Memory Clock Index Value, what happens above 400MHz?

I am running (when they are back from RMA) a set of TwinXMS DDR 500 DIMMs in an ASUS A8N5X. My CPU tops out at 233MHx, above that is not stable. The max multiplier I can run is 10X so with the memory set at 400MHZ in the BIOS( a 1:1 ratio) and the CPU clock at 233, I can get the RAM running at 233. There is a setting in my BIOS I have not seen referred to in any overclocking FAQ and I am wondering if this might be a way to increase the speed of my RAM, given that I am not even up to stock speeds much less any of the overclocking for which it is famous.

The setting is in the Manual RAM settings and it is called the Memory Clock Index Value. It is callibrated from 200MHz to 600MHz and the Auto setting is at 400 with the next step up being 433. All the guides I see for overclocking stop at 400 so I am not sure what will happen above that point.

Much thanks

Wait... what's the HT multi at? And the voltages?

The CPU voltage is at 1.35 as moving it up does no good. It still tops out at 233. The RAM will be at 2.75. The HTT muliplier is 4X as 5X would move it above 1000. I only want to raise the RAM speed and I had not seen a RAM Frequency Ratio Divisor more that 1:1 mentioned before.

What are your system specs?

ASUS A8N5X, AMD 3200+, Corsair TwinXMS DDR 500.

No one knows what the settings above 400MHz would do??

I dont see how setting your ram faster than your cpu would do any good because the CPU can only give it X ammount of data...if your ram is running at X+2...sure it would be running faster but would not give any benefit...

yeah, generally it's better to run your cpu and ram synchronous (or at least usually prefered). you may have simply bought too much speed in the ram if you can't push that fsb that high. you will end up running into a wall with the cpu or nb most likely. maybe with some REALLY good cooling, but other than that, you have prolly just hit that wall.

if you can change the multiplier, simply try running with a lower multi to see if you can get the higher fsb. if you can lower it, try lowering it significantly (down to like 6-7) and see if you can pump up the fsb with the 1:1 ratio. get that as high as you can with stability, then try pumping that multiplier back up. like i said though, it may take considerable voltage, so you prolly want really good cooling.

But what is the effect of setting the Memory Clock Index Value higher than 400. I know the divisors are at 5/6 for 333 and at 1:1 for 400 but what happens at 433? Does the divisor now become a multiplier for the RAM? Is it ignored? Does it mess with the CPU multiplier? Why is there nothing above 400 in any of the FAQs and calculators?

if i could get the freakin manual to download, i could possibly help with an idea as to how to work with this. as far that particular setting, i have never seen anything with that particular idea in a bios before. usually you pick a cpu clock to ram clock ratio (4:5, 5:6, 1:1, etc...) and then it just goes off the fab like that. this i am not too sure of, but i will let you know if i figure something out.

hell, part of it is that i am just curious now, haha

okay, i think that i have found some answers for you. from what i am seeing, it looks like you want to do something like this:

1) drop your multiplier first, this will allow you headroom for playing with the overall clock

2) i believe that the setting you are inquiring about does effect the ratio, but most are run better at 1:1 anyway. but it looks like the high you make that setting, a higher ratio it chooses to try to pump the ram speed up. but like i said, it is usually better to run synchronous, so you might be better off leaving it as 200Mhz and trying it this way first.

3) so, take the multiplier down a good ways to give yourself plenty of room to play with the clockspeeds, prolly like 5-6 to give plenty of room so that you make sure you are only stressing the ram speeds and don't have to worry about the CPU.

4) go ahead and take the cpu all the way up to 250 then and try it out. ideally you should get that ram running at 500 (what it's rated) and your CPU should be about 1250-1500, plenty of room to play with. this should boot. then slowly pick up the clock until you hit the wall with the ram. my guess is that you could push around 280 as long as the bus lets you go that high.

5) once you get your ram where you think it tops out (or where you like it) then just start bumping that multiplier back up. it will not go as high as before most likely, but you should be able to get close to the same over all speed i would imagine. my guess you be that you could get the multiplier back to 8 or 8.5 before you start to really push it again and are back where you were with 233x10.


here is the site where i got a good amount of info from on this. it looks like a LOT of help... hell, it helped me even figure out basically how it all works. i haven't played with 63's yet.

http://www.planetamd64.com/index.php?showtopic=12066

good luck and let me know if that helps at all

Thanks for all your work. I have done all that you suggest and that is how I found the top end for my CPU. Given all the info, no one evr mentions setting the RAM divisor above 1:1. Given my system, there is no way to get the RAM above 233 without dropping the CPU by setting the CPU multi lower than 10X. That is just the way the math works out. But nothing ever mentione setting the RAM divisor higher than 1:1, which, in theory, could solve my problem. I just don't want to try it unless someone confirms exactly what is going on.

well, if you lower the multiplier, you should be able to up the clock, as it gives the same results. i could be mistaken, but i don't think that there is necessarily a clock top end, or multiplier top end, but the top end is the combo of the 2. like it looks like you top out at 2300Mhz over all, whether it be 233x10 or something like 280x8. what i am saying is drop the multiplier, but up the clock speed, it would give the same overall cpu speed, but should give you a higher ram clock as well.

you could try raising that index value, but i am not sure how well that will work out, as running synchronous is usually better.

EDIT: one of the things that i saw, but wasn't too sure how it worked, is that you could try lowering the HTT to 3x. that might allow you to get the higher cpu clock speed to get higher ram speed. then just adjust the multiplier to match. just make sure to start with a low multiplier