View Full Version : RAM Timings?
wat is ram latency timings? i hear about all these numbers and how great this timing is n such. i've also heard tat pc-XXXX isn't all tat important if the ram timing is better.
ie. a pc-3200 ram timing blahh blah is better than a pc-4400 ram timing blah blah(worse than the 3200)
sry if this is confusing
could someone plz explain this 2 me?
03-30-05, 08:02 PM
this would really be better posted in the memory subforum
these might help you out:
http://www.lostcircuits.com/advice/bios2/6.shtml is a good introduction to waht the various timings relate to in hardware.
* 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.
This is the important thing to remember. Also here is a tip to get the most outa everything after every try run the sandra memory bandwith benchmark to see what works for you and what doesn't for you. Use the above guide when going for your timings and also remember to test for stability with memtest
The Lower the Timings, the less stability but a marginal performance increase. When you are pushing the limits of your ram, your timings wont go as low as if you are running below its recommended standard.
Oh and PS: Always run memtest86 if you start to recieve crashes, or are pushing real tight timings.
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