Sve Shto Treba Da Znate o Dual Channel Memoriji

[digitalis888]

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Introduction
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The system RAM memory prevents the PC of achieving its maximum capable performance. This happens because the processor (CPU) is faster than RAM memory and usually it has to wait for the RAM memory to deliver data. During this wait time the CPU is idle, doing nothing (that's not absolutely true, but it fits in our explanation). In a perfect computer, the RAM memory would be as fast as the CPU.

But it is very unprobable that RAM memory will one day reach CPU speed. Nowadays with processors running over 3 GHz, RAM memory is still stuck at 400 MHz (actually less than that as we will explain below).

Many years ago one idea was created to match CPU speed with memory speed, which is used until today. The processor has two speeds, one internal – which is the one labeled on the CPU, like 3 GHz, 3.2 GHz and so on – and one external, used to access the CPU's outside world, specially RAM.

But even with this technique the speeds don't match. Intel CPUs available today run externally at 400 MHz, 533 MHz, 800 MHz or even 1,066 MHz, while the RAM speed is still stuck at 400 MHz, at best (there are 533 MHz DDR2 memories emerging on the market but they are still rare).

Dual Channel Memory can help improve the RAM speed, because this technique doubles it. In order to use Dual Channel Memory, your motherboard has to be capable of supporting this technique and you will also need two equal memory modules. We'll explain this further, but first let's understand deeper the bottleneck problem.

[digitalis888]

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External Bus Speeds - AMD Processors
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As we said, the ideal scenario to get the best performance for you PC is to match the CPU external speed with the system's RAM speed. Having a RAM memory faster than the CPU external bus is not a problem, the problem is having a RAM memory slower than the CPU external bus – which happens a lot.

AMD CPUs use a technique called DDR or Double Data Rate. With this technique the CPU transfers two data per clock cycle, doubling the performance of the bus since usually just one data is tranfered per clock tick. This technique is used since the very first Athlon processor and then with Duron, Sempron and Athlon 64 processors.

Because of that, the advertised clock rate isn't the real external CPU clock. For example, Athlon XP 3200+ is said to have a 400 MHz external clock, but in fact its clock rate is 200 MHz transfering two data per clock, making it a processor with a performance similar if the CPU used an external 400 MHz clock but transfering just one data per clock.

Since it is hard do compare clocks when you don't know how much data is transferred per time, it is better to know the maximum transfer rate, given in megabytes per second. The formula to calculate it is rather simple: real clock x number of data transferred per clock x 64 / 8. 64 is used because the CPU communicates with the memory 64 bits per time, and we have to divide by eight to have the result in bytes.

Refer to the following table to know the maximum transfer rate of your AMD CPU. "External Clock" is the clock speed advertised by the manufacturer, while "Real Clock" is the real clock signal speed used by the CPU.

All Athlon 64 uses a 400 MHz external bus. To known the bus speed of your Athlon XP or Sempron processor, please read our tutorial on that subject. Duron processors up to 1.3 GHz use a 200 MHz bus, while models from 1.4 GHz on use a 266 MHz bus.



Another – and better – way of knowing your CPU external bus speed is just running CPU-Z software. Run it and check the external clock speed of your CPU on the "Bus Speed" field and check what is its maximum transfer rate on the table above.



Figure 1: Running CPU-Z on an Athlon XP system. This CPU uses a 333 MHz external bus.

As you can see on Figure 1, the CPU clock speed may not be exactly the same as shown on our table, some slight differences may occur. For example, the external bus from our CPU is running at 333.8 MHz which makes it a 333 MHz CPU.

So, once you know the maximum external transfer rate of your CPU it is just a matter of matching the memory transfer rate with it. Keep reading.

[digitalis888]

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External Bus - Intel Processors
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Intel CPUs use a technique called QDR or Quad Data Rate, which transfers four data per clock cycle. With this technique the CPU achieves an external performance four times greater than if it was transfering just one data chunk. Because of that, the clock advertised by Intel is four times greater than the real clock used by the CPU, as you can see on the table below. It is still a mystery for us if the very high-end 1,066 MHz CPU uses a 400 MHz x 4 bus or a 200 MHz x 8 bus configuration. We believe on the latter, due to the physical difficulties involved in increasing the CPU external clock rate. So, a Pentium 4 processor with 533 MHz bus runs at 133 MHz but achieves a performance "as if" it was running at 533 MHz.

Since it is hard do compare clocks when you don't know how much data is transferred per time, it is better to know the maximum transfer rate, given in megabytes per second. The formula to calculate it is rather simple: real clock x number of data transferred per clock x 64 / 8. 64 is used because the CPU communicates with the memory 64 bits per time, and we have to divide by eight to have the result in bytes.



