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Is Dual Channel real or BS?

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JuXsA

Registered
Joined
Sep 24, 2002
Location
Olympia, Wa
So I decided to see if this Dual channel was worth a damn. I bumped my fsb to 200mhz and dropped my memory down to 100mhz. But I run sandras memory bandwidth benchmark and all I got was 2125/1960
I have the epox 8rda+ and 256x2 xms3200

It says when I boot up the dual channel is enabled and I have the memory in the right slots.... whats the deal? If this was real dual channel shouldnt I be scoring close to 3200? I mean 100mhz doubled should be 200mhz right? Wasn't this supposed to be the big advantage of dual channel memory, Being able to lower your memory speed along with a high cpu fsb and not taking a huge performance hit?

I would post pix of the benchmark but I have no way of doing it.
 

Deathknight

Member
Joined
Sep 8, 2002
Location
Chicago
Dual channel doesn't double the speed of your memory. Its actually a pretty tiny performance increase. Memory that will run at 200mhz is pretty easy to find anyways so I would definatly run your memory sync with fsb. Its actually harder to get fsb that high than it is memory.
 

mdcomp

Classic Administrator
Joined
Nov 23, 2001
I have had the same results as DeathKnight, minimal performance increase with dual ddr over single channel at the same fsb.
 
OP
J

JuXsA

Registered
Joined
Sep 24, 2002
Location
Olympia, Wa
Ok... From what I understand when you enable dual mode, it makes twice as much bandwidth. So in single mode at 200mhz I would have 3200mb of bandwidth. I Dual mode I should theoreticly have 6400mb of bandwidth if I could get the cpu fsb up to 400mhz. This is what all the excitement over Nforce2 was about. Being able to possibly have such high bandwidth.

So at 100mhz in Dual DDR mode and my cpu with a 200mhz fsb I should theoreticly be getting close to 3200 mb of bandwidth. If 100mhz single DDR = 1600mb of bandwidth then 100mhz Dual DDR should get me around 3200mb of bandwidth.

Edit:

And when I say 200mhz fsb I mean 200x2 not 100x2
 

gtsimmo

Member
Joined
Apr 29, 2002
Location
Los Angeles, CA
Try to not get facts confused.

DDR 400 or PC3200 are rated to run at 200 mhz FSB speed, since it is DDR (Double Data Rate) that speed is effectievly doubled to 400 mhz, hence the DDR400 name.

DDR 400 is not doubled to 800mhz. Only DDR400 that runs at 800mhz are ones that run in the new Intel Canterwood Chipset that quadriples the FSB speed. 200 x 4 = 800mhz.

Double the bandwidth doesnt mean you'll double the performance. It has the extra bandwidth but it doesnt mean the memory is going to full utilize it all.

Also i dont know why you would raise your FSB to 200 mhz but lower your Memory to 100. That just doesnt make since to me. Run both your memory and FSB in a sync, the same speed. 200 mhz FSB and 200 mhz memory (remember the 200 is doubled because it's DDR, 200 x 2 = 400mhz). You should see a nice performance increase.
 

R.Rabbit

Member
Joined
Jul 19, 2002
Location
okinawa, japan
ok i understand, what you did, i did the same thing with simular results, he lowered the memory down to 100mhz so that way it should be multiplied by two because of DDR(double data rate) and then doubled again to a result of DDR-400 by the dual ddr(each ram stick gets a 64bit bus to ride on, effective 128bit bus) from this i would expect at least 2700mb/s but no sutch thing, i did more testing and found that dual ddr is only effective for a 5% increase in mem bandwith, but you can usually run at a higher fsb with only one stick resulting in better mem bandwidth, but it's good if your mem is your fsb bottleneck and not your mobo, but it's useless vice-versa
 

Captain Hilts

Member
Joined
Sep 5, 2002
Location
Toronto, ON
Yeah he's not getting the facts confused, he ran them async just to test it out (which is where dual channel should give you an advantage, if you're running them sync then you don't need dual channel anyway). I haven't done the exact same test, but I have done some tests and have had similar results. Dual channel is real in terms of the actual hardware, but I guess you can say that it's BS in terms of real world performance.

I run my two sticks in single channel, sync with the fsb, which is what I planned to do when I got this board anyway. Dual channel just gives me a very slight performance boost, but also with a little hint of instability. Not a good trade off in my mind.
 
OP
J

JuXsA

Registered
Joined
Sep 24, 2002
Location
Olympia, Wa
There we go.... you two guys understand what i have been talking about. I am back to running sycn... this was an experiment and i wanted to know why it turned out the way it did.
 

bafbrian

Member
Joined
Jan 30, 2003
Location
Atlanta, GA
Dual-Channel isn't as cracked up to be as some companies say, it will increase performance, but only a few percent, if that much.

As said before, I have had the same experiences as DeathKnight.

Only little performance increase.
 

bafbrian

Member
Joined
Jan 30, 2003
Location
Atlanta, GA
In my personal experience, it makes it easier for a person to get to a 200FSB easier though. I once took the PROC in my sig to over 200FSB, until I sold some of my better cooling parts.
 

-=TriX-R4-KidS=

Member
Joined
Mar 25, 2003
Location
Indiana University, USA
how can i even tell if dual channel is enabled?

ive got the RAM into the proper slots on my board (abit NF7-S).

i was told there is a BIOS setting I have to enable for it to work...but I dont see anything.

And what benchmarks would show a performance gain between having dual channel enabled and only running single channel?

-TriX
 

R.Rabbit

Member
Joined
Jul 19, 2002
Location
okinawa, japan
i'm not sure about NF7-S, but on my 8rda+ it says dual channel enabled at post,
use sandra to compare mem bench scores in dual channel then put the two sticks in single single channel placement and compare the results from both