PC2-4200,5300,6400: Whats the difference? Same in price

[tyttebøvs]

The bus between memory controller and ram transfers data twich per cycle. This goes for DDR1, DDR2 and DDR3. How fast this bus can run increases with each generation. That is it.

It is not relevant in this context how the internals of the module works, and how it achieves this goal.

 

[gamerman4]

The bus between memory controller and ram transfers data twich per cycle. This goes for DDR1, DDR2 and DDR3. How fast this bus can run increases with each generation. That is it.

It is not relevant in this context how the internals of the module works, and how it achieves this goal.

This was my initial statement

when you see DDR2-800 you divide the "800" by 4 to get the base clock speed. This helps when overclocking because it is best to run your RAM at the same base clock as your CPU FSB.

this is what was contested and it is true, DDR2-800 runs at an internal clock of 200mhz, a statement i followed by saying it helps because that it is the same as your FSB in a 1:1 ratio. I never said RAM was quad pumped but that still doesn't take away the fact that it is best to run your CPU FSB as fast as your RAM can transfer data which just happens to be 4x as fast as its internal clock (mts can roughly equate to mhz since both are a cycle-per-second measurement).

 

[StrangleHold]

The confusion might lie in the fact that the internal (chip) speed of DDR2 is half the speed of the external bus. So to get that, you divide by 4. But since it is all internal, it is rather irrlevant in these calculations.

This is the answer.

 

[gamerman4]

This is the answer.

and thats what i keep trying to say, but i wanted to argue that it is not irrelevant in the context I was using it in, internals do matter when overclocking.

 

[StrangleHold]

I think we are just butting heads on the difference between the internal and external speed of the memory in reference to the FSB and the amount of data being transferred. Good conversation though

 

[gamerman4]

I think we are just butting heads on the difference between the internal and external speed of the memory in reference to the FSB and the amount of data be transferred.

So I think we can agree that:

for DDR2 the internal speed is half of the double-pumped bus speed (obviously)
also the data transfer rate is twice the bus speed (the whole reason behind DDR2)
so in effect the transfer speed is 4x the internal memory clock and it is just a coincidence that Intel CPUs are quad-pumped so it is easy to match it with the data transfer speed of DDR2.

To elaborate on this, in the Pentium and Athlon days, DDR was standard
the internal clock = bus speed but thanks to the double-pumping, the data transfer rate was twice the internal clock

Athlon 64 cpus were 200mhz FSB and double-pumped = 400mhz
Pentium 4s (the older ones) were 100mhz FSB and quad-pumped = 400mhz
this was why DDR-400 was standard because it is best to sync CPU with the data rate, not the bus speed, BUT to get the data rate, it bases itself off of the internal clock, which is what you change in RAM when you overclock the FSB of the CPU.

This has to be the best pure technical discussion on CF we have had in a long time that hasn't involved fanboyism, flaming, or idiocy.

 

[tyttebøvs]

Sorry, but we cannot agree. You are stuck in the internal speed and that it has any relevance to this subject. It has not. DDR2 is no different in DDR in this matter. It it just able to run faster

 

[StrangleHold]

The Athlon/XP would follow that, but not the Athlon 64 (doesnt use the FSB) But thats true about comparing the data transfer vs. bus speed. But thats using the internal.

 

[gamerman4]

so the internal me clock has no bearing on bus clock at all? How is that possible when, for the bus clock to even have a purpose (or even exist) there has to be a mem clock?

The Athlon 64 may not have had a traditional FSB but its integrated memory controller did the same thing.

 

[TrainTrackHack]

I am pretty sure overclocking relies on the internal memory clock as its base.

That is incorrect. All memory clockspeeds are based on the bus speed; the internal memory clock is sort of "behind the scenes" stuff and irrelevant.

but to run your cpu in optimal sync with your RAM, you would want your CPU in sync with the transfer speed, not just the base clock which is why a Q6600 that has a 1066mhz FSB is best paired with DDR2-1066 and not DDR2-533.

THis is incorrect too. Remember the wiki article I quoted:

Example: A Core 2 Duo E6600 processor is listed as 2.4 GHz with a 1066 MHz FSB. The FSB is known to be quad-pumped, so its true frequency is 266 MHz. Therefore, the CPU multiplier is 9×. The DDR2 RAM that it is compatible with is known to be double-pumped, so to run the system synchronously (see Front side bus) the type of RAM that is appropriate is double 266 MHz, or DDR2-533.

so the internal me clock has no bearing on bus clock at all? How is that possible when, for the bus clock to even have a purpose (or even exist) there has to be a mem clock?

DDR2-800 runs at effective clockspeed of 800MTs (i.e. it performs 800 million transfers per second, or two per clock since it's DDR), external or bus speed of 400MHz (this is what should be matched with the FSB, and also what we usually consider the true memory clockspeed), and internal clockspeed of 200MHz (this is directly tied to the bus speed, and nothing's actually based on this clock, making it irrelevant in this way - it's just simply not used).

for DDR2 the internal speed is half of the double-pumped bus speed (obviously)
also the data transfer rate is twice the bus speed (the whole reason behind DDR2)
so in effect the transfer speed is 4x the internal memory clock and it is just a coincidence that Intel CPUs are quad-pumped so it is easy to match it with the data transfer speed of DDR2.

The internal speed is half of the true clockspeed, so, again, the internal clock of DDR2-800 is 200MHz, not 400MHz. When using 1:1 divider, the external (bus) speed is the same as FSB, so the internal clockspeed is half of the FSB.

 

[gamerman4]

Heh, I just realized that about 45 mins ago when I was driving down the road. I was thinking about the old P4s vs the Athlon and how their FSBs were different and stuff, lol. I guess I was thinking about it too much and when I got on the road it let me clear my head. anyways, I was thinking that the FSB was connected to the mem clock but I realised the FSB is connected to the mem bus. What I had mixed up was that I was thinking the mem clock was double pumped but I realised it was the mem bus was double pumped and it became clear. I HAVE SEEN THE LIGHT!!!!!
The main reason I was confused is that my BIOS has a multiplier of 4 but that's just the bus speed so if i had the multiplier at 4 with DDR2-800 it would actually be running at DDR2-1600 when I originally thought that it ran at DDR2-800, lol.

 

[TechShark]

I forgot to mention, I have windows Xp Pro, 32 bit, Will it be worth bumping my system up to 4gb? will it still use all 4gb? ive heard it only recognized 3gb.

 

[2048Megabytes]

I forgot to mention, I have windows Xp Pro, 32 bit, Will it be worth bumping my system up to 4gb? will it still use all 4gb? ive heard it only recognized 3gb.

If you are at 2 gigabytes (2048 megabytes) of memory that is likely plenty if you are using the Windows XP Operating System. What programs are you using with Windows XP and how much RAM do you currently have?

Edit: Windows XP 32-bit will only utilize about 3.25 to 3.5 gigabytes of RAM out of 4 gigabytes (at least that is the information I have read).

 

[TechShark]

I understand Windows xp 32bit will only utilize around 3.25gb. But other than that, lets say a program that is really high demanding( this is hypothetically speaking) and needed a lot of ram. would this "program" be able to utilize 4gb, even though xp cant utilize it all.

 

[Cromewell]

No. Programs access RAM indirectly, they go through Windows (or whatever OS you happen to be running). So anything the OS cannot use the program running on it cannot see.

 

[TechShark]

So then, I should just stick with my 3gb, Since i dunno how much .25ghz will actually make a difference

 

[Cromewell]

It's your call but 4GB probably isn't much more than 3GB and then if you ever upgrade to a 64bit OS you will have all 4GB available.