DDR vs DDR2 vs Dual Channel

[Ethereal_Dragon]

I am looking to build a new system... I most of the components picked out, with the exception being the RAM...

It's going to be an Athlon 64 system, using this Motherboard: ASUS A8N-SLI

http://www.newegg.com/app/viewProductDesc.asp?description=13-131-517&depa=0


The page shows:

"RAM: 4x DIMM DualChannel DDR 333/400 Max 4GB"

Is DualChannel DDR and DDR2 the same thing, or are they completly different? Newegg shows that DDR RAM is 184 PIN, and DDR2 is 240 PIN... Does anyone know which this board accepts?

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[Rugger]

You can download the manual from the mfr website to get the specifics on what the board supports.

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[Ethereal_Dragon]

thanks... I had checked the ASUS website, but didn't think to download the manual....


For reference for others..... This board uses 184 pin DDR RAM.

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[endyen]

Just as a general heads up, no Amd system uses DDR2 at this point. DDR2 will continue to slow your system down, because of high latency, till it has a 333/666 memory bus. Even then, if the memory, and fs buses are out of sync, gains would be minimal.
Amd has said they will not use DDR2, until it offers gains, and the cost is in line.
Intel on the other hand is cramming DDR2 down peoples throats. The "new centrino" systems will all have to use DDR2 @ 133/533 speeds. This will have a very negative effect on memory intensive progs. Should help to sell the new Turion chips from Amd.

 

[jammydodger]

All new athlon CPU's use 184pin DDR RAM, AMD are not going to support DDR2 till 2006. At the moment DDR2 is just for Intel systems.

Dual channel mode can be used on both DDR and DDR2 systems, it basically cobines 2x64bit RAM channels into a single 128bit channel, thus providing twice the effective bandwidth. It requires 2 or 4 equally sized RAM modules (prefferably specailly matched pairs).
Athlon XP systems use a slightly different version of dual channel mode but u dont have to worry about that.

 

[pat]

"Athlon XP systems use a slightly different version of dual channel mode ..."

which is?

-Always put the blame on you first, then on the hardware !!!

 

[jammydodger]

The XP systems stagger the latencies rather than combine the channels. This is because there would be little point in offerring 6.4GB/sec of bandwidth (PC3200 dual channel) when the CPU to northbridge bus can only support 3.2GB/sec of bandwidth.

 

[pat]

There is still little point offering 6.4 GB/sec on current 939 CPU because the bus speed is still only 3.2 GB/sec. The wider bandwidth just make sure that the bus is alway saturated with data and that what give the dual channel the 5-7% speed avantage over single channel. The performance gainfor AMD 64 CPU is much more because of the higly efficent on die memory controller than it's memory bandwidth.

It is much more a marketing trick than a useful feature on AMD. Intel has it so I guess AMD should have it.

Maybe I'm wrong too.

-Always put the blame on you first, then on the hardware !!!

 

[Unolocogringo]

Dosen't the 915 series chipsets support DDR AND DDR2???

I aint signing nothing!!!

 

[jammydodger]

Ummmmm I think you are a little confused, socket 939 CPU's have an onboard memory controller which means they communicate directly with the RAM. There for the bus speed between the CPU and RAM is exactly what the RAM can provide (in the case of PC3200 in dual channel that is 6.4GB/sec). The Athlon64/FX does not have a fixed speed memory bus.

 

[tweebel]

Chipset might support it, you can't have both on the same MB and thats what its about.

 

[pat]

I know about the on die memory controller stuff, but how come the CPU performance doesnt improve more that some % for same die/cache/GHz cpu while the memory bandwidth double?

I guess that the CPU cannot process more instruction that it is now and PC3200 memory is just about what it needs. If it has a long pipeline, like the P4, needing more data to keep it full, then I guess that higher bandwidth would have done a difference. Maybe better/optimized core will make better use of the extra bandwidth


-Always put the blame on you first, then on the hardware !!!

 

[Crashman]

I think the Mobile 915 supports both DDR and DDR2 just as the desktop version does.

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[Crashman]

You can't have both types of RAM installed at the same time, but you can have both types of slots on the same board.

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[endyen]

It seems the new sonoma cores will use the Alviso chipset. It does not support DDR, only DDR@ according to <A HREF="http://www.theregister.com/2005/01/19/intel_launches_sonoma/" target="_new">http://www.theregister.com/2005/01/19/intel_launches_sonoma/</A>, or am I confused? Sure seems like Intel is up to it's old bullying ways to me. Ram it down the consumer's throat. Who cares if it's no good, or if they dont like it. Just dont let them choose.

 

[dbruynmf]

Fair enough, same as with rambus. But keep in mind that DDR2 will be better once it reaches 667MHz and Technology always has a tendancy to start a new standard/product slower than the previous version's fastest model.

 

[jammydodger]

Yeh I think it is just the arcitecture of all athlon CPU's, they do not seem to benefit from memory bandwidths over 3.2GB/sec...they just dont need it (I think it is to do with the shorter pipeline as you said).