Dual Channel question

[ln331]

I currently have 1GB (2 x 512), I'd like to get an additional 2GB (2 x 1GB), will this combination of 3GB be able to run in dual channel if the 2 pairs of DIMMs are in their respective channels?

i.e. 1.5GB in each channel:

0 - 1GB
1 - 512
2 - 1GB
3 - 512

 

[gayan]

yes they will work, but you will have to have the same density(ie size) and speed(latency) in the same channel. If you have the 2*512 in the 1st channel and the 1gig*2 in the 2nd channel it will give you the dual channel advantage.

 

[CompuTronix]

It's not ideal to mix and match memory due to latency differences and stability issues, and of course, the total memory configuration will only operate as fast as the slowest modules.

1st choice: Install two 1Gb modules, and eBay your 512's.

2nd choice: Install four 512's.

3rd choicde: Install one 1Gb and one 512 per channel.

Hope this helps, and good luck.

 

[gudodayn]

Command rate will also drop from 1T to 2T but it is of no real world significance....only in benchmark scoring where you'll see a difference in score!!

 

[ln331]

Brand/Speed/Latency are the same specs, what does density mean? Is the amount of chips on each side of the module a concern?

 

[CompuTronix]

Command rate will also drop from 1T to 2T but it is of no real world significance....only in benchmark scoring where you'll see a difference in score!!

2T command rate as compared to 1T, has a sinificant impact on 184 pin DDR memory performance. 240 pin DDR2 is 2T command rate.

Brand/Speed/Latency are the same specs, what does density mean? Is the amount of chips on each side of the module a concern?

Some 512Kb DDR2 modules are single sided while many 1Mb and most 2Mb modules are double sided, so motherboard compatibility varies with density. Using the same manufacturer, density, speed and latency spec's, module latency between 512Kb and 1Mb still differ slightly.

 

[Mondoman]

yes they will work, but you will have to have the same density(ie size) and speed(latency) in the same channel. If you have the 2*512 in the 1st channel and the 1gig*2 in the 2nd channel it will give you the dual channel advantage.

Note: only the "yes they will work" is correct; everything else stated above is wrong.

 

[Mondoman]

Command rate will also drop from 1T to 2T ...

Maybe, maybe not. It depends on the MB.

 

[Mondoman]

It's not ideal to mix and match memory due to latency differences and stability issues, ...

However, it's almost never a problem. The benefits of having more memory far outweigh any minor latency issues. Thus,
1st choice: Do as you suggested, installing 3GB w/1.5GB per channel.
2nd choice: Install two 1Gb modules, and eBay your 512's. (easier future expansion)
or
2nd choice: Install four 512's by adding two more. (cheaper)

 

[Mondoman]

... 240 pin DDR2 is 2T command rate.

No, it depends on the chipset/MB.

 

[CompuTronix]

No, it depends on the chipset/MB.

Check out the following article:

http://www.hardware.info/en-UK/news/ym6ck5qXwp6a/OCZ_releases_1T_DDR26400_modules/

Technology keeps changing.

 

[Mondoman]

No, it depends on the chipset/MB.

Check out the following article:

http://www.hardware.info/en-UK/news/ym6ck5qXwp6a/OCZ_releases_1T_DDR26400_modules/

...
:?: Not sure of your point here, except perhaps to agree with me.

The article says a specific DDR2 memory module can work with a 1T command rate.
My system (with 2x512MB and 2x1GB DDR2) runs fine at 1T.

 

[CompuTronix]

:?: Not sure of your point here, except perhaps to agree with me.

Yes Mondoman, I stand corrected.

The article says a specific DDR2 memory module can work with a 1T command rate. My system (with 2x512MB and 2x1GB DDR2) runs fine at 1T.

I wasn't aware that 1T modules were available just yet. Thanks for pointing this out. It'll be interesting to see how PC memory progresses toward DDR3.