Memory Timings

Hiyas...

Using Corsair TwinX1024-4000Pro with an Abit IC7-MAX3 mobo I was wondering what timings I should use or leave at default settings of 800FSB at 1.1 (seem to be mobo defaults).

Yes I'm cheating abit (pun intended) by asking this question and I have spent time reading the forums. Seems understanding the memory is what i'm having trouble with.

Thanks,
Scratches

if you are only running the default clock rate you should be able to run a lot faster timings that what they are rated for. If you clock the machine up some the rated timings are likely to be about right. You just have to try and see which values work best, very few people have this ram and board yet, and no one has the particular examples you have.

Thanks for the reply but I have no idea what the settings mean. Like the 2-2-2-5 in your sig.

Yep... killer n00b here.

Thanks,
Scratches

Those are the individual memory latency values. Your bios will have places to set them under the "advanced chipset" tab. They are supposed to be detected by the machine's bios from the eeprom chip on the memory module (the "spd") at default values.

They can be manually reduced to allow greater performance or increased to allow higher clock rates by lessening the strain on the memory. They are generally referred to as "cas" timings, as the first one is the cas latency settting. It has the most dominant effect on memory performance of the four, although we generally strive to minimize all of them to make the most of our memory's performance.

To run anything like PC4000 speeds (500MHz) you will have to run high values for these, like 3-4-4-8. This offsets a great deal of the advantage of running the memory this fast as compared to running the ram at a slower rate with fast timings like 2-2-2-5.

If you are running your machine at the default 200/800fsb with the 1:1 mode, you are running the memory at 200MHz also, which acts like 400MHz due to the nature of DDR. The fsb of a P4 transfers four units of data per clock cycle, and is referred to as a "800MHz" bus, but in reality is only running at 200MHz. Likewise the memory (being DualDataRate) transfers two units of data per clock cycle, so DDR running at 200MHz is said to be "400MHz DDR".

The smart way to get the ram speed up is to increase your default 200fsb to 250MHz, bringing the the ram up to 500MHz at the same time (1:1). I don't know what cpu you have, but if it is a 2.4C it would run at 3GHz from the increase of fsb to 250, a 2.6C would run at 3250, a 2.8C at 3500, etc... The 2.4C is almost certain to run at the 3000MHz 250fsb dictates, but you may have to increase cpu voltage and/or stop short of 250MHz fsb due to the varying quality of individual cpu's. Or you might get lucky and even a 2.8C go all the way to 3500 with stock cpu voltage. You never know till you try.

In any event leave the memory timings slow (3-4-4-8) until you know how much fsb your cpu will allow, than reduce them as much as possible before the machine acts up.

Wow thanks for all that info. Printing it out so i can play with bios and read it. Running a 2.4c i can take it to 250, boot and play with it with no problems. At 251 winxp pro bluescreens during boot no matter how much volt i throw at it. Not sure if this is due to the cpu cutting out above 250 or i need to adjust some more timings to go above 250.

Thanks,
Scratches

Sounds to me like your memory's MIA above 500MHz. This is not surprising, the fact that it is stable at 250 is. Even though the ram technically supports it you never know it's going to work until you try it. 500Mhz on the ram on modest voltage is pretty rare.

That brings up the other important topic, voltage. Both CPU and memory may work better at higher operating voltages. The cpu should be default at 1.525V, I'd up that to 1.6V for testing. I'd set the memory voltage to 2.8 or 2.9V, I don't know if the 3V+ settings work on the Max, you'll just have to try them. Anything up to 3.1V is safe on the ram and will allow greater clock speeds and tighter tiimings at the same time.

Also update your bios to the latest version (if not already current) and try setting the GAT settings like this : Auto. Auto, Auto, Disabled, Disabled. These are chipset level settings that effect the achieved latency of the memery subsystem as a whole. Later after you get your FSB maximized try setting the first one to "Turbo" and test for stability.

Seems anytime i change the settings to something other then 1:1 I get just loud beeping during boot up and thats it. Same thing goes for when i change any of the GAT settings away from auto. Anyone think maybe my memory is shot? System runs stable the way it is though.

Thanks,
Scratches