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Old 11-21-2007, 05:15 PM   #1
RockyIV
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Default Dual Channel Benchmark showing no improvement

Hi, I have red article http://www.hardwaresecrets.com/article/133 which is very good and I tough I understand it, but...

I have run sisoft Sandra benchmark for RAM bandwidth in single and dual channel configuration and improvement was 17%, shouldn't it be double?
CPU: Celeron 2.8 GHz
MBO: Asus P4S800D-X
RAM: 2 x 215MB DDR PC2700

CPU-Z tool results:
Bus Speed: 133.4 MHz
Rated FSB: 533.5 MHz

Single channel results are about 2200 MB/s
Dual channel results: 2900 MB/s
(Results are average after few runs)
Benchmark tool also noted 51% for single and 68% Bandwidth efficiency for dual channel.
What should I do to improve that?

To make things worst, I just bought 2x1 GB Samsung DDR 400 MHz PC3200 and installed them correctly in blue slots as it is instructed in manual, but bandwidth is again about 2700 MB/s.
Shouldn't it be 2x3200= 6400 ?
BIOS settings for DDR are on Auto and results are same if I set it to 400 MHz.

Thanks for your help
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Old 11-22-2007, 03:57 AM   #2
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LoL its funny you mention this...

Last edited by ElXtronic; 11-22-2007 at 04:10 AM.
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Old 11-22-2007, 04:09 AM   #3
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I Had posted an explaination about how Dual Channel works awhile back, though Gabriel told me i was wrong for thinking the improovement from Dual Channel was not double(though technically shows its possible), I made it quite clear it wouldnt reach that stage.

My theory behind Dual Channel is because its accessed in parellel, the system has to wait about 25%-30% longer for the 3rd Bank(2nd DC bank except in MSI Boards where its 2nd bank) to register after the first bank due to its physical length. If you notice on your board if it has DC and its not an MSI(which i believe they are the only company who realizes this effect), the length between each bank is somewhat seperated from the location of ur CPU, the original RAM in single channel allocates 64-data bits per clock, and if you add another in DC with it its a combined 128-date bits per clock. This doesnt mean what so ever that the amount of data will be processed 2x as fast just because it is technically sending more data per clock, time is allways a factor and your CPU must wait for both banks before resending. Its a Read/Write process, to think otherwise is foolish. Data bundles in quantity so a pure 100% improovement is not practical, but if you benchmarked an MSI board, im sure you would most likely see a 8%~ improovement out of running in DC.

I hope this also answers many folk's question on why MSI sets up their DC in the mannor they do, im sure the more experianced techs where wondering why this is.

Thank you for posting your experiance, maybe Gabriel will take my theory of interleaved queeing in DC seriously now lol doubt it though
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Old 11-22-2007, 10:48 AM   #4
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Hi there,

The bandwidth gain will depend on the memory controller. As Intel CPUs don't have an embedded memory controller, the gain is limited by the chipset you are using. The numbers you present are correct.

You will see a far higher improvement on AMD CPUs, where the memory controller is inside the CPU and far more efficient.

At the end of the day, the overall performance gain is also questionable, as at least 80% the CPU does not access the RAM memory directly but the memory cache, and that is why usually benchmarking programs do not show any significant improvement by using dual channel vs. single channel.

Cheers,
Gabriel.
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Old 11-22-2007, 11:27 AM   #5
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Quote:
Originally Posted by Gabriel Torres View Post
Hi there,

The bandwidth gain will depend on the memory controller. As Intel CPUs don't have an embedded memory controller, the gain is limited by the chipset you are using. The numbers you present are correct.

You will see a far higher improvement on AMD CPUs, where the memory controller is inside the CPU and far more efficient.

At the end of the day, the overall performance gain is also questionable, as at least 80% the CPU does not access the RAM memory directly but the memory cache, and that is why usually benchmarking programs do not show any significant improvement by using dual channel vs. single channel.

Cheers,
Gabriel.
AMD = shorter travel distance. Though i am glad that Gabriel does see where im coming from he did point out a good point that i hadn't mentioned and that is that the CPU has a majority of quick access allocating to its Cache Levels. He is correct, the programs you use for benchmarking would go off how everything is handled and if the RAM was the only factor then the difference would be shown in a clearer state. Hes a smart guy what can I say.

But ya i sure can't wait for the MCC integrated Intel CPUs which are coming out here shortly(or so is said 'Soon' since 05) lol. Anybody have a released date on this?
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Old 11-22-2007, 12:56 PM   #6
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whats MCC an abreviation for?

I know that they are bringing the intergrated memory controller into the new 'nehalem' core.
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Old 11-23-2007, 08:47 AM   #7
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Thanks for explanation, sorry if I ask stupid question..
But why Asus made mother board which support DDR ram frequency 533 MHz, and fastest DDR is at 400 Mhz?
And why did they made mother board for Pentium with dual channel if there is no use of dual channel for Pentium?

I don't expect double performance, but at least something... Same benchmark test provides reference point of other configuration and my is way bellow it should be.
Please take a look at the picture, I would appreciate if someone could answer how to achieve optimum speed:

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Old 11-23-2007, 09:07 AM   #8
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to get the max performance, you can do three thing's

1) increase the clock speed
2) tighten up latency timings
2) sync the RAM with the FSB

the two important ones are the clock speed and syncing it with the FSB but obviously you need a balence with the latencies as well.

if you have decent RAM you might be able to get the speeds up too 533mhz or 532 (266Mhz *2) in your case, and thus match it 1:1 with the FSB

but you will have to have a play with it and see what happens
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Old 11-24-2007, 06:02 AM   #9
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Quote:
Originally Posted by reidy- View Post
whats MCC an abreviation for?

I know that they are bringing the intergrated memory controller into the new 'nehalem' core.
Memory Controller Chip, thanks for saving me research time Reidy.
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Old 11-27-2007, 02:46 PM   #10
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Quote:
But why Asus made mother board which support DDR ram frequency 533 MHz, and fastest DDR is at 400 Mhz?
For overclocking.

When you increase your external clock rate you automatically increase the memory clock.

For example, on your computer you have a CPU running externally at 133 MHz and memories at 166 MHz (DDR333 = 166 MHz x 2). This means that the FSB/memory ratio is of 1.25x.

So if you overclock your CPU from 133 MHz to 150 MHz, for example, your memories' clock will automatically increase to 187.5 MHz or 375 MHz DDR. Thus your memories will be working at a clock higher than their labeled clock.

Of course several motherboards have a configuration for the FSB/memory multiplier/divider so you can change the FSB/memory ratio to make the memories to run at a lower speed, closer to its specs.

But the idea is that when you overclock your CPU you reach an overclocking limit, and you never know what is exactly limiting you from overclocking even more. Sometimes it is the memory that is limiting your overclocking, because they are running at a clock higher than they are capable of. Using a overclocking-oriented memory on your system you can be sure that if the memory maximum clock rate wasn't reached, then it is something else that is holding your system from a higher overclocking. For example installing a DDR-533 memory on your system you can be sure that your memories will work at least up to 533 MHz (266 MHz x 2).

Notice that when you install this kind of memory on a regular system without overclocking they will work at a lower clock rate (e.g. DDR-400).

In this ASUS case probably the motherboard has a multiplier to make the memories to work at 533 MHz even when you are not overclocking your CPU. I am just guessing since I am not familiar with this particular model.

I hope I was clear enough for everybody to understand this important subject.

Cheers,
Gabriel.
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