So you need to known your CPU external clock rate to know which is its maximum transfer rate. The best way to check this is running CPU-Z software. Run it and check the external clock speed of your CPU on the "Bus Speed" field and check what is its maximum transfer rate on the table above.



Figure 2: Running CPU-Z on a Pentium 4 system. This CPU uses a 533 MHz external bus.

As you can see on Figure 2, the CPU clock speed may not be exactly the same as shown on our table, some slight differences may occur. For example, the external bus from our CPU is running at 535 MHz which makes it a 533 MHz CPU.

As we said before, once you know the maximum external transfer rate of your CPU it is just a matter of matching the memory transfer rate with it. As you can see by comparing AMD table with Intel table, Intel CPUs face more problem matching the memory speed, since Intel CPUs have a higher maximum transfer rate compared to AMD CPUs.

Let's talk now about memory speeds.

[digitalis888]

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Memory Speeds
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On the table below you see all official speeds for SDRAM, DDR-SDRAM and DDR2. DDR and DDR2 transfer two data per clock cycle, so its rated clock isn't its real clock, as it occurs with the external bus of CPUs from AMD. We listed DDR2-667 and DDR2-800 just as a reference, since these memory types are not available on the market yet.



As we've been saying, in order to achieve the top performance your PC is capable of giving you, you should match the memory speed with the CPU speed (it is ok if your memory is faster than your CPU external bus, the problem is the other way around).

Actually, if you have an AMD CPU you won't have problems. For instance, if you have an Athlon XP with 400 MHz (3,200 MB/s transfer rate) external bus just install DDR400 memories on your computer and it will work great since both the CPU and the memory will be running at the same speed grade (3,200 MB/s). You can use DDR Dual Channel to improve the performance, anyway, as we will be talking about on the next page.

Intel processors are a problem. You don't even need to have a state-of-the-art PC to have memory bottleneck. The 2.4 GHz Pentium 4 from Figure 2 would need a 4,264 MB/s memory and from the table above you can see that only DDR2-533 can provide that. If you have a newer CPU with 800 MHz external clock rate, you would need DDR2-800 memories on your PC – a memory type that was not even lauched yet!

That's why Intel is pushing DDR Dual Channel. With this technique memory bandwidth is doubled and you can match the CPU speed with memory speed.

So, specially with Intel processors, if you don't use Dual Channel Memories your PC will achieve a performance lower than it is capable of.

[digitalis888]

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DDR Dual Channel
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On DDR Dual Channel configuration, memory is acessed 128 bits at a time, instead of 64 bits, which is the normal rate. Therefore, the transfer rate is doubled. In order to use this configuration on your PC, you need to have a motherboard with this feature and two identical memory modules correctly installed (same capacity and same speed – same manufacturer and same model is highly adviced). The installation is tricky because it is not just a matter of inserting the memory modules in any of the memory sockets available.

So, with Dual Channel the memory speed doubles as you can check on the table below.



With single channel configuration we were unable to match our 2.4 GHz Pentium 4 transfer rate of 4,264 MB/s, but with DDR Dual Channel we can match this speed by installing two DDR333 memory modules! You can go ahead and install DDR400 memories if you want to.

As for Pentium 4 CPUs with 800 MHz external bus, we need a 6,400 MB/s transfer rate and two DDR400 memory modules configured as Dual Channel are capable of giving that speed grade.

As we mentioned, if you want, you can install a memory configuration higher than required.

[digitalis888]

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DDR Dual Channel Installation
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To use DDR Dual Channel configuration in order to achieve the maximum performance your CPU is capable of giving you, you will need a motherboard with this feature and two identical memory modules.

There is one exception, though: the Athlon 64 processor. On this processor family the memory controller is embbeded in the CPU, not in the chipset. Therefore with this CPU the use of DDR Dual Channel configuration depends on the CPU, not on the motherboard. Socket 754 Athlon 64 processors aren't capable of this configuration. So if you have this kind of CPU you can't use DDR Dual Channel. Socket 939 Athlon 64 processors have an embbeded Dual Channel memory controller, thus allowing this processor to use this configuration. The installation steps are the same for other kinds of processors, as we will explain below.

The instalattion, however, is tricky. You have to install each module on a different channel in order to work. The problem is that usually the modules aren't installed in a sequential order. Usually you need to install the first module on the first socket and the second module on the third socket (not the second, as you may think).

