com/showthread.php?t=329627
Another thing I noticed, My 256MB ram is PC2100 DDR-266 and my 512MB ram is PC3200 DDR-400. Both are J chips. Yet they are both using the same timings (the J's and D43). The bandwidth difference is almost double. The J's are not even specied ot run @ 400MZH. But the D43 DDR-400 are run @ 3-3-3. IE The J's are not designed to run @ CL3 only the D43's are. I suspect they are overclocking the chips. But these was sealed packages from Simmtronics USA.
*www.hynix.com/datasheet/eng/dram/details/dram_02_HY5DU56822AT.jsp
