Single VS Dual channel

AlabamaCajun · Jan 24, 2007

Here's a challenge.

Is Dual Channel really better then Single Channel on 64bit machines.
1 Stick or 2 Sticks (3 and 4 may taint the results but post them if you have them.

With this question, I welcome both Intel and AMD platforms but it must be a current socket 478,754 or later mobo that supports real dual channel. Please state what hardware (Example: Intel 775 C2D E6600, AMD AM2 4200X4).

What I've been hit with is that you only realize about a 1% gain with 2 sticks VS 1 stick. All the Sandras and other Benchs show more like a 40% bump. If we get anything less than 20% then dual channel is a farce!

brakezone · Jan 24, 2007

Is there such a thing a duel channel socket 754 motherboard?? I thought that no socket 754 was duel channel because the CPU only has a single channel memory controller.

As far as socket 775 or socket 939 with core 2 duo, duel channel is theoretically twice as fast.

funnyperson1 · Jan 24, 2007

Yea Socket 754 doesn't support dual channel since the in-built memory controllers didn't.

One thing to point out, you don't need to have 1x1024 and 2x512 to compare dual to single channel, just move one of the sticks to another slot.

jivetrky · Jan 24, 2007

funnyperson1 said:
One thing to point out, you don't need to have 1x1024 and 2x512 to compare dual to single channel, just move one of the sticks to another slot.

Ahh good point. That may be the best way to actually do it.

largon · Jan 24, 2007

Bandwidth makes a difference only for bandwidth intensive applications like de/encoding, de/encrypting, compressing and other calculations.

The gain is less than stellar for gaming.

AlabamaCajun said:
Is Dual Channel really better then Single Channel on 64bit machines.

64bit processing (AMD64 / EM64T) has nothing to do with memory bus width (64/128bit).

funnyperson1 · Jan 24, 2007

I think the reason he mentioned 64 bit specifically so people wouldn't bring up Athlon XP systems as evidence, because indeed single/dual didn't make a difference at all there.

MattCoz · Jan 24, 2007

AlabamaCajun said:
What I've been hit with is that you only realize about a 1% gain with 2 sticks VS 1 stick.

1% gain when doing what?

AlabamaCajun · Jan 25, 2007

MattCoz said:
1% gain when doing what?

Mostly what people on this forum run on their boxen. Folding@Home may be one of the apps that take a hit in single channel.

What is surprising is that gaming is not a big user of DC bandwidth. Granted the big bottleneck seems to be at the cpu to VC junction. A big part of time is spent by many Game Engines pushing polygons to the VC and the Game Play, Physics and AI is spent just running math calcs and executing millions of lines of code. It's just a hunch but it would explain the low data movement rates. In a way that could be a good thing that memory is not s bottleneck.

This would also mean that high end ram is moot also, would it not? (poke)

harlam357 · Jan 25, 2007

Can we have a basis for comparison Mr. Cajun man? What tests are people to run here to show results on an even keel?

What are you basing your findings on?

I seem to remember pointing out at one time that the bandwidth available to a modern(939+) AMD system is overkill... look how a C2D can smoke an Athlon in overall performance with much less ram bandwidth. I think you'll find SC a bigger hit on Intel than AMD just for that fact alone. AMD can't physically use all the bandwidth it makes available. Of course, I've always been a fan of a wider street... so I'm not complaining. I like my IMC.

emceepecks · Jan 25, 2007

Wait.... dual channel in athlon xp systems has no benefit????

Gautam · Jan 25, 2007

Hehe, I tried explaining this back in the day when I had a 754 3000+ DTR, faster than just about any Winnie out there. People thought I was nuts for recommending 754 over 939 for AGP systems (I did so because 754's mobo support was much better, and the overclockability was better)

I never tried single channel on Conroe, but honestly AFAIK its about the same story there...

But since every modern platform supports dual channel, there's no reason not to use it.

brakezone · Jan 25, 2007

socket A benifits from duel channel by a very small amount, like 300mb/s in sandra bandwidth tests.

funnyperson1 · Jan 25, 2007

emceepecks said:
Wait.... dual channel in athlon xp systems has no benefit????

It does by a couple percent in synthetic benchmarks like Sandra, but really no benefit at all in actual usage.

Gautam raises an excellent point, the performance difference wasn't that great between single channel 754 and dual channel 939.

Check out these Anandtech benchmarks comparing the two sockets:
http://www.anandtech.com/showdoc.aspx?i=2065&p=14

The biggest difference is 6% and that is in media encoding, something that is supposedly strongly dependant on bandwith.

brakezone · Jan 25, 2007

Yeah, the real world performance differences are not that great when the system already has enough bandwidth to make use of the other components.

GuitsBoy · Jan 27, 2007

So lets say someone buys two 1GB sticks, he would be better off using them as 2GB in single channel as opposed to 1GB in dual channel? Atleast in the real world?

fabulouscoops · Jan 27, 2007

GuitsBoy said:
So lets say someone buys two 1GB sticks, he would be better off using them as 2GB in single channel as opposed to 1GB in dual channel? Atleast in the real world?

Depends on the use. Dual channel will be better (faster) in benchmarks and real world apps where speed is important. But double the memory in single channel will be able to hold more in memory so loading large maps in a game might be better. If your motherboard supports dual channel, why not use it?

AlabamaCajun · Jan 27, 2007

Putting 2 sticks in single mode may bump the cmd to 2 and drag down your OC. You would be doubling the address range on that channel. I don't know about holding more in memory, it's all paged ram. There is an interleave option on some boards that I need to check out.

Linux_Box · Jan 28, 2007

brakezone said:
Yeah, the real world performance differences are not that great when the system already has enough bandwidth to make use of the other components.

That's the part most people don't understand. Many programs don't/can't take advantage so it doesn't make a difference for most people. The way some people talk about dual channel vs. single channel, you would think their web browsing would be twice as fast...

Ducatti · Jan 28, 2007

subscribed

GuitsBoy · Jan 28, 2007

But for instance on a e4300 that only has a 800 FSB anyway, and youre using pc2-6400 (800 mhz) theres no reason for dual channel anyway. Now assuming that you bumped it up to a 50% o/c, youre FSB is now 1200 mhz, with some timing tweaks i may be able to get the ram to run at 900 mhz using a 3x multiplier. Now running dual channel will at best gain you a theoretical 33% memory bandwidth, but at a 200% premium. Dosnt really seem like a bargain. I think the extra memory would do me better. I dont game, mostly just BT and firefox and photoshop chewing up all my mem.

Single VS Dual channel

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