ASUS ROG Rampage Formula: Why we were wrong about the Intel X48
by Kris Boughton on January 25, 2008 4:30 AM EST- Posted in
- Motherboards
The Rules of Working with tRD: What's Allowed and What Isn't
We mentioned earlier that there are a few rules pertaining to the modification of the default tRD value for a particular memory subsystem configuration. These rules are actually more of a set of equations that we have derived in order to assist the user in pre-determining whether or not a system will POST and operate given the settings in question. They can also be used to explain after the fact why certain configurations refuse to function.
In actuality, there is only one requirement that must be satisfied when setting tRD: The MCH must have a minimum amount of time to complete the clock crossing procedure for each data bit translated from one clocking domain to the other. We have shown the equation below for those that care to know. Unfortunately it does not lend itself well to being solved as the input variables ("t0" and "tckxss") are not readily obtainable.
"t0" is the total time it takes data being returned to the CPU as read in memory to cross from the memory bus domain to the system data bus domain. This is dependent on a number of variables, including memory burst length (4 or 8 cycles), Command Rate (1N or 2N), the memory divider in use, CAS (tCL) timing, and the current FSB. "tckxss" is a little more esoteric in nature and is outside the scope of this discussion; the value is generally very small when compared to "t0". The difference in these times, rounded to the lowest integer plus one, bounds the lowest potential tRD setting necessary for data to be properly transferred from one bus to the other.
Because the first expression is too difficult to warrant everyday use, we spent many hours populating a large test matrix table created for recording the POST (Power On Self Test) results of every strap/divider/FSB/CAS setting combination that our test bench was physically capable of supporting. Using this data, we then developed the method and equation you see above, which can determine whether or not a desired memory subsystem configuration will work. It is possible, and rather probable, that there is another step discontinuity in the logic for FSB speeds in excess of the high value in our test range (466MHz). We will leave the discovery of some such value up to others - unless Intel is kind enough to send us additional 45nm dual-core processors, in which case further testing on our part might be justified.
Entering arguments for the use of the "POST Test Equation" are as follows: tRD, in clocks; tCL (CAS), in clocks; FSB, in megahertz (MHz); N, the memory divider in use, expressed in fractional form (i.e. 3:2 would be 3/2); and "x", which should be chosen from the options provided, depending on the FSB in use. Evaluate the left and right side of the equation separately. The expression is satisfied if the left (actual margin) is greater than but not equal to the right (the minimum required margin).
There are no units purposefully associated with these numbers, as this equation is intended as nothing more than a test to determine whether a system will POST using the desired parameters. If the expression is false, the configuration/system will fail to boot; if it is true then the configuration is allowed and the POST event should at least occur. Keep in mind that this equation provides absolutely no assurance that the system will be stable at the settings provided - just because you want to run your memory at DDR2-1200 CAS 3 and the equation says this is possible, does not mean that your wish will be fulfilled. Let's go through a quick exercise of what we have learned regarding the proper use of the "POST Test Equation" with a few practical examples.
If you can follow these examples then you are ready to move on to the next step - determining optimal system performance points and then validating your results. There are many choices when it comes to deciding how to configure a system for the best possible experience. Some choices are clearly better while other decisions may come to down to personal preference. For instance, some users may be willing to subject their expensive hardware components to higher voltages, creating an environment of accelerated wear and earlier failure. Others may be far less concerned with the consequences of their choices; in either case the trade-offs will be clear. We will now take what we have learned and provide our rationale for why we would feel one overclocking approach to be superior to another. After all, overclocking should always be based on an intelligent decision making process and not the clumsy application of brute-force.
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DragonStefan - Tuesday, June 9, 2009 - link
Hello all.I have:
- motherboard: ASUS Rampage Formula (Intel X48) (logical) and
- Corsair XMS2 Dominator Series 2x2048MB Kit PC2-8500 CL5-5-5-15 (TWIN2X4096-8500C5D)
Should i go for the following setup in bios:
FSB: 400
tRD: 5
Trd: 12,5
Divider: 3:2
tCL: 5
VDDR: High
Allowed: Yes.
Or should i go for a different setup?
If i understand correctly, this is possible..
What do i forget?
I made the calculation, and the answer of the Question if it is possible Yes or No, is 1,67 > 1,33. 1,67 is higher than 1,33. So yes..
