DDR Basic

Hello Guy's
i want to purchase the new ddr for my system but i don't familiar with this technology specially the Ram differentiated on the basis of CAS 2 or 2.5 or 3 what are these things also i don't know are what latencies in Ram.
Any Help will be appreciated. also a defined the spec of it ram in the following manner can some one tell me what it is.
2.5 2 2 6

Hi, in regards to your questions:

DDR is Double Data Rate RAM, it is SDRAM however DDR RAM can be accessed on the ups and downs of a clock cycles (Like a rolla coaster) however with SDRAM only access on the downs.

CAS is refereced to as CAS Latency, this is the amount of cycles it takes between activating the CAS signal/address and the placing of the single bit/data onto the register in which can be then taken up the databus to the CPU to process.

Try to think like this: The lower the CAS the better

CL2.5 2 2 6

Is equal to:

Overal latency is 2.5
CAS Latency is 2
RAS-CAS Delay 2
RAS precharge 6

CAS Latency is the time delay between the inputting of the COLOMN address into address pins/activation of CAS signals and the reading of data from the pins. The higher the value the longer the wait to read the data, if CL3 then 3 cycles need to pass before you can read the data. This is where the cell is discharged (where the data is read) and then recharged to its original state.

RAS Precharge is used to charge the cells before the accessing (read/write) of the cell occurs; this is because when the memory is being accessed it cannot be charged simultaneously and the cell may lose its charge (due to leaking) so before the accessing takes place the memory is precharged.



RAS-CAS Delay is the amount of clock cycles, which take place between the activation of the row address using the RAS signal and the sending of the column address to the address pins. RAS-CAS Delay involves different tasks including CAS Precharge.

Again think about it as: The lower the value, the faster/better - higher performance.

Regards

DislexiK

Hey everyone, I'm looking at some Corsair Value RAM, but I'm trying to cut costs. Would 512 be enough to run HL2, Far Cry and UT2k4? I'd most likely buy another 512 in a year or so... Thanks for any input!

OK HERE IS A VERY NICE AND INFORMATIVE LINK FOR EVERYONE WHO IS WONDERING ABOUT THE FOLLOWING:

1. WHAT IS DDR
2. WHAT IS LATENCY
3. HOW DOES RAM WORK
4. WHAT SHOULD I LOOK FOR WHEN BUYING DDR


CORSAIR MEMORY BASICS

It is a sticky now, so anyone who feels like asking these questions over and over, please refer to this wonderful presentation accompanied by a lady's voice.

DevHardware's Memory Basics

No woman's voiceover, and it's starting to get a bit dated... but hell, I wrote this. It's not ready to go into retirement yet.

Wow that was informative!!! Everyone should listen to that b/c it explains everything you should need to know!

Yes, that was a very well put together presentation. DMOS, yours is great too, but the Corsair one is nice for those who need pictures and voices. Good for newbies!

Are you calling me a newbie

Im a noob!

not at the same time

I have a quation about ram. I'm looking at this set to buy: http://komusa.com/1gbkit5pc46d3.html

my chipset is supported(865PE) and my mobo(A-Bit IS7) supports dual channel. My question is, my motherboard says it supports Dual-channel DDR400, but this is DDR466. I figure that my motherboard says DDR400 becuase its an 800Mhz FSB board. Also i figured that 466Mhz would be best since my processor runs at 235Mhz which would translate to 470Mhz the way the memory speed is defined. SO my question is would my system support it, would it run at 466Mhz or be downclocked to 400Mhz, or will it not support it at all.

if possible, have the memory run in sync with your cpu, so you would have the mrmory run at 470, which is slightly over spec but not much. if your motherboard won't automatically let you run your memory in sync, and you can't raise the mem frequency beyond 200 (400), then you'll be stuck at ddr400

yeah, i was thinking if I can't increase my memory to 470 I could always lower my CPU to 466, its only 2Mhz on the FSB so it really would make a difference. My concern is still if my Motherboard will run it at 466 becuase if not then I might as well save myself the $36 difference. I'm going to look in my BIOS to see if I can have any control over Memory Frequency, I'm new to memory so I have no idea how I would go about changing something like that, I don't remember seeing an option before. The only things I know how to change are timmings(although I don't nkow what they do but no point learning right now) and the ratio

Drumz, if you can spend another 30 bucks this memory will run at you 235 easy. It can do near 270ish if pushed. And will keep better timings.