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

[Mitch?]

yes that sounds like a good idea, just find the corsair pack that have similar timings (if the timings are too low, say the new ones you buy are lower than the ones you have, they'll just move to 5-5-5-18 anyway)

The timing doesn't make a huge difference

Timings make a significant difference. If he's using his ram to it's fullest now, tightenin the timings to 4-4-4-15 will make a difference.
I got 250 3dmark06 points, just by bringing my ram to 4-3-4-12 @ DDRII800.

 

[gamerman4]

yes that sounds like a good idea, just find the corsair pack that have similar timings (if the timings are too low, say the new ones you buy are lower than the ones you have, they'll just move to 5-5-5-18 anyway)


Timings make a significant difference. If he's using his ram to it's fullest now, tightening the timings to 4-4-4-15 will make a difference.
I got 250 3dmark06 points, just by bringing my ram to 4-3-4-12 @ DDRII800.

250 more points is by far not even slightly what I would call "significant" when points are measured up in the thousands. Also, tightening timings is more for advanced overclockers because it takes some practice and a large understanding of what the timings do and how they relate to eachother in order for them to work well. Often lower timings cause more failed POSTs than just raising the bandwidth, it is easy to get your RAM unstable with tight timings. I usually just raise timings in order to keep my RAM running at a 1:1 ratio, if it is already at 1:1 then I just keep timings at default. Lower timings mean nothing when your RAM is not at 1:1 with you CPU.

 

[Mitch?]

250 more points is by far not even slightly what I would call "significant" when points are measured up in the thousands. Also, tightening timings is more for advanced overclockers because it takes some practice and a large understanding of what the timings do and how they relate to eachother in order for them to work well. Often lower timings cause more failed POSTs than just raising the bandwidth, it is easy to get your RAM unstable with tight timings. I usually just raise timings in order to keep my RAM running at a 1:1 ratio, if it is already at 1:1 then I just keep timings at default. Lower timings mean nothing when your RAM is not at 1:1 with you CPU.

depending on his cpu, it may be at 1:1, at 3.2ghz cpu my ram runs 400mhz, and 250 does matter, considering it doesn't help the video card (as my cpu bottlenecks it), thats 250 CPU points, where it'd a fair increase.

 

[gamerman4]

depending on his cpu, it may be at 1:1, at 3.2ghz cpu my ram runs 400mhz, and 250 does matter, considering it doesn't help the video card (as my cpu bottlenecks it), thats 250 CPU points, where it'd a fair increase.

I'll agree with a "fair" increase but not significant.

 

[Mitch?]

I'll agree with a "fair" increase but not significant.

ha ok

 

[gamerman4]

ha ok

lol
I also want to add 3dmark isn't the best way to bench CPU/RAM speeds (as I'm sure you already know). I like SiSoft Sandra (freeware version is fine), it has extensive benchmarking and a lot better info than just a black and white number score.

 

[TechShark]

Thank for the info. But i meant like...heres my exisiting set up
( Slot 1) ( Slot 2 ) ( Slot 3 ) (slot 4)
Corsair Corsair (Non matching 1 g) Empty

i want to replace slot 3 and 4 with the same corsair pc2-6400 800mhz timing 5-5-5-18 memory.
and was seeing if that would be the optimal choice. for highest performance?

and another thing, If someone could explain to me.....

what "Exactly" (or closest to exactly) do the timing numbers mean? #-#-#-# ?

and why are they in the format of 3 numbers and one large one?
Thanks again, I really appreciate all this info. I still have a lot to learn..0_o

 

[gamerman4]

if you are going to have 4 of the same corsair mem, well of course that would be better, more RAM and dual channel (if your mobo supports 4 RAM sticks in dual channel). The non-matching stick would possibly causes issues in dual channel.

 

[StrangleHold]

i know what you meant but I don't believe his information sucks all the time, just most of the time so "decent" is a crappy enough word to fit without actually claiming his info completely sucks all of the time.

I'm seriously thinking of using that as a signature

 

[TrainTrackHack]

DDR2-800 has a memory clock speed of 200mhz and an I/O bus clock speed of 400mhz (what Stranglehold mentioned)

Overclocking a CPU FSB also overclocks the internal RAM clock speed.

CPU: (ill use mine as an example) Q6600
advertised FSB = 1066mhz
base FSB = 266mhz
multiplier = 9
clock speed= 2400mhz

this translates into RAM as
base FSB of CPU = memory clock speed of RAM (when using a 1:1 divider)
so
266mhz FSB = 266mhz memory clock
266FSB translates into 1066mhz FSB so you would need DDR-1066
a 200mhz FSB would need DDR2-800

so to answer your question 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.

Once you overclock it is no longer DDR2-800 but rather a higher speed.

Wrong. Firstly, FSB is quad-pumped (or quad data rate), so a 266MHz FSB effectively runs at 1066MTs. However, DDR RAM is dual-pumped (or double/dual data rate), so 266MHz DDR(2) RAM effectively runs at 533MTs. Therefore, when using 1:1 divider, 1066 FSB should be paired with DDR2-533.

And as I said, since DDR memory is double/dual data rate (or dual pumped, whichever term you wish to use), you divide the AAA in DDR(X)-AAA by 2 to get the clockspeed; you divide by four only if something's quad-pumped (/quad data rate), such as FSB.

 

[tyttebøvs]

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.

