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n00b question on latency vs speed

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June 29, 2004 8:46:58 AM

Aloha!!

There are somethings I'd like to understand concerning memory speeds and latencies...and Fatburger's FAQs is outdated...so...here goes...

At a certain rated speed, lets say DDR400 Dual Channel, ie: PC3200...what is the difference of buying memory with different latencies....as in:

PC3200 CL3
PC3200 CL2.5
PC 3200 CL 2

Arent they ALL supposed to run at ONLY max DDR400 speeds??
And do the CL 2 modules have HIGHER potentials for overclocking? to ..say...DDR433...??

And if so....why buy DDR433 or DDR466 etc ram...Why not just buy the best DDR400 CL2 and overclock it to the max??

To summarise...I'm real mixed up....
What I know:

DDRX MULTIPLIED by TWO = DESIRED CPU FSB
so

DDR400 CL3 = 800 FSB
DDR400 CL2.5 = 800 FSB
DDR400 CL2 = 800 FSB

SO WHAT IS THE DIFFERENCE??

OVERCLOCKABILITY??
What do TIMINGS and CL 3, 2.5, & 2 have to offer in this equation?

THANKS FOR ANY HELP!!

-------------------------------
Gigabyte GA-8Ik1100/ P4C 3.0GHZ
2x256Mb Kingston Value PC3200
BBA 9800Pro 380/340
Maxtor 120GB ATA/133 2MB
Chieftec Dragon case w/ Chieftec 420W PSU
Anonymous
a b } Memory
June 29, 2004 4:40:57 PM

The CL: Cas Latency is the number of cycle the ram will take to do certain operation. It doesnt have anything to do with the memory speed(altough it is harder to get lower latency at higher clock speed).
All Pc3200 are certified to operate at DDR400speed. But memory have some Overhead. Higher quality ram will generally have more overhead...
Now a CL2 stick might have mor OC potential because it is possible to lower the latency in order to raise the clock speed. When you OC, you put more stress on your memory, when you lower the latency you remove some stress(thats the real simple explanation).Now sticks at CL3 cannot run at CL2 but CL2 stick will run at CL3...

Now you buy DDR400+ ram because its certified to run at a certain speed. There is no standard for DDRI ram over PC3200, all the PC3500/3700/4000/etc is 3200 certified to run well and stable at higher speed. If you use top notch Cl2 DDR400 you might be able to OC close to DDR500 speed but probly with much more relaxed timming than with the stick that is rated at DDR500. Also rember that OCing shorten the life of your memory.

Btw DDR400 is actually running at 200mhz , the 400 is already 200X2.
To egt to 800 you need dual channel, so its always running at 200 expect its sending 2X more info per clock cycle and when in Dual channel it has two separate lanes...800FSB is pretty much marketing stuff.

Finnaly timming aint that important on a P4 because P4's wants memory bandwith(fast FSB). AMD will benefit more from lower timmings.

Hope this helps some, other ppl might add some stuff or correct a few things =)

Asus P4P800DX, P4C 2.6ghz@3.25ghz, 2X512 OCZ PC4000 3-3-3-8, Leadtek FX5900 w/ FX5950U bios@500/1000, 2X30gig Raid0
June 29, 2004 5:58:46 PM

Ok. Traditional Ram performs one operation per clock cycle. DDR (Dual Data Rate) performs 2 operations per clock cycle (hence the name). So DDR400 is actually running at a clock of 200, but since it does 2 operations, they equate it to 400. Now, those latencies represent how many CYCLES it takes the RAM to perform a given operation. So CL = 2 means the RAM will use of 2 of its cycles to do that. CL = 2.5 means the RAM will use 2 full cycles, and one half of its next cycle (remember, DDR performs 2 operations per cycle, so for that last cycle, it uses it's first operation to finish, and then has 1 cycle free for something else). So you see, it's like kids doing SAT questions. All kids have 100 minutes, but it takes each of them a different amount of time to do 1 question. CL 2 is like the smart kid, he can do a lot of questions in 100 minutes, cl = 3 is like George Bush, it takes him longer to do each question, so he can't answer as many questions in the time alotted. Now for the rest of the bulls**t. 800 FSB is on intel only, and is actually a 200 FSB multiplied by 4. Now, since our DDR is only running at 2x the FSB, it could cause serious lag, because the processor can request information twice as fast as the memory can supply it. So, the motherboard has 2 channels. Effectively, the CPU can request information from 2 sets of ram simultaneously. Imagine a burger restaurant. They are taking 8 orders a minute, but the grill guy can only grill 4 orders a minute. To compensate, they add another grill and another grill man. Now, they can give 4 orders to one griller, and 4 orders to the other, so all 8 orders get done. Hope that answers your questions.

