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Being the type who likes to get all the info I can so I can really understand it, I figured I would post this article here as a supplement to NoAffinity's excellent RAM 101 article. This goes into a little deeper detail as to what those timings are as well as some other things. I just thought it would be nice to have it all in one place. I did NOT right this, I just found it...so don't think I am the shizzle when it comes to memory. Enjoy...

(Copied from http://www.iamnotageek.com/a/1-p1.php...Thanks!!)

Now days it seems like everybody is tweaking their systems to get every last bit of performance out of them. Something that is often overlooked that plays a significant rold in your systems performance is memory bandwidth. This is a very tricky thing, sometimes a lower bus speed with faster timings is considerably better than just increasing your bus speed. When you are shopping for RAM you don't want to buy just cas 2 RAM. It is possible that you can get 2/3/3 RAM. You want to make sure you get good stuff. All 3 of these timings will greatly affect your system performance. You'll want to make sure you get 2/2/2 RAM what do these 3 numbers mean?

The first number is the CAS latency. The second number is the TRCD. The last number is the TRP. What on earth are these things and why do they affect my performance so much? That's exactly why I've written this article. Here we will try and explain to you what these different settings you see all the time do and try to help you have a better understanding of why these make your system go so much faster.

Cas Latency

CAS means Column Address Strobe. The Webster's Dictionary defines latency as "the interval between stimulus and response" just in case that word isn't familiar to you.

This controls the timing delay (in clock cycles) before the RAM starts a read command after receiving it. Settings are usually 2 or 2.5 This setting has more affect on system performance than any other RAM setting. Since this is the number of cycles the CAS needs to find the correct address of the data that it is looking for. That is why your entire system runs quite a bit faster when the data can be fetched in 2 cycles rather than 2.5.

I'll pull a quote from a guide from Corsair who BTW makes the XMS line of memory that I certainly approve of for high speeds and good timings.

"To understand this let's walk through a simplified version of how the memory controller actually reads the memory. First, the chip set accesses the ROW of the memory matrix by putting an address on the memory's address pins and activating the RAS signal. Then, we have to wait a few clock cycles (known as RAS-to-CAS Delay). Then, the column address is put on the address pins, and the CAS signal is activated, to access the correct COLUMN of the memory matrix. Then, we wait a few clock cycles -- THIS IS KNOWN AS CAS LATENCY! -- and then the data appears on the pins of the RAM."

RAS to CAS Delay (TRCD) This field allows you to set the number of cycles for a timing delay between the CAS and RAS strobe signals, used when DRAM is written to, read from or refreshed. Lower settings result in faster performance. 3T, 2TBank Interleave

TRP indicates how fast SDRAM can terminate one row access and starts another one.

TRAS The TRAS timing can be typically be set to 5, 6, and 7. TRAS is a timing that has little effect on performance, but has a huge effect on the maximum stable speed your RAM can run. We recommend always using the slowest (highest number) TRAS setting available; usually on AMD motherboards this would be 6 or on P4 boards this would be 7.

Row Precharge Time
This item controls the number of cycles for Row Address Strobe (RAS) to be allowed to precharge. If insufficient time is allowed for the RAS to accumulate its charge before DRAM refresh, refresh may be incomplete and DRAM may fail to retain data. 2T or 3T

RAS Pulse WidthThis setting allows you to select the number of clock cycles allotted for the RAS pulse width, according to DRAM specs. The lower this is set the faster RAM performance. 6T,5T

Bank InterleaveThis files selects 2-bank or 4-bank interleave for the installed RAM. Disabled, 2-way and 4-way.

Basically, a bank activate command can open one bank at the time and then the readout will occur after tRCD and CAS-DL. However, simultaneously, the memory controller can issue another bank activate command in the cycle after the first command was issued and, thus open the next bank. If the controller knows that the next set of data is going to be in a different bank, it can issue read commands to the next location without trashing the first bank's data burst.

