Ram Memory CL5-6-6-15

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aholenstein
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Ram Memory CL5-6-6-15

Post by aholenstein » Sat Feb 02, 2008 9:58 pm

Does anyone know what those numbers mean?

What is the difference between
CL5-6-6-15
CL5-5-5-15
CL5-4-4-15
CL5-4-4-12

The Ram i have currently in my system is CL5-4-4-12 can put in ram that says CL5-6-6-15

again,
what is the difference.
Thanks,
Andreas

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martini161
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Re: Ram Memory CL5-6-6-15

Post by martini161 » Sun Feb 03, 2008 7:41 am

these are called the timings. cl stands for cas latency, and yes, these have nothing to do with compatibiliy. if you want to learn more, this site can probably explain it better than me http://www.newegg.com/ProductSort/Categ ... icleId=244

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Re: Ram Memory CL5-6-6-15

Post by Methious » Sun Feb 03, 2008 7:51 am

The difference is in timings, the lower the numbers are in the string the faster it will do the operation associated with the number. Stick with the set you have in as it's timings are lower (tighter) and will marginally operate faster. This is a simplistic answer, down in the memory forum you'll find more comprehensive information.
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Re: Ram Memory CL5-6-6-15

Post by DMB2000uk » Sun Feb 03, 2008 8:30 am

As has basically already been said, the numbers represent the amount of cycles the CPU has to wait for the RAM to be accessible after sending the request.

The lower the numbers, the better the performance of the ram. However, 667Mhz ram with CL3 timings will still not be faster than 800Mhz ram with CL4 (or even 5) timings.

Here is an explaination on how they work if you want to know more:
Memory timings

Memory performance is not entirely determined by bandwidth, but also the speeds at which it responds to a command or the times it must wait before it can start or finish the processes of reading or writing data. These are memory latencies or reaction times (timings). Memory timings control the way your memory is accessed and can be either a contributing factor to better or worse 'real-world' performance of your system.

Internally DRAM has a huge array of cells that contain data. (If you've ever used Microsoft's Excel, try and picture it that way) A pair of row and column addresses can uniquely address each cell in the DRAM. DRAM communicates with a memory controller through two main groups of signals: Control-Address signals and Data signals. These signals are sent to the RAM in order for it to read/write data, address and control. The address is of course where the data is located on the memory banks, and the control signals are various commands needed to read or write. There are delays before a control signal can be executed or finish and this is where we get memory timings. The standard format for memory timings are most often expressed as a string of four numbers, separated by dashes, from left to right or vice-versa like this 2-2-2-5 [CAS-tRP-tRCD-tRAS] . These values represent how many clock cycles long each delay is but are not expressed in the order in which they occur. Different bioses will display them differently and there maybe additional options (timings) available.



Which timings mean what?

In most motherboards, numerous settings can be found to optimize your memory. These settings are often found the Advanced Chipset section of the popular award bioses. In certain instances, the settings maybe placed in odd locations, so please consult your motherboard manual for specific information. Below are common latency options:

* Command rate - is the delay (in clock cycles) between when chip select is asserted (i.e. the RAM is selected) and commands (i.e. Activate Row) can be issued to the RAM. Typical values are 1T (one clock cycle) and 2T (two clock cycles).
* CAS (Column Address Strobe or Column Address Select) - is the number of clock cycles (or Ticks, denoted with T) between the issuance of the READ command and when the data arrives at the data bus. Memory can be visualized as a table of cell locations and the CAS delay is invoked every time the column changes, which is more often than row changing.
* tRP (RAS Precharge Delay) - is the speed or length of time that it takes DRAM to terminate one row access and start another. In simpler terms, it means switching memory banks.
* tRCD (RAS (Row Access Strobe) to CAS delay) - As it says it's the time between RAS and CAS access, ie. the delay between when a memory bank is activated to when a read/write command is sent to that bank. Picture an Excel spreadsheet with a number across the top and along the left side. They numbers down the left side represent the Rows and the numbers across the top represent the Columns. The time it would take you, for example, to move down to Row 20 and across to Column 20 is RAS to CAS.
* tRAS (Active to Precharge or Active Precharge Delay) - controls the length of the delay between the activation and precharge commands ---- basically how long after activation can the access cycle be started again. This influences row activation time which is taken into account when memory has hit the last column in a specific row, or when an entirely different memory location is requested.

These timings or delays occur in a particular order. When a Row of memory is activated to be read by the memory controller, there is a delay before the data on that Row is ready to be accessed, this is known as tRCD (RAS to CAS, or Row Address Strobe to Column Access Strobe delay). Once the contents of the row have been activated, a read command is sent, again by the memory controller, and the delay before it starts actually reading is the CAS (Column Access Strobe) latency. When reading is complete, the Row of data must be de-activated, which requires another delay, known as tRP (RAS Precharge), before another Row can be activated. The final value is tRAS, which occurs whenever the controller has to address different rows in a RAM chip. Once a row is activated, it cannot be de-activated until the delay of tRAS is over.
Taken from: http://www.ocforums.com/showthread.php?t=257741

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Re: Ram Memory CL5-6-6-15

Post by kenc51 » Sun Feb 03, 2008 10:08 am


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Re: Ram Memory CL5-6-6-15

Post by brajko2 » Sun Feb 03, 2008 2:56 pm

Yepp those where great links you've provided, kenc51, but if you look at this http://www.eclipseoc.com/index.php?id=6,51,0,0,1,0
I've found it very useful and helpful... so try with this. Also try to read some ram reviews from that site, and I'm sure that it will be much helpful to understand the whole picture.
If you specify you RAM and motherboard in more details, that would be helpful to explain what and where you have to set, to acquire best performance.

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