"It's too late now anyway. That song is stuck in my head and the only way to get rid of it is to blow it out. With a bullet!! - Carl
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Anonymous
a b } Memory
June 29, 2004 8:27:22 PM

good analogies =) specially the bush one =)

Asus P4P800DX, P4C 2.6ghz@3.25ghz, 2X512 OCZ PC4000 3-3-3-8, Leadtek FX5900 w/ FX5950U bios@500/1000, 2X30gig Raid0
June 29, 2004 9:36:40 PM

Excellent! I e-mailed that to the White House! :lol: 


"I am become death, the destroyer of worlds. Now, let's eat!
June 29, 2004 10:09:50 PM

Thx, just saw Farenheit 9/11. Either way you feel, have to admit it was a funny movie.

"It's too late now anyway. That song is stuck in my head and the only way to get rid of it is to blow it out. With a bullet!! - Carl
June 30, 2004 1:16:29 AM

Cool!!...

Thanks guys for the info.....so...IF I AM PLANNING TO OVERCLOCK MY MACHINE...which options should i go with?:

DDR400 CL2

or

DDR466-500 CLxx probably 2.5 or 3??

My rig is in my signature...there are NO reviews on the net for my mobo..so I have no idea what would be my max safest OC on the FSB...

Lets say 250MHZ is a safe bet..i guess i'll be able to achieve that...so what ram should i get??

At 250 FSB...guess my CPU will be at 3750MHZ....can that be achieved on AIR with the stock cooler....I DONOT want to change the STOCK heatsink and fan...so if that speed is TOO much for it..whats the HIGHEST speed i can reach on the STOCK heatsink and fan in YOUR EXPERIENCE??

Thanks again..

-------------------------------
Gigabyte GA-8IK1100 - P4C 3.0GHZ
2x256Mb Kingston Value PC3200
BBA 9800Pro 380/340
Maxtor 120GB ATA/133 2MB
Chieftec Dragon case-Chieftec 420W PSU
June 30, 2004 2:27:30 AM

definatly NOT 3750MHZ! Perhaps 3.2 / 3.3 Ghz

My dick is so big, that my dick has a dick. And my dicks' dick is bigger than yours.
June 30, 2004 2:36:50 AM

Are you trying to sacifice this machine to Pele'? You will never see 3.75ghz without water-cooling. Especially on a tropical island! :lol: 

"I am become death, the destroyer of worlds. Now, let's eat!
June 30, 2004 10:22:45 AM

well...ok...but WHY??

The 1.8A can OC to about 2.4GHZ...and a 2.4GHZ can OC to ~3.2GHZ on AIR....those are about 600-700MHZ OCs....

so why cant i go up to AT LEAST a ~400-500MHZ OC on air...like 3500MHZ for example??


Anyways...if the MAXIMUM i can go is like 3.2-3.4GHZ on AIR with stock HSF...Fine..but my FIRST question has not been answered ...
WHICH RAM??....look at my 2nd post please..^^

DDR400CL2....or DDR433-466-500 at CL3??


-------------------------------
Gigabyte GA-8IK1100 - P4C 3.0GHZ
2x256Mb Kingston Value PC3200
BBA 9800Pro 380/340
Maxtor 120GB ATA/133 2MB
Chieftec Dragon case-Chieftec 420W PSU
June 30, 2004 11:06:27 AM

On your question concerning latency VS speed with your system speed will be more important because P4's are very bandwidth hungry. While AMD cpu's benefit far more from low latencies.