Greets From DS
danderson00 - Thursday, October 23, 2008 - link
Hi,I realise this article is quite old now, but found it very useful for tuning my Rampage Formula. Have achieved significantly increased memory performance from this setting. The board seems to configure them fairly well on the auto setting, but there are some cases where manually tweaking them can give a good performance boost.
I am curious about one thing - I would have thought that running a 1:1 divider would allow the lowest tRD value as the two clocks are running at the same speed. Data should be able to be passed between the two buses without delay, whereas if the memory clock is running faster, it might need the delay to prevent 'overlapping' with the previous data transfer. However, according to the formula (and indeed a couple of quick tests confirm it), a 1:1 divider is actually the worst for tRD, the wider the ratio the better.
Any ideas why this is?
Great article anyways!
Dale
Maxxxx - Sunday, June 14, 2009 - link
Yes, you are right about 1:1 divider and tRD. This article incorrectly describes work of the memory controller.geok1ng - Sunday, August 3, 2008 - link
I have a P5WDH a 975X mobo. if i am understand correctly this chipset would apply the TRD from the basic table and my best options would be a Trd of 6 or 8? Is there any way of knowing what Trd number is being applyed? I am running an E4300 at 9x329Mhz and 4 1GB sticks of DDR1100 at 987Mhz Cas 5/6/6/18/21. everest gave me a memo latency of 55.5ns ( better than quite a few 45nm/P35 owners here). Any use going for the Trd 6 option (8:5 divider i believe) since neither my my mobo can reach FSB above 1333 nor my memo can go above 1000mhz and keeping CAS 5 ( it is rated at cas 5/7/7/25/32 but the P5WDH just cant go above 5/6/6/6/18/21). Using a 8:5 divider bellow 1000Mhz memory mean runing the CPU at 2,7Ghz...and using crazy DDR/MCH voltages.Sarsbaby - Wednesday, July 16, 2008 - link
Wow, I just learned alot, I think.Very nice article! Well written and presented.
I'll definately have to clear my CMOS for this one.
jamstan - Friday, July 11, 2008 - link
I would have liked a review of the board itself instead of page after page about clocking. I have this board ready to build my rig today with 2 4870s in CF and I would have liked to read about the crossfire setup, the sound card, etc instead of page after page about clocking. Althou informative I feel the review should have remained focused on the board itself and the clocking crap should have been in a different article. It's a nice feature on this board but its like doing a review of a Corvette and wasting the whole review on its transmission.Sarsbaby - Wednesday, July 16, 2008 - link
You know, this is only one of many reviews for this board, and only one of many on this forum.Try some more searching, and maybe educate yourself more before calling most of this article "Crap". This is probably one of the most useful articles on this motherboard I have found.
With all these new options open to ROG owners, i'm glad someone is taking the time to explain what they mean and why we have paid for them.
And have you ever re-built a transmision? Or tuned an LSD? It's alot more complicated than you think apparently.
DEFLORATOR - Tuesday, May 27, 2008 - link
Why does the author says that the board revision is 1.03G while it is clearly seen on the photoes that it's 1.00G (imprinted between PCIe slots)? Please owners of the board confirm that 1.00G is the latest revision of Rampage Formula (gonna order that tomorrow)viqarqadir2 - Monday, April 21, 2008 - link
HelloI am very new to this stuff and havent been able to make a lot of sense of the configurations despite reading the article several times.
I have the following setup:
Intel Q6600@2.4 Ghertz
Kingston Ram 8500 (5.5.15) 1X4 Gigs - 1066Mh
XFX Geforce 8800GTX XXX edition. (I guess this doesnt matter)
What sort of configuration should I apply?
I also wanted to know if someone has had problems with the MB temperature and whether 51 Centigrades after playing STALKER for about one hour is normal. Any help will be appreciated.
viqarqadir2 - Thursday, April 24, 2008 - link
hmm...I dont know if I've done something wrong but for some reason, 3dMark is showing the memory at 1.9 Ghertz. It's a DDR2 rated at 1066 and I am running it at (according to my calculation) 1000.
The pc feels ridiculously fast. All MB lights are green. The 3d Mark app is giving a score of about 11000. I am not a techie but is it possible that I have discovered something? Is there a way to post screenshots in the comments area?