The motherboards manufacturers, in order to facilitate the memory installation, usually uses sockets with different colors for better identifying where you must install the memory modules. Usually you need to install the modules on sockets with the same color. Some manufacturers like MSI do the opposite, you must install the memory modules on sockets with different colors! And there are several motherboard models with DDR Dual Channel support that have all sockets with the same color!

So, the best way to avoid errors is to find sockets 1 and 3 and install the modules there.

We give some examples at random on the next pictures.



Figure 3: Colored sockets on a Gigabyte GA-8IPE1000 Pro 2. Just install the modules on a socket with the same color. If you install one module on a purple socket, install the other on the other purple socket.



Figure 4: Colored sockets on a Soltek SL-75FRN Golden Flame. Just install the modules on the yellow sockets.



Figure 5: Pay attention with MSI. On 865PE Neo2 you should install the modules on sockets with different colors (not same color as it happens with other motherboards).



Figure 6: Two memory modules correctly installed using DDR Dual Channel configuration (the motherboard is a Chaintech CT-9CJS Zenith).

[digitalis888]

primeticete da je tekst malo stariji ali to je nebitno ...
nadam se da tje ovo nekom pomoci

originalna lokacija teksta :

http://www.hardwaresecrets.com/article/133/1

[VojaM]

Indiskretno pitanje:
Da li si pitao ljude sa tog sajta smeš li da iskopiraš njihov materijal o postaviš ga ovde?

[glitch]

Bice od koristi nekome sigurno; ali kada bi se jos potrudio da prevedes tekst... Well, skocila bi ti rep sigurno! Pozz
PS: A da: ako ne odes u zatvor, naravno

[Shang Tsung]

VojaM kaže:

Indiskretno pitanje:
Da li si pitao ljude sa tog sajta smeš li da iskopiraš njihov materijal o postaviš ga ovde?

Ma daaaj Vojo, pa internet je freeware
Sala mala

[digitalis888]

nisam znao da je to nedozvoljeno ... obrishite shta da vam kazem ..

[ssSss]

Lepo, lepo.
Ajdj sad prevedi. Mnogi ne znaju engleski (racunajuci i mene).
Usput prepricaj, pa nece biti kopija sa drugog sajta.

[digitalis888]

lakshe ti je valjda da razumesh ovo shto ovde pishe na engleskom nego na srpskom
kad bi ti sad sve ovo preveo bilo bi ti josh konfuznije

PS: krajnje je vreme da nauchish engleski ako do sad vetj nisi ...

[glitch]

digitalis888 kaže:

lakshe ti je valjda da razumesh ovo shto ovde pishe na engleskom nego na srpskom...

Gresis. Ja sam, recimo, pobornik teze da jezik treba modifikovati shodno razvoju tehnologije: tamo gde je moguce, koristiti domace izraze, tamo gde nije - uvesti tudjice!
Ovaj tekst bi, takodje, jako lepo izgledao na maternjem...

[Shang Tsung]

Uvod

Sistemska RAM memorija sprecava PC da postigne maksimalno moguce performanse. Ovo se desava zato sto je procesor (CPU) brzi nego RAM memorija i to obicno za posledicu ima da procesor ceka dok mu RAM memorija isporuci podat-ak/ke. Tokom ovog zastoja CPU ne radi nista (ovo nije bas 100% tacno, ali se uklapa u nase objasnjenje). U savrsenom racunaru, RAM memorija bi bila brza koliko i CPU.
Medjutim, izgledi su veoma mali da ce RAM memorija jednog dana dostici brzine procesora. U danasnje vreme sa procesorima koji rade na preko 3GHz, RAM memorija je zaglavljena na 400MHz (zapravo cak i manje, kao sto ce biti objasnjeno ispod).
Mnogo godina ranije doslo se na ideju kojom ce se brzine procesora i memorije izjednaciti, a koja se koristila do danasnjih dana. Procesor ima 2 magistrale, jednu internu-koja oznacena na procesoru sa 3GHz ili 3.2GHz itd.-i jednu eksternu, koja povezuje CPU sa ostatkom sistema, a narocito RAM-om.
Ali cak i sa ovom tehnikom brzine se ne poklapaju najbolje. Intelovi Procesori dostupni u danasnje vreme rade na eksternoj magistrali od 400, 533, 800 MHz pa cak i na 1066 MHz, dok je RAM “zakucana” na 400 MHz, u najboljem slucaju 533 MHz DDR2 memorije se tek pojavljuju na trzistu, ali one su jos uvek retkost.
Memorije koje rade u Dual Channel rezimu mogu da pomognu u ubraznju RAM-a zato sto ova tehnika duplira brzinu RAM-a. Da bi mogli da koristite “dual channel” vasa ploca mora biti u mogucnosti da podrzi ovu tehniku, a takodje ce vam biti potrebna 2 istovetna memorijska modula. Objasnicemo ovo kasnije, ali pre svega cemo obajasniti ovaj problem "uskog grla".
Aj evo nesto na brzaka, uvod, nisam sad pri vremenu ...