Imagine RAM as a big warehouse, now if a worker needs to get lots of items all from the same place it would be very helpfull if he could carry lots of things at once (transfer a lot of data at one time). However if he has to go to lots of different places in the warehouse to get lots of small items it really doesnt matter how much he carrys. What does matter is how fast he can locate the item in the warehouse, this is where latency comes in. When ever a different location in RAM needs to be address there is a certain ammount of time that the RAM has to wait while address' are put on to RAS and CAS pins.
In summary, low latencies are good in some situations while high bandwidth is better in others.

The reason you cant get get much higher than 3.2-3.3 in air is that the P4 northwood is reaching the end of its life. 3.4 is probably the fastest P4 intel will release because not enough of the cores they make can go higher than 3.4 reliably. A lot of the cores prob cant do over 3.2 reliably so they downbin them to say 3Ghz perhaps (depending on demand). Now you could be lucky and get a really good core or you could get a pants one.

One thing I know for sure though is that when you start getting over 3.4Ghz your stock cooler will struggle to remove the heat generated.

When it comes to RAM you will need PC3500 at least, it is always best to keep the RAM and FSB at a 1:1 ratio (that is they are the same). PC3200 might overclock a bit but you are not gaurenteed. If I were you I would get some low latency PC3700 from OCZ.

<font color=blue>I have far too much time on my hands</font color=blue>
June 30, 2004 1:29:59 PM

thanks for your reply....as u can see from my sig...i'm currently using value kingston ram....

Would it be much trouble if you can LINK me to a SPECIFIC KIT from OCZ...one that you would suggest....

thanks again..

-------------------------------
Gigabyte GA-8IK1100 - P4C 3.0GHZ
2x256Mb Kingston Value PC3200
BBA 9800Pro 380/340
Maxtor 120GB ATA/133 2MB
Chieftec Dragon case-Chieftec 420W PSU
Anonymous
a b } Memory
June 30, 2004 1:38:57 PM

<A HREF="http://www.ocztechnology.com/products/memory/OCZ_DDR_PC..." target="_new">http://www.ocztechnology.com/products/memory/OCZ_DDR_PC...;/A>
Thats what Im using, its not really expensive and performs really nicely. If you have more money to shell out check the EB(under extreme tab).
Your shouldnt need over PC3700 with a P4C 3.0ghz...

Asus P4P800DX, P4C 2.6ghz@3.25ghz, 2X512 OCZ PC4000 3-3-3-8, Leadtek FX5900 w/ FX5950U bios@500/1000, 2X30gig Raid0
June 30, 2004 5:17:18 PM

ok, i have a question that falls under the same category. i just bought an amd 3200 clawhammer that i plan on OCing to the newcastle's core speed, 2200 instead of 2000, what type/speed/timing would you recommend? i was going to go with some corsair 3200 Xtra low latency ram because of the low timings but will that still give the the 1:1 ratio? i'm definately new at ocing so i'm not sure.
June 30, 2004 6:36:09 PM

One prob you will have is that the the multiplier on that processor is locked. In other words, it's supposed to run at 10X the fsb (10 X 200 = 2.0 GHZ). You can't set the multiplier any higher than 10. So if you want to hit 2.2 GHZ, you'll need to OC your FSB to 220. If you're ocing the FSB, you might want some RAM rated higher than 3200. Although, the Corsair might do it anyway.

"It's too late now anyway. That song is stuck in my head and the only way to get rid of it is to blow it out. With a bullet!! - Carl
Anonymous
a b } Memory
July 1, 2004 1:47:05 PM

That means you will want PC3700.
Like obtuse said you need to run your FSB at 220mhz. That means you should get ram that support up to 233mhz aka DDR466 aka Pc3700.

Asus P4P800DX, P4C 2.6ghz@3.25ghz, 2X512 OCZ PC4000 3-3-3-8, Leadtek FX5900 w/ FX5950U bios@500/1000, 2X30gig Raid0
!