Sign in with
Sign up | Sign in
Your question
Closed

Memory Speed vs. Timings - Experts wanted

Last response: in Memory
Share
January 21, 2011 4:40:28 PM

Sorry if this question is posted before, but I couldn't find it.

My question is quite simple, but long winded.

All things being equal (e.g. no specific brands or manufactures, thus removing fan boys), which memory speed AND timing would be recommended (e.g. not necessarily the best)?

Compare DDR3-2000 CL10 vs. DDR3-1600 CL8 vs. DDR3-1333 CL7.

Is it correct to calculate a value comparing speed divided by timing? Speed/CL?

For example: a memory speed of 2000 MT/s divided by a CAS Latency of 10 equal a number of 200. Does this value have any merit?

Furthermore: 1600/8 = 200 (same value)

And: 1333/7 = 190.43 (lower than the two value above)

Now, if know that CAS Latency (CL) is the most import factor of memory. It is the amount of time, in nanoseconds required to move information "off the chips." This would mean the lower the timing, the faster the module, within the same memory speed.

And memory speed (i.e. DDR3-2000) is rated in MT/s, not MHz. From Wikipedia: … The MT/s is normally twice that of MHz by double sampling, one on the rising clock edge, and the other, on the falling…

I just found this out, from the same link above: the higher the memory speed, the higher the peak data transfer rate, in MB/sec. I would assume that this rate can only be better achieved as you approach the lowest of CL timings.

So, using what I just found out, using the calculated values I came up with (speed/timing), given the same values, the higher speed would result in “faster” memory: DDR3-2000 CL10 would transfer data faster than DDR3-1600 CL8. Even more for a DDR3-2000 CL9 module. Much less for DDR3-1333 CL7.

I ask this because I’m contemplating a new LGA1155 build. I noticed that some motherboards only support up to DDR3-1333, others DDR3-1800, and a few up to DDR3-2133.

One of Tom’s Hardware Guide Recommended buys was Crucial’s DDR3-1333 CL9, because it could be OC’d to CL7, easily and reliably. Also recommended G. Skill Ripjaws DDR3-1600 CL9, OC’d to CL7.

But, given my figures, within a reasonable price range, wouldn’t it be better to get DDR3-2000 CL10 than the DDR3-1333, even if OC’d to CL7. And wouldn’t a DDR3-2000 CL8 module be 25% faster than DDR3-2000 CL10 (but at a 72% higher cost).

This is an example of what I found. Note how the price goes up as the CL goes down, with in the same speed:

Crucial DDR3-1333 CL9 4GB kit (2x2GB) - $49.99
G. Skill Ripjaws DDR3-1600 CL9 4GB kit - $49.99
OCZ Gold DDR3-2000 CL10 4GB kit - $54.99
G. Skill RipJaw DDR3-2000 CL9 4GB kit - $69.99
OCZ Platinum XTE DDR3-2000 CL8 4GB kit - $94.99

I’d lean towards the DD3-2000 CL9. Only $20 more than the Crucial DDR3-1333 and Ripjaws DDR3-1600, but with much higher values.

I know that It may require setting the timings in the BIOS, but I’m okay with that. As long as the board supports the higher DDR3 speeds (i.e. Asus Sabertooth P67, or P8P67-M Pro; I want Crossfire x16/x16 or x8/x8 support, too).

What do you think?

More about : memory speed timings experts wanted

January 21, 2011 5:22:25 PM

Ok, malmental....

But are timings relative to speed. If timings are rated per cycle, are the cycles the speed?

Hense, a DDR3-2000 has 1000 cycles (2000/2 due to Double Data Rate) per second, and a CL10 would "refresh" every 10 cycles.

Thus, my values work:

DDR2000 CL10 is better than DDR1333-CL7, but not DDR3-1333 CL6. Yet, DDR3-2000 has a faster transfer rate.

Score
0
January 27, 2011 6:40:04 PM

I've decided on DDR3-1600 CAS7 for my memory: G.Skill Ripjaw X Series DDR3-1600 CL7 4GB kit (2 x 2GB). It's only $5 more then the CL9 kit here for $54.99 (today?).

I got lots of info from other threads!
Score
0
Related resources
January 28, 2011 2:09:39 AM

Best answer selected by foscooter.
Score
0
a b } Memory
January 28, 2011 2:47:17 AM

I'm glad you didn't get the DDR3-2000, because you just would have wasted your money. Sandy Bridge doesn't support the 2000 speed at all -- it would have down-clocked your expensive memory to 1866 instead.

In any case, CAS Latency means a few frames per second here or there -- less than three percent difference between CL7 and CL9. It's mainly a marketing gimmick to get enthusiasts to buy more expensive memory.
Score
0
May 19, 2011 7:39:19 PM

I know this thread is old, but I haven't buit my new rig, yet.

I found this article from XbitLabs.com, and it says:

Quote:
Therefore, we believe that inexpensive DDR3-1600 SDRAM with not very aggressive timings would be the most reasonable choice for contemporary LGA1155 systems: in our opinion, memory like that offers the best price-to-performance ratio today.


Thus, I'm going with TGH Recommended Memory sticks here: 2x4GB Kingston Hyper X blu DDR3-1600 CL9. I can get them locally at MicroCenter for $99.99 here.
Score
0
May 19, 2011 7:50:29 PM

Leaps-from-Shadows said:
I'm glad you didn't get the DDR3-2000, because you just would have wasted your money. Sandy Bridge doesn't support the 2000 speed at all -- it would have down-clocked your expensive memory to 1866 instead.

In any case, CAS Latency means a few frames per second here or there -- less than three percent difference between CL7 and CL9. It's mainly a marketing gimmick to get enthusiasts to buy more expensive memory.

There is a setting in the BIOS (on my mobo at least) to turn the speed back up to what it should be.
Score
0
May 19, 2011 7:51:10 PM

This topic has been closed by Mousemonkey
Score
0
!