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dual channel, DDR, same thing?

S

SkipE

Member
I have my first DDR machine and am still confused about this newer memory spec.
I posted yesterday about DDR, and from the replies I'm getting the picture that there are two things, not one. Please correct if I'm wrong about this.
THere is DDR and there is dual channel. Is this correct?
I inserted a 512MB PC-3200 stick into a machine that had 2-256MB sticks, and my Sandra memory bandwidth specs dropped by about 33%. I've been piecing together info, and it's getting more complicated the more I read. The one thing I know for sure is that I have to match the densities, but is there more?

I guess the best thing to do is to approach this one step at a time.
Are there two issues? DDR and dual-channel? Or are these acronyms that mean the same thing?

Thanks!
SkipE
 
DDR and dual channel are completely seperate. dual channel refers to 2 sticks of ddr running together in a dual channel compatible motherboard.
 
Thanks Nick1985.
So would it be better to run two sticks of 512 or 4-256 for best memory performance?
I need 1GB.

Thanks,
SkipE
 
2 512's. But 4 256 would be almost the same. You said that you put in ONE 512 and the memory speed dropped. That is when it would go to single channel with ONE stick.
 
It's an HP Pavilion A465C, and it says it's some kind of Asus board. It must be specially made for HP because I can't find the particular model # on the Asus site. But it must have dual channel capability, otherwise how would one explain the 33% drop in Sandra bandwidth specs when adding a 512 stick to 2-256 stick setup. A fellow replied yesterday that it was running at speed, which I take to mean it is running DDR, so it must be that it drops dual-channel if the sticks aren't matched?
 
Markfw900
No, I put one 512 into it and it had 2-256, for a total of 1GB. That's when I saw the drop in bandwidth performance...
 
You've got 2 blue slots and 2 black slots, correct?

You need 2 sticks of the same type in each set of slots.

Either 4 256MB sticks or 2 512's in the same color slots for dual channel.

It should say it's in dual channel mode at boot.

It's an ASUS P4SD board according to HP.
 
Wow, thanks LTC8K6.
Yes, I've got two blue and two black.
And yes to the P4SD. But I couldn't find detailed info on it on Asus site.

So, what happens when I have the 512 in a black slot and the 2-256 in the blue?
Does this matching only have to be according to slot color?

SkipE
 
Originally posted by: LTC8K6
I don't remember dual channel giving a 33% boost though. I thought it was more like 5%.
Click to expand...

on P4 systems dual channel does a LOT more than on AMD systems.
 
calam63
Interesting. When I use the Crucial System scanner, that's what it says my MB is.
The one I have is a microATX board, so perhaps it's the same as the p4sdx, only a micro form factor.
 
You need either one pair of modules or two pairs of modules. One solution here is to add another 512MB module like your first one. Another solution is to switch to a matched pair of 256's in place of the single 512MB module. The second pair of modules don't need to match the stock pair that HP provided, thankfully. 🙂
 
Looks like I lost LTC8K6.
Can anyone tell me: Does the matching only have to occur on the same colored slots?
If I put 2-256 in the blue slots, and 2-512's in the blacks, would my performance decrease from the 2-256 case? I have obtained the best bandwidth performance with the 2-256, and I'd like to keep it.

SkipE
 
With a motherboard like yours, you should get you can get DC with either 4x256, or with 2x512, but not with a combination like you have now, unfortunately. The 5% difference is more likely in real system performance, not in memory bandwidth only; I would guess 33% is probably about right for the change in memory bandwidth (which equates to a 50% improvement when moving TOO dual channel)

you would use 1 512 in a blue slot, and one in a black one to get dual channel
 
i can vouch for that 33%, i just got my second stick of 512 2700 back from crucial RMA and i put it in and there is an imidiate and noticable performance increase all around in every aspect of system use, i dont have any benchmarks, but its true, things ipen faster and smoother system doesnt halt when trying to do a bunch of things and such. there is a def difference between DC and non DC and also between 512 megs of ram and 1 gig
 
Thanks 3chordcharlie.
Looks like I'll be buying another 512 stick.
I'll have to find another home for these 256 sticks...
 
someone may be able to confirm this - you might be able to use one 512, and one 256 in each colour, in dc mode. I can't say for sure because I've only ever used nforce2 dual channel boards, which only have one slot for each channel - so does anyone know if this would work?
 
Originally posted by: 3chordcharlie
someone may be able to confirm this - you might be able to use one 512, and one 256 in each colour, in dc mode. I can't say for sure because I've only ever used nforce2 dual channel boards, which only have one slot for each channel - so does anyone know if this would work?
Click to expand...

no they need to be the same size
 
Originally posted by: SkipE
Can anyone tell me: Does the matching only have to occur on the same colored slots?
If I put 2-256 in the blue slots, and 2-512's in the blacks, would my performance decrease from the 2-256 case? I have obtained the best bandwidth performance with the 2-256, and I'd like to keep it.
Click to expand...
If it uses the same SIS 655 as the P4SDX, according the ASUS FAQ you can enable dual channel using 2x64 bit mode with your pair of 256 in channel 0 (one in a blue and one in a black right next to each other) and the 512 in the first slot of channel 1 (the blue one). If you ever buy another stick of 512, you can use 1.5 GB in 128 bit mode by putting one 512 stick in each of the blue slots and one 256 stick in each of the black slots. You can see their layout in the manual.

Dual channel configs are dependent upon the chipset architecture. My NF2 mobo lets me run 1GB of DDR DC with 3 sticks. The SIS 655 will let you do the same. You don't need to buy another 512 stick for dual channel (but you'll be in 2x64-bit dual channel). You will need to buy another 512 stick for maximum dual channel performance though (to get in 128-bit dual channel).
 
Originally posted by: SkipEI'll have to find another home for these 256 sticks...
Click to expand...
You have the option to leave them in there, if you like 🙂 According to HP's spec page for the Pavilion A465C it has an i865G chipset. i865G will work in dual-channel mode with a pair of 512's plus a pair of 256's, just plop a 512 in that last open slot and you're up to 1.5GB in dual-channel mode. Overkill, maybe... 😀 but it'll work.

Bigger picture: have you put in an AGP card or are you still using the onboard video? If you want to do any 3D anything, consider a video-card upgrade.
 
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