DDR3 800 C6 VS DDR3 1600 C9?

[Artas1984]

I need to know what RAM settings should i use - look at my sig.

What is better? To use the default 1600 MHz rate with C9 timings or to use the lowered 800 MHz rate with C6 timings?

I have lowered my Corsair XMS3 RAM to 800 MHz in order to gain the lowest possible timings The FSB ratio is 1/2, so i don't really loose anything do i?

How would you do?

 

[homicsbane]

Definitely set it to 1600 CL9.

With my XMS3 I've managed 1333 at CL7 (quite easily). You could try your luck at that.

 

[trents]

You may find that it will not be stable at 1600 since the AMD integrated memory controller is only rated at 1333. In that case, go for tighter timings.

 

[Artas1984]

Come on people! I need more opinions! What do you use for AMD - higher FSB rate with higher timings or lower FSB with lower timings?

What do i loose if if choose the lowest 400 MHz DDR3 FSB instead of 533 MHz DDR3 FSB?

 

[EarthDog]

Tigther timings.

I woudl be shocked if an AMD couldnt handle 1600Mhz...

 

[Bobnova]

I'd be pretty surprised personally, it won't like 1600 at C7 or less most likely, but it ought to do 1600 c9. It might not, but it's worth trying.
Failing that, 1333 c8 or c7.

 

[Fr1nge]

Most IMC's on the Deneb core platform handled 1600MHz not so good. I haven't tested mine yet because I am only running @ 1333MHz. I would go for the faster frequency but tighten the timings a bit. Just experiment and see what you can achieve. Remember that OCing the NB will increase stability for your ram also. Good Luck ^_^

 

[trents]

Most IMC's on the Deneb core platform handled 1600MHz not so good. I haven't tested mine yet because I am only running @ 1333MHz. I would go for the faster frequency but tighten the timings a bit. Just experiment and see what you can achieve. Remember that OCing the NB will increase stability for your ram also. Good Luck ^_^

Did you mean to say that? It would make more sense if he were to loosen the timings when going for the higher frequency. Looser means the timing numbers are bigger.

 

[Fr1nge]

Did you mean to say that? It would make more sense if he were to loosen the timings when going for the higher frequency. Looser means the timing numbers are bigger.

Ya I meant to say that. If he can tighten them down a bit and still run them @ 1600MHz that would be awesome. There's no harm in trying.

 

[Artas1984]

So it looks like you all would go for 1333 MHz and try to lower your timings from C8 to C7..
I will remind that 1600 MHz C9 is the default, and as said by trents, AMD internal RAM controller does not work over 1333 MHz, so there is no point for 1600 MHz...

Now, why would not you, let's say, run your RAM at 800 MHz with C6?
Would you be afraid that 800 MHz rate simply would not provide enough bandwidth?
So you would rather have 1333 MHz at C8 than 800 MHz at C6?

 

[Fr1nge]

So it looks like you all would go for 1333 MHz and try to lower your timings from C8 to C7..
I will remind that 1600 MHz C9 is the default, and as said by trents, AMD internal RAM controller does not work over 1333 MHz, so there is no point for 1600 MHz...

Now, why would not you, let's say, run your RAM at 800 MHz with C6?
Would you be afraid that 800 MHz rate simply would not provide enough bandwidth?
So you would rather have 1333 MHz at C8 than 800 MHz at C6?

AMD IMC doesn't run 1600MHz to well you mean. You can run 1600MHz with a AMD processor fine, if not then all boards would be specified for ram modules only @ 1333MHz.

 

[Psykoikonov]

So it looks like you all would go for 1333 MHz and try to lower your timings from C8 to C7..
I will remind that 1600 MHz C9 is the default, and as said by trents, AMD internal RAM controller does not work over 1333 MHz, so there is no point for 1600 MHz...

Now, why would not you, let's say, run your RAM at 800 MHz with C6?
Would you be afraid that 800 MHz rate simply would not provide enough bandwidth?
So you would rather have 1333 MHz at C8 than 800 MHz at C6?

You'll probably never notice a difference from 800 C6 to 1600 C9 or anywhere in between, unless of course your testing with benchmarks. That being said 800 C6 is "slow", 800 C4 would be good. To calculate the theoretical speed take the Mhz divide by 2 (DDR) then invert the answer and multiply by the latency. The result * 1000 will be the actual time in nanoseconds (so lower is better).

Examples: 800 C6: (1/(800/2))*6=15ns
1333 C7: =~10.5ns
1333 C8: =~12ns
1600 C9: =~11.3ns

So 1333 C7 has the best theoretical latency (followed by 1600 C9) of the 4 examples. Another way to look at your title is the speed is halved (1600->800) but the latency only dropped by one third (C9->C6).

There are other variables to consider as well, the "CPUNB" speed plays a key role in how fast data moves in and out. Also Deneb is not rated for 1600Mhz Ram but there are plenty of people running it. At one time I had a 965BE C3 running 1600 C6 (Hyper ICs of course) stable, Thuban is also rated for DDR1333 and has been known to run 1600 Ram and beyond fairly easily.

 

[trents]

AMD IMC doesn't run 1600MHz to well you mean. You can run 1600MHz with a AMD processor fine, if not then all boards would be specified for ram modules only @ 1333MHz.

I disagree with that. Many, many AMD users with boards and ram rated at 1600 mhz and higher simply cannot run them at that speed in a stable fashion. We get this problem all the time on the forum.

 

[trents]

So it looks like you all would go for 1333 MHz and try to lower your timings from C8 to C7..
I will remind that 1600 MHz C9 is the default, and as said by trents, AMD internal RAM controller does not work over 1333 MHz, so there is no point for 1600 MHz...

Now, why would not you, let's say, run your RAM at 800 MHz with C6?
Would you be afraid that 800 MHz rate simply would not provide enough bandwidth?
So you would rather have 1333 MHz at C8 than 800 MHz at C6?

Actually, 1600 mhz is probably not the default speed of the ram but the manufacturer "XMP" or overclocked speed rating of the ram.

 

[Fr1nge]

Actually, 1600 mhz is probably not the default speed of the ram but the manufacturer "XMP" or overclocked speed rating of the ram.

Ya it runs 1333MHz but you have to OC it to 1600MHz +

 

[Artas1984]

Examples: 800 C6: (1/(800/2))*6=15ns
1333 C7: =~10.5ns
1333 C8: =~12ns
1600 C9: =~11.3ns

This is the explanation i was looking for. Everything is clear now.