DDR400 RAM question..

[nina]

First I had two Apacer DDR400 512MB CL2.5-3-3-8
which runned under dual channel at 400 Mhz.

I added this week two Kingston DDR400 1GB CL3-3-3-8, dual channel

Well, now I have a slower pc, it runs under 332 Mhz (2x166)...
instead of 400 Mhz.

My bios is set to 'auto spd'

How do I adjust the bios manually so that everything runs under
400Mhz again?

I notice in CPU-Z that the kingston are set by the spd on CL2.5,
I guess that's the cause of decrease in Mhz.

Is it safe to put everytime on CL3 or would this damage the Apacer's?

[vertigo]

Well somebody told me once that if a module is CL3 @ DDR400, it will be CL2.5 @ 333. The reason for that is 2.5/333 = 3/400. I think the computer is using CL2.5 and at the speed of the slower modules.

You can get them to run at DDR400 at CL3, but it isn't necessarily faster. Google for some info about whether CL3@400 is faster than CL2.5@333. I would choose the one that matches your bus speed. If your cpu runs at 1667, for instance, use the 333.

[vertigo]

One more thing, you can't damage the ram by reducing timings, but if you reduce them beyond what the ram is capable of you will get much less performance. I would just choose between CL3@400 and CL2.5@333.

I suppose you could try 2.5@400 and then benchmark the memory, but why would the memory be rated CL3 if it was capable of 2.5?

[rei]

in this case, it's your cpu, do you have a winchester cpu or mobo that can't run 4 dimms at 400? if not they will downclock to 333.

this is a known limitation of earlier a64 chips and mobos themselves.

[nina]

My MB is an Asus P4PE800SE
with P4 Prescott 3 Ghz
settings are
Bus speed : 800 Mhz FSB 200 Mhz
memory set 2.5-3-3-7 FSB : DRAM 5:4 Freq : 160 Mhz

spd settings :
For Kingston memory 3 options
133Mhz : 2/2/2/6 166 Mhz : 2.5/3/3/7 200Mhz : 3/3/3/8

For Apacer memory only 1 option
200Mhz : 2.5/3/3/8

I guess that the auto spd funtion takes the CL2.5 because
all four RAM modules support this and then takes the lowest
frequenzy of them, which is 166Mhz for CL2.5 on the kingstons

If I remove both apacers I get 400 Mhz
If I remove both kingstons I get also 400Mhz
When I place the four ram modules I get 332 Mhz

So I have to choose between either 2GB ram at 400Mhz
or 3GB ram at 332Mhz, I will search a bit on the net if the change
is big. Not all my project need 3GB RAM, so if I want speed, I'll
remove the apacers.

Thanks for your help!