 

[StrangleHold]

Thank for the info. But i meant like...heres my exisiting set up
( Slot 1) ( Slot 2 ) ( Slot 3 ) (slot 4)
Corsair Corsair (Non matching 1 g) Empty

i want to replace slot 3 and 4 with the same corsair pc2-6400 800mhz timing 5-5-5-18 memory.
and was seeing if that would be the optimal choice. for highest performance?

and another thing, If someone could explain to me.....

what "Exactly" (or closest to exactly) do the timing numbers mean? #-#-#-# ?

and why are they in the format of 3 numbers and one large one?
Thanks again, I really appreciate all this info. I still have a lot to learn..0_o

Yes, getting the same 555-18 would be your best bet, having them all the same. But the 555-15 would not hurt anything, if its the same voltage the timing is just off by a small margin and would backclock to 18 anyway if set to auto. As far as what they mean. A short version.

CAS - You could look at it like the delay time in a cycle.
tRCD - The time in a cycle to active a command.
tRP - How long it takes to swap memory banks.
tRAS - the amount of time between being precharged and deactivated

 

[gamerman4]

Wrong. Firstly, FSB is quad-pumped (or quad data rate), so a 266MHz FSB effectively runs at 1066MTs. However, DDR RAM is dual-pumped (or double/dual data rate), so 266MHz DDR(2) RAM effectively runs at 533MTs. Therefore, when using 1:1 divider, 1066 FSB should be paired with DDR2-533.

And as I said, since DDR memory is double/dual data rate (or dual pumped, whichever term you wish to use), you divide the AAA in DDR(X)-AAA by 2 to get the clockspeed; you divide by four only if something's quad-pumped (/quad data rate), such as FSB.

ummm.....http://en.wikipedia.org/wiki/DDR2_SDRAM
read the chart but here is a quote

Like all SDRAM implementations, DDR2 stores memory in memory cells that are activated with the use of a clock signal to synchronize their operation with an external data bus. Like DDR before it, DDR2 cells transfer data both on the rising and falling edge of the clock (a technique called "double pumping"). The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four bits of data can be transferred per memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR.

so DDR2 is double pumped and twice the clock speed at the bus but the internal speed equals the CPU FSB (on a 1:1 ratio).

if FSB = 266mhz then DDR2 RAM = 266mhz internal
Core2s are quad-pumped while DDR2 is double pumped while running at double the rate of DDR so

266FSB quadpumped = 1066FSB
and
266mhz mem clock double pumped with double clock = 1066mhz.

 

[TrainTrackHack]

so DDR2 is double pumped and twice the clock speed at the bus but the internal speed equals the CPU FSB.

FSB = 266mhz then DDR2 RAM = 266mhz internal
Core2s are quad-pumped while DDR2 is double pumped while running at double the rate of DDR so

266FSB quadpumped = 1066FSB

266mhz mem clock double pumped with double clock = 1066mhz.

Like tyttebovs said, the internal clockspeed doesn't matter (since it's half of the external speed and that can't be changed). The memory bus clockspeed is still the same as FSB clockspeed when the divider is set to 1:1. DDRn RAM is rated at double the external clockspeed, or the bus speed; hence, the rating of Dual Data Rate RAM should be half of the rating of the Quad Data rate FSB. Since I'm a nice boy P), I bolded the incorrect part for you; as I said, the external memory clock is the one that runs in sync with the FSB when the divider is set to 1:1. The internal clock speed, in your example, would be the half of the external clock, or 133MHz, whereas you seem to think that when the divider is 1:1 the FSB the internal clockspeed of the RAM will be synced with the FSB - this is incorect.

From wikipedia: http://en.wikipedia.org/wiki/Pumping_(computer_systems)

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.

 

[TechShark]

Not sure if i'm getting this completely right but, when it comes to the numbers "#-#-#-#" or my "5-5-5-18" the smaller the number the better?

being that the transfer rate is faster? err i think right?

 

[TrainTrackHack]

Not sure if i'm getting this completely right but, when it comes to the numbers "#-#-#-#" or my "5-5-5-18" the smaller the number the better?

being that the transfer rate is faster? err i think right?

Yes, lower timings are better; lower timings simply decrease the latency i.e. the time it takes before the CPU will actually get the data it requested, but doesn't really affect the speed (the throughput remains the same regardless of timings).

 

[tyttebøvs]

(the throughput remains the same regardless of timings).

About throughput. I would think that the delay in time between commands and how long a command takes to execute will affect the overall throughput.

 

[TrainTrackHack]

About throughput. I would think that the delay in time between commands and how long a command takes to execute will affect the overall throughput.

In theory, throughput will remain same regardless of timings, since timings simply specify how many clock cycles it takes to retrieve data - even if the timings are set higher, the memory can still handle the same number of transfers as before providing that the clockspeed doesn't change. However, in practice performance will suffer since the CPU has to wait longer for the data, and while waiting it will pretty much sit idle meaning that there are no memory I/O operations, hence the available bandwidth will not be utilized.

 

[tyttebøvs]

In theory, there will also be no data on the bus while the ram prepares for data to be transfered. Increase the delay and less data will be transfered over time.

 

[TrainTrackHack]

In theory, there will also be no data on the bus while the ram prepares for data to be transfered. Increase the delay and less data will be transfered over time.

I'm not sure what you mean here... if DDR memory runs at 800MTs, it can (in theory) perform 800 million transfers per second, regardless of timings; the RAM can accept commands at a rate specified by effective clockspeed while other data is being prepared for transfer.