ddr2 2x512 vs 1024

[lancstech]

advice please on difference between ddr2 2x512 vs 1x1024?
i have 2x256 4200 ddr2 installed (dell 8400).

if i buy 2x paired 512 i fill up my 4 memory slots,
if 1 buy 1x1024 i have 1 free slot.

price for 1024 is slightly cheaper than 2x paired 512.

am i right performance isn't an issue?

 

[rvnguy]

Check, that your Dell might support 'dual channel' if so there will be info about ram must be installed in pairs and to which slots they must be paired.

Assuming this is the case there is a ram access speed advantage to this type of setup. Most mobos will allow what you want to do and the ram will be recognized but some will default to the lowest common denominator...so that if you current 2X256's are in 'dual channel' mode the addition of a single will keep this from functioning. Best to look at the dell docs for your system as the memory requirements/modes will be covered there for your specific system.

hope this helps

rvnguy
"I know everything..I just can't remember it all

 

[lancstech]

hi rvnguy,
the dell does support dual channel.
i don't believe memory has be installed in pairs.

my pdf manual states should be in installed in pairs,
else a slight perf hit but it states ensure at least a single ram in slot 1, if installing a pair in 2.

so i would have to install 1x1024 in 1, and
2x256 in slot2, if i go that route.
thanks phil

 

[cdogg]

You cannot get dual-channel with only 1 module. Without dual-channel, you stand to lose performance in some applications.

The other advantage to getting matching pairs is timing. You can rest assured knowing that both sticks have the same timing specs, which helps reduce latency.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[rvnguy]

so i would have to install 1x1024 in 1, and
2x256 in slot2

You can not install 2 modules in slot 2. If you are to add a single 1GB module leave the 2X256 where they are and add the additional module according to your manual in slot 3 or 4.

rvnguy
"I know everything..I just can't remember it all

 

[lancstech]

thanks cdogg, rvnguy
i get the dual-channel, timings, perf points,
and i was sloppy about "slots".

plan put in 1024 in dimm connector 1,
and 2X256 in dimm connectors 2 and 4 (1536 in total)
this should limit the perf hit.

later i could add a 1024 to connector 3,
and if incompatible replace the 2x256 with a single 1024()in connector 2 (giving 2048-2560).

dell recommed putting in paired ram, but manual
states "Be sure to install a single memory module in DIMM connector 1, the connector closest to the processor, before you install modules in the other connectors" which i interpret as allowing the fitting of indivual ram.

this is why i posted to see if any one else has tried it and other views which i welcome thanks. phil

 

[cdogg]

Again, paired RAM that is identical in timing specs is recommended for optimal dual-channel performance.

The part about using DIMM 1 closes to the CPU is standard on a lot of motherboards. It doesn't relate at all to how many modules you should have, just that you should start installing them at the DIMM 1 slot.

There's nothing wrong with having unmatched pairs or odd numbers, but realize that dual-channel may or may not work in that configuration, or if it does, it might be hindered by incompatibilities between the modules (causing more latency at the very least). Check the manual to see if dual-channel can work with just 3 modules and if so, which slots you have to use.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[lancstech]

hi cdogg, manual doesn't help re 1+2 config.

i know more paired ram is better,
but my gut feeling was extra single ram is still going to give me an improvement for video conversion/editing etc.

in the dim past i have discarded ram to upgrade and
i want to avoid if possible, and provide a cheaper upgrade if required.

will probably go 2x512 route, thanks for help.

 

[tf1]

Dual channel is worth about 8-12% performance improvement (size for size) over single channel. Although you are increasing the RAM by a factor of 3, you are disabling dual channel operation.

I strongly recommend getting 2x512 modules that will cost only a little more than the 1GB module but will maintain the 12% performance advantage.


Regards: tf1

 

[cdogg]

tf1,
Just a side note here...

The 8-12% figure you're talking about is in regards to the older Athlon XP systems that had it. Athlon XP's only had a 400MHz Frontside Bus, so DDR 400 in single channel worked great. Dual-channel didn't offer that much of a benefit, since the FSB was the limiting factor.

But now is an entirely different era in the PC world. The Hypertransport bus in AMD CPU's, for example, runs up to 1GHz. This extra speed allows the CPU to take full advantage of dual-channel DDR. The benefit is much greater than it used to be. The same is true for Intel P4 systems that run on an 800MHz or faster FSB. Without dual-channel memory, the CPU can really suffer in newer PC's.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[lancstech]

hi tf1, cdogg
thanks for input, i give in and will go with paired.