Memory running slower than it should?

I have 2x 512MB DDR400 sticks and 2x 256MB DDR333 ones. The 256 ones are the same brand, and can work in Dual-Channel mode. The 512 ones are not the same brand, and don't work in Dual-Channel. Though I've heard that it's not necessary for them to be the same brand, that they only need to be the same speed and size. However, their timings differ a bit too. Another problem with the 512 ones is that when paired together, the motherboard automatically decreases their speed to 266MHz. Forcing 400MHz mode in the BIOS doesn't help. There is no such problem with the 256MB ones, they always stay at their 333MHz. I tried running only one 512MB stick at a time, and it worked at 400MHz so they're not counterfeited or something. Right now I have all of them running but the motherboard has further decreased the speed down to 200MHz.

Is it possible to achieve Dual-Channel 400MHz mode with 2x 512MB sticks of different brands?

Which is better: 1.5GB 200MHz Single-Channel, 1GB 266MHz Single-Channel, or 512MB 333MHz Dual-Channel (which is 666MHz effective I understand?...)

Please help and thanks for your time.

What board do you have?

ASRock P4V88, yeah not the best, but reliable. I fixed the 100MHz problem. Now my 1.5GB RAM runs at 133MHz, it can't do more, it's 4 sticks. But why do they still run at 133MHz when I only use 2x 512MB sticks? Shouldn't it be able to do 200, or at least 166?...

It should be completely capable of running all 4 sticks at 200MHz in dual channel..

What happens if you set it all to auto? Or try and force 200MHz?

In theory the PT880 supports up to 8GB at DDR400 in dual channel. Your board shouldn't be any different...

Well the 256MB ones are DDR333 so if you are right, it should run all 4 sticks at 166MHz.

Forcing 166 or setting it to Auto still reverts to 133, although it says 166 in the BIOS. Everest and CPU-Z say 133. The 512MB ones should work well at 200 though, same speed as my FSB...

I'm using the newest BIOS. I don't know, should I try an older version? My floppy drive is broken I think. I'll have to look into that too...

Also I found another problem. When using all 4 sticks at once I might get errors in some applications. Noticed it today when playing Team Fortress 2. I kept receiving error messages after a few minutes of playing, and my game files would be corrupted. I reinstalled them, tried to play, and same thing happened. Reinstalled again, took out the 256MB sticks and it works alright now. But it's only 1GB, I kinda like 1.5 more...

set the timings on the ram modules manually, find what are teh highest values for the memory timings on the memory sticks and failing that, simply input the highest your board can take - but usually 4-4-4-8 works. then try forcing 166 mhz. also, try forcing the voltage to the voltage specified by the memory modules if you can - iirc its 2.65 volts or whereabouts.

I can only change the CAS latency, highest is 3.

About the voltage, there is only one option called DRAM Voltage, I can choose betweem Normal and High. Is that what I need?

Also I have no idea what these next options do: DRAM Driving for ODT, V-Link Speed, On-Die Termination.

OK I just tried using higher voltage and I still get 133MHz. I am now running on 2x 512MB DDR400 sticks. Took out the 2x 256 ones because there were errors. What if I tried using higher voltage with 1.5GB? Would I still be getting errors?

set cas latency to 3
set DRAM voltage to High.
Check if you can update bios - that will probably solve problems if there is a newer one

I already have the newest BIOS. I tried 3 CAS latency and High DRAM Voltage with 1GB and it didn't help. Probably won't help with 1.5 too.

at this point, all you can do is memtest each individual stick of ram and see if there is one that is dead or not.

it might also be worth reading the manual to see what the settings you mentioned earlier are for (DRAM Driving for ODT, V-Link Speed, On-Die Termination.)

i know my friend's board had an option for ram compatibility - had problems runing mixed ram until i enabled it. check to see if you have such an option.

Yes, I do have such an option, but it lowers RAM speed to 100MHz? Is it worth it? 133MHz 1GB vs 100Mhz 1.5GB?

when you enable that option, do you atleast get 1.5 gb dual channel?

and worst comes to worst, you can try overclocking the entire system to get back a couple mhz.