[glitch]

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Brzine spoljne magistrale – AMD procesori
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Računar bi postizao optimalne brzine u radu kada bi učestanost rada procesora bila jednaka učestanosti na kojoj radi operativna, RAM, memorija.
Procesori firme AMD koriste tehniku poznatu kao DDR (Double Data Rate – nešto što bi se u slobodnom prevodu moglo označiti kao dvostruki prenos podataka). Sa ovom tehnikom, procesori prenose duplo više podataka (ka memoriji) po jednom takt ciklusu, duplirajući, tako, brzinu magistrale (s’obzirom da se obično prenosi samo jedan podatak po taktu). Ova tehnika se koristi od prvih verzija Atlon procesora, preko slabašnih Durona pa sve do, sada popularnih, Sempron procesora i moćnih Atlon64 CP jedinica.
Upravo iz tog razloga, postignute brzine taktova nisu stvarne brzine spoljne magistrale procesora. Na primer, za AtlonXP 3200+ se kaže da ima FSB na 400 MHz, dok u stvarnosti ona iznosi 200MHz, prenoseći duplo podataka (u zavisnosti od širine magistrale) po takt ciklusu...
Kako je teško upoređivati brzine taktova, kada nije poznato koliko podataka je prenešeno u jedinici vremena, bolje je upoređivati maksimalne brzine prenosa, izražene u MB po sekundi (koje se računaju po formuli: brzina FSB-a puta količina podataka prenešena po takt ciklusu puta 64 / 8; 64 se koristi kako procesor komunicira sa memorijom sa 64 bita a deli se sa 8 da bi se dobila brzina u bajtima).
U tabeli ispod su date maksimalne brzine prenosa AMD-ovih procesora, za odgovarajuće brzine magistrale.
Svi Atlon64 procesori koriste FSB na 400 MHz. Duron procesori, do brzine takta od 1,3 GHz koriste brzinu spoljnje magistrale od 200 MHz dok magistrala kod modela od 1,4 GHz radi na 266 MHZ. A ako koristite AtlonXP ili Sempron procesore, ko vas šiša...



Još lakši način da saznate brzinu magistrale svog procesora jeste da pokrenete CPU-Z program...



U ovom slučaju, program je pokrenut na sistemu sa AtlonXP procesorom, koji koristi FSB od 333 MHz.
Kao što može da se vidi, brzina magistrale ne mora nužno biti ista ako u tabeli (program je izračunao 333,8 MHz; ekvivalent u tabeli je pretposlednji po redu).
Dakle, kada jednom saznate maksimalnu brzinu prenosa svog procesora, bitno je složiti brzinu prenosa memorije sa njom...

digitalis, tvoj je red

[AstraLogos]

Glitch, samo da se nadovezem na podatke iz CPUZ-a. To sto se FSB od 166/333MHz ne slaze sa dobijenim rezultatom je krivnja proizvodjaca maticnih ploca koji overvoltuju namerno/nenamerno svoj proizvod pa tako zbog nesto veceg napona od default vrednosti dobije se za ~1MHz veci takt. Moja ploca Abit UL8 na defaultu radi cak na 4 MHz vecem taktu od 200MHz kolika je default vrednost. Radi se o Kingston KVR DDR 200/400.
Da nekog ne stavljam u nedoumici ovo je stari CPUZ koji ne prepoznaje bas najbolje ULI chipset pa bus speed je zatamljen a u praksi je duplo veci od HTT linka.

[AstraLogos]

Evo jednog takodje testa protoka ( opet radi se o everestu 05 koji ne vidi plocu ) i koliko je superiorniji dual chanel mod od obicnog gde nije ispred PC ispisano DUAL. Dakle overklokovana sinhrono masina na taktu od 230/460Mhz za obicnog Kingstona ovo je odlican rezultat - boldirana slova.

[Garson]

@Astra
To su samo sinteticki testovi, nazalost u realnosti dobit je plafon 10%.

[AstraLogos]

Garson kaže:

@Astra
To su samo sinteticki testovi, nazalost u realnosti dobit je plafon 10%.

Znam druze o tome smo jos 2005 na benchu raspravljali. No svaki procenat + dobro je dosao kad vec imam dual chanel up to 8GB systemskog rama.