Burst lengthThis is a technique that DRAM uses to predict the address of the next memory location to be accessed after the first address is accessed. 4QW, 8QW

Command RateThis is the setting that selects the speed of the SDRAM signal controller. If set to 1T, then the memory controller is running in synchronization with your bus speed. 1T will increase your memory bandwidth but a LOT of memory brands will really have trouble running this at decent speeds. This setting will have to be played with a LOT while your increasing your FSB speed. It does in fact increase your memory bandwidth but will often lower your max bus speed so much that it just isn't worth using.

ECC"ECC" stands for "Error Checking and Correction". When ECC is enabled in the BIOS the memory check will take considerably longer than it does with normal RAM. you will just have to be patient. It does not show any special messages or any info telling you why it is taking so long. ECC RAM is more expensive. On a stick of RAM that has 8 modules a ninth will need to be added for error checking. on a 16 module stick 2 more modules will be added. The added modules are what increase the price. This will hinder your performance slightly and isn't needed by us. It's geared more towards the server market.This feature is similiar to parity back in the old days. Most of the BSOD's we always saw in the win9x days get healed by having ECC memory. Commonly RAM will have an error about once a month if it is being run 24 hours a day.

(Copied from http://www.iamnotageek.com/a/1-p1.php...Thanks!!)
 

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Good stuff, bind. I edited in another "copied from" at the beginning of the excerpt, just so nobody comes here screaming plagiarism. Very useful info, tho.
 

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Good find, good job. It's exactly what I would have wanted if I were a noob too lazy to find my manual.
 

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yeah thanx for the self esteem boost zokus

but that was a great help now some one needs to explain to me memory ratios???????????? thanx
 

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I want to ask,my mb support ddr 533,what if i use ddr2 667 ,will it works? thanks for the help
 

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ok,thanks mate.
 

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Quote:

Originally Posted by zokus
Good find, good job. It's exactly what I would have wanted if I were a noob too lazy to find my manual.
i got my manual on my lap and its witten by a 4th grade dropout. "this setting adjusts the CAS latencie"
great, thanks for repeating what the BOIS says.

NOW i know what CAS latencie is, man am i tired of that chick yelling at me
"system failed doto CPU overclocking" good find man
 

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How do I go about changing my mem timings...Would that be done in my CMOS???Or through software...Please help....Uber NOOB here when it comes to overclocking...Thanks in advance
 

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Quote:

Originally Posted by Strider_2001
How do I go about changing my mem timings...Would that be done in my CMOS???Or through software...Please help....Uber NOOB here when it comes to overclocking...Thanks in advance
usually in ur advanced BIOS options
 

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well i got mine at 2-3-3-10....but P4's are different i've heard they perfer higher FSB than tighter timings...all i can say is stick around on here till someone who knows more than me can help ya
 

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If I get my timings off can I do any damage to my mem or will the performance just be bad???
 

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This is a very helpful guide. More of a neutral guide then a "intel specific" guide. May I suggest adding this to the amd memory forum. I know for me atleast, having an AMD I never thought twice to look through the intel forum sections. This guide is something I was missing, it helps for either brand. I just think more newer people, who don't have intel would notice this helpful guide if it is in the amd forums as well.
 

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Yo this may be a little off top but on an memory band test by SiSoftware Sandra 2005. It`s telling me that I have low band. test show 47% efficency.
Any Ideas on how to fix this.
 

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Ok, I've got a question here...I've found my max overclock (367 orthos stable) and now I'd like to tighten my ram timings a bit (running them 4:5). They're rated [email protected] so there should be loads of headroom (http://www.corsairmemory.com/corsair...8-8500C5D.pdf).

Now, first of all I couldn't find ""RAS activate to precharge" or "DRAM write recovery time" in the guide. Guess ASUS just uses different names for them.

So, my questions are as follows:
1. CAS latency is the most important, right? Should I lower this as much as possible until the memory tests (memtest86) starts failing and then up one notch before working on the others?
2. Will memtest fail if I go overboard, or will the computer only be more unstable?
3. Should all of these values be lowered as much as possible, or is there any that would benefit from being kept stock or even increased?

Thanks for a good thread!
 

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You know what would be really helpful.....BIOS screen shots of overclocked memory settings for different motherboards. Because each motherbord BIOS has different configurations.....This is what I want for XMAS

number of motherboards I have destroyed during overclocking experiments (while using forum instructions) = 2

Getting expensive....
 
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