Understanding RAM Timings

**Hardware Secrets Team** · 06-13-2006, 05:13 AM

There has been a new article posted.

Title: Understanding RAM Timings
URL: http://www.hardwaresecrets.com/article/26

Here is a snippet:
"DDR and DDR2 memories are classified according to the maximum speed at which they can work. But, besides the speed, there is another information that tells you the memory performance: timings. Timings..."

Comments on this article are welcome.

Best regards,
Hardware Secrets Team
http://www.hardwaresecrets.com

robmad · 06-13-2006, 11:20 AM

"Thus the period of each clock cycle of a DDR2-533 memory running at 533 MHz (266.66 MHz clock) would be 3.75 ms. Keep in mind that you need to use the real clock rate, which is half the labeled clock rate. So this DDR2-533 memory would delay 18.75 ms to start delivering data, if it had CL =5, or 11.25 ms, if it had CL =3, for example."

Have you forget the prefix "Million Hz" i think you shall calculate again. I am confused. If its true that you telling me shall the RAM access time be like a new HDD.?!

**Gabriel Torres** · 06-13-2006, 05:17 PM

Ops, typo! Fixed. The correct unit is ns (nanosecond).

Cheers,
Gabriel.

Aleksaas · 09-24-2008, 08:38 AM

Great tutorial,well done!
I have just one question.When I want to calculate waths the best for my system performance I know I need to use formula T=1/f to get cycle time in nanoseconds,but do I need to multiple it just with CL to get delay or I need to add all timings(CL,tRCD,tRP,tRAS),for example 2.5+3+3+7=15.5 and then multiple 15.5 with cycle time?Or something else?

**Gabriel Torres** · 09-30-2008, 04:09 PM

Just CL.

CL, CAS Latency, is what was used to be called "access time". It measures the time the memory delays between receiveing the command from the memory controller and return the requested data.

See the figure below for a better understanding.

Cheers,
Gabriel

06-13-2006, 05:13 AM	#1
Hardware Secrets Team Administrator Join Date: Nov 2004 Posts: 2,952	Understanding RAM Timings There has been a new article posted. Title: Understanding RAM Timings URL: http://www.hardwaresecrets.com/article/26 Here is a snippet: "DDR and DDR2 memories are classified according to the maximum speed at which they can work. But, besides the speed, there is another information that tells you the memory performance: timings. Timings..." Comments on this article are welcome. Best regards, Hardware Secrets Team http://www.hardwaresecrets.com Last edited by Gabriel Torres; 06-13-2006 at 05:18 PM.

09-30-2008, 04:09 PM	#5
Gabriel Torres Administrator Join Date: Oct 2004 USA Posts: 2,553	Just CL. CL, CAS Latency, is what was used to be called "access time". It measures the time the memory delays between receiveing the command from the memory controller and return the requested data. See the figure below for a better understanding. Cheers, Gabriel Attached Thumbnails

Laptop Deals			Powered by Shopping.com
Acer (LU.S680B.066) PC Notebook From $256	Acer AOD250-1116 (LU.S700B.029) Netbook From $287	Toshiba NB205-N310/BN (PLL20U-00201D) Netbook From $367	Acer Aspire One AOD250-1326 10.1-Inch UltraThin Seashell White Netbook - 3 Cell Battery (LU.S690B.037) From $287	ASUS Eee PC 1005HA-PU1X-BK Netbook From $355

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

06-13-2006, 11:20 AM	#2
robmad Junior Member Join Date: Jun 2006 Posts: 2	"Thus the period of each clock cycle of a DDR2-533 memory running at 533 MHz (266.66 MHz clock) would be 3.75 ms. Keep in mind that you need to use the real clock rate, which is half the labeled clock rate. So this DDR2-533 memory would delay 18.75 ms to start delivering data, if it had CL =5, or 11.25 ms, if it had CL =3, for example." Have you forget the prefix "Million Hz" i think you shall calculate again. I am confused. If its true that you telling me shall the RAM access time be like a new HDD.?!

06-13-2006, 05:17 PM	#3
Gabriel Torres Administrator Join Date: Oct 2004 USA Posts: 2,553	Ops, typo! Fixed. The correct unit is ns (nanosecond). Cheers, Gabriel.

09-24-2008, 08:38 AM	#4
Aleksaas Junior Member Join Date: Sep 2008 Posts: 1	Great tutorial,well done! I have just one question.When I want to calculate waths the best for my system performance I know I need to use formula T=1/f to get cycle time in nanoseconds,but do I need to multiple it just with CL to get delay or I need to add all timings(CL,tRCD,tRP,tRAS),for example 2.5+3+3+7=15.5 and then multiple 15.5 with cycle time?Or something else?