CL7 vs CL9

[reaper2794]

Hey guys, so Im trying to convince myself that buying CL7 RAM makes a difference between CL9

Can anyone explain to me how CL works, and how CL7 supposedly is good for gaming?

I need to learn as much as possible

 

[4745454b]

http://en.wikipedia.org/wiki/Memory_timings

Think of an excel spreadsheet. Assuming you're on the correct row already, its the number of clock tics you need to wait before the ram starts sending the info. This is why CL7 is faster then CL9 because you wait two less clock cycles before it starts sending the data. Why do you need to wait at all? I understood the term as "line capacitance" which must be wrong as there is no wiki page on it. Basically as you send the voltage down the line, the wires don't get rid of all the voltage immediately. It takes some time for the wires to reach 0 volts again. Depending on how good your ram is, the less time you spend waiting.

So how important is this? From what I've seen not much. I usually head to Anand for memory testing.

http://www.anandtech.com/show/4503/sandy-bridge-memory-scaling-choosing-the-best-ddr3/6

Not a very exciting graph is it? Remember that for gaming you need a lot of GPU and CPU "horsepower". As long as you have enough memory and its "fast enough", the timing and speed of that memory doesn't really matter. At least for gaming.

Edited for spelling.

 

[reaper2794]

So wtf is better CL even useful for /: I understand the price difference is little but Im trying to justify it

 

[4745454b]

For separating f00ls from their $$$? I only report what I know. Look over that review, decide for yourself where better ram is needed.

 

[jaquith]

It depends upon WHAT CPU as much as the CAS, and IF you plan on OC'ing the RAM and/or CPU. Most CAS 7 RAM is DDR3 1333 and there are some 'odd' DDR3 1600 7-8-7 {loose} that 'really' aren't pure CAS 7 e.g. 7-7-7. Most of the loose CAS 7-8-7 DDR3 1600 is actually under-clocked DDR3 1866+.

 

[reaper2794]

^ wtf ._.?

 

[jaquith]

You have to look at RAM as a whole Frequency {bandwidth} and CAS {pauses} with transmission. Think of is this way a car can instantly go 100 MPH but the Stops are longer (9 sec) vs 75 MPH but the stops are shorter (7 sec) both with a 100 stops in a mile. Further, the CPU however says you can run only 85 MPH.

How long does the car take to drive a mile?

That's the same as your CAS 7 vs CAS 9 question.

 

[cuecuemore]

It depends upon WHAT CPU as much as the CAS, and IF you plan on OC'ing the RAM and/or CPU. Most CAS 7 RAM is DDR3 1333 and there are some 'odd' DDR3 1600 7-8-7 {loose} that 'really' aren't pure CAS 7 e.g. 7-7-7. Most of the loose CAS 7-8-7 DDR3 1600 is actually under-clocked DDR3 1866+.

I agree with you that it depends on the CPU and what kind of OCs you want on various components, but 7-8-7 is CAS 7 the same as 7-7-7 is CAS 7, as the CAS latency is the first number! The next two numbers are the tRCD and the tRP, respectively. Granted, these numbers do contribute to an overall higher latency, but in the aggregate the CAS will affect performance most, as ultimately, the same amount (not going to happen) or more row access calls must be made than any other type, from a purely definitional standpoint.

 

[reaper2794]

What Im getting from all this is CL is basically not an important factor for gaming what so ever

Months ago ppl told me CL7 is better for gaming and thats the RAM I got..

 

[cuecuemore]

Months ago ppl told me CL7 is better for gaming and thats the RAM I got..

It depends heavily upon what game you are playing. People parrot broad, sweeping statements without the slightest idea what they mean. You have the minimalists who tell you, "DDR3 1333 CL9 is all you need for anything," which is, of course, patently ridiculous. Then you have the "sweet spot" crowd that will tell you, "DDR31600 CL7 is the 'sweet spot' for (insert popular CPU here)." This is marginally more valid than the minimalist argument, but still wildly uninformed. The truth is what jaquith said, that it depends on a variety of factors, including CPU model, frequency, FSB settings, etc. And of course, DDR3 1333 CL9 may remove all functional bottlenecks from a certain CPU/GPU setup in a given game, but not another.

 

[RetiredChief]

A Low CL rating being important is more a throwback to DDR and early DDR2.
There the frequency was lower (Longer Pulse width) so The timing was a larger factor. As 4745454b's Link pointed out there is very little diff between 1333 CL 9 and 1600 CL9. The diff between CL7 and CL 9 (at the same Freq) is nonexistant with the exception of select software and benchmarks. If Only $10 to $ 15 diff go with the best of the two, if more than $15, then go with the cheaper. (That said the link also stated 1600 CL 9 was the sweet spot for SB (set Base Freq) - Dumb me forked over for DDR3-1600 CL7, But whats $50 anyway's LOL. (More expensive when I bought.)

@ jaquith - I imagine you are referring to the Ripjaw lin. Don't really know why they changeed to Cl7,7 to Cl7,8. I bought first set (CL7,7,7,7, then seveval months latter could not find the CL7,7 so bought the CL 7,8. Low an behold Cpu-z shows the where stll Cl7,7. Any way both sets worked fin togeter. Even later bought the 2 sets 2 x 4 cl7,8 THERE is NO diff in performance between the CL7,7 and CL7,8

 

[jaquith]

^ wtf ._.?

^ wtf ._.? CPU?

This question is pointless otherwise.

Same Frequency RAM:
Example on LGA 1366 CAS 7 adds 2~4 FPS
Example on LGA 1155 CAS 7 adds 0~1 FPS
Example on AM3+ CAS 7 adds 2~4 FPS
Etc...

Multitasking - across the board CAS 7 is superior.