Dual channel - mixing ram ?

[madwelshboy]

Hi guys,

I currently have 1gb of Geil PC4000 (2x512) running in DC, I am thinking of getting another 512kb (2x256) (a friend has offered to me for £80). Also think this will help Doom3 too. What I need to know is if I keep the 2x512's on 1 memory channel and put the 2x256's on the other, will it still run in Dual channel?
Also will I see a performance difference? I dont overclock my memory too much (crappy volt on IC7).
Thanks guys.

[Nomadd]

I thought they had to be the same type? Normally you can get away with 'unmatched' pairs (i.e. two sticks of the same type of RAM that weren't sold as a 'dual channel pack' - that's what I've done, and run DC no problem), but I don't think two 512 and two 256 will work in DC mode. Check your mobo manual for details.

You'll also find that more sticks of RAM (i.e. going from 2 to 4 sticks) usually ends up limiting your overclocking, rather than helping it. Depending on how for you are currently pushing, you *may* even have to back things off.

As it's a mate, I'd suggest getting the RAM of him and testing it. If it doesn't do what you want, hand it back.

Oh, and I with 1GB already, the extra 512 isn't going to help in Doom3.

Nomadd

[Agent]

They dont have to be the same brand.
They dont have to be the same size.
They will work fine.

Nomadd is correct in that it may hinder your overclocking though.

[Flash]

They dont have to be the same brand.
They dont have to be the same size.
They will work fine.

Nomadd is correct in that it may hinder your overclocking though.

if you had a £1 for everytime you said that youd be able to buy out Qtec and get decent PSUs made

[Nomadd]

Yep. checked: http://static.tigerdirect.com/pdf/Abit_IC7-G_Manual.pdf

Section 2-3 states that as long as you use the same 'types and sizes' in slots 1-3 and 2-4, they can be different. That is the only case when you can mix types/sizes.

Nomadd

[Agent]

if you had a £1 for everytime you said that youd be able to buy out Qtec and get decent PSUs made

Very true

Yep. checked: http://static.tigerdirect.com/pdf/Abit_IC7-G_Manual.pdf

Section 2-3 states that as long as you use the same 'types and sizes' in slots 1-3 and 2-4, they can be different. That is the only case when you can mix types/sizes.

Nomadd

Ive spoke directly with some of Abits technical staff, and i can assure you, they dont need to be the same size or brand, even under those conditions. You wont get the full 128bit addressing across the RAM, but it will be in dual DDR mode.
All dual DDR mode is, is having the RAM opperating on different memory controlers. Considering these are physicaly attached to the PCB tracks to the RAM, unless the board can re-solder itself, they will be using different controlers, hence dual DDR.
They are probably writing that, because like i said, you will only get parcial 128bit addressing, while the rest is addressed as 64bit. There is a debate if this is "true" dual DDR, but at the end of the day, it works, and you get an increase from it - thats good enough for me.
Aslong as people realise that you will get a better result if they are the same size, but it will acctually work with different sizes without a huge difference, its all good imo

On the other hand, some people like to argue that unless all the RAM is being addressed as 128bit, then its not using "true" dual DDR. While i can see their point, you are getting some advantage from it.
Abit updated their BIOS's to now show that the system is runing in dual DDR mode provided they are just on different memory controlers, regardless of size. If its good enough for Abit, its good enough for me too

[Zak33]

if ya want I can come round, and fry your BIOS and then you wont have to wrry about it

Seriously tho....from a pure logistics thought train....surely a 512 and a 256 on each channel would be common sense.

However....with MY reputation, run away from any advice I may give.

[Rave]

Yeah, the best solution is to set it up with 768mb on each channel, even if it works with 1GB on one and 512MB on the other.

I seem to recall that Lost Circuits found that the 875 chipset automatically backs off some timings if you go from two to four sticks of RAM- if so, you may actually see a slight performance decrease. Unless you really do need more than 1GB of RAM I wouldn't bother doing this- Doom 3 shouldn't need more than 1GB.

Rich :¬)

[Zak33]

oooh, in Il2 more ram at a slower speed would be a worthy thing.

I've tried and as good as dual mem is on my nforce2's to have a bit more, even if its slightly slower is normally a good thing.