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Amd 7870 cpu fastest ram CPU can use? - Page 4

post #31 of 37
Quote:
Originally Posted by ubbernewb View Post

im thinking of this ram http://www.newegg.com/Product/Product.aspx?Item=N82E16820231571

Should work like a treat.

Latency is almost completely irrelevant, especially on newer APUs (Steamroller and Excavator) since the CNB has extremely high latency itself.
Personally I wouldn´t pay a penny extra for tighter latency as the bottle neck is elsewhere.
post #32 of 37
Quote:
Originally Posted by ubbernewb View Post

but wouldnt 1.7 kill it? or can it take it?

No. DDR3 can handle up to 1.9v, though you might want good case airflow if you intend to go that high. You will not get much from pushing that much voltage through your DIMMs anyway, and the IMC might not like it much either.

Regardless, I regularly use 1.7v in my Silicon Motion DDR3-2400 2x8Gb kit, and have done so since last November.
Quote:
Originally Posted by The Stilt View Post

Should work like a treat.

Latency is almost completely irrelevant, especially on newer APUs (Steamroller and Excavator) since the CNB has extremely high latency itself.
Personally I wouldn´t pay a penny extra for tighter latency as the bottle neck is elsewhere.

I disagree, at least based on Kaveri benchmarks that have shown the effects of memory latency to be quite significant. If he isn't using the iGPU for graphics, he'll rarely see any difference from higher clockspeeds at the expense of timings. Here are some simple tests I ran using SuperPi mod 1.5XS and y-cruncher at different memory and NB speeds with an A10-7700k @ 3.4 GHz (no turbo):
Quote:
DDR3-1600 7-11-11-28-1T
SuperPi
1M: 21.313s
32M: 19m 15.956s

y-cruncher
1g: 670.091s

DDR3-1600 7-11-11-28-2T
SuperPi
1M: 21.437s
32M: 19m 18.439s

y-cruncher
1g: 687.361s

DDR3-2400 10-12-13-2T
SuperPi
1M:21.312s
32M: 19m 2.346s

y-cruncher
1g: 671.984s

DDR3-1600 7-11-11-28-1T NB 2000
Super-Pi
1M: 21.266s
32M: 18m 54.628s

y-cruncher
1g: 666.284s

DDR3-2400 10-12-13-2T NB 2000
SuperPi
1M: 20.688s
32M: 18m 31.939s

y-cruncher
1g: 657.725s

Now, for my money, I'd rather have DDR3-2400 CL10 than DDR3-1600 CL7, but the two are close enough that most people would not see a difference. But, as you can see, reducing timings can make a pretty big impact on performance.

DDR3-2133 CL9 would be about the same as either solution.
post #33 of 37
Quote:
Originally Posted by drmrlordx View Post

No. DDR3 can handle up to 1.9v, though you might want good case airflow if you intend to go that high. You will not get much from pushing that much voltage through your DIMMs anyway, and the IMC might not like it much either.

Regardless, I regularly use 1.7v in my Silicon Motion DDR3-2400 2x8Gb kit, and have done so since last November.
I disagree, at least based on Kaveri benchmarks that have shown the effects of memory latency to be quite significant. If he isn't using the iGPU for graphics, he'll rarely see any difference from higher clockspeeds at the expense of timings. Here are some simple tests I ran using SuperPi mod 1.5XS and y-cruncher at different memory and NB speeds with an A10-7700k @ 3.4 GHz (no turbo):
Now, for my money, I'd rather have DDR3-2400 CL10 than DDR3-1600 CL7, but the two are close enough that most people would not see a difference. But, as you can see, reducing timings can make a pretty big impact on performance.

DDR3-2133 CL9 would be about the same as either solution.

SuperPI is a memory (DRAM & cache) bandwidth & latency test, in addition to the obvious (FPU performance).
Similar results can be achieved in LZMA compression for example, which is extremely latency & bandwidth critical.

95% of the real world applications don´t care if you are using DDR-1600 with 6-7-6-18 or 11-12-11-28 latencies.
There is no point in paying any extra for the tighter latencies, especially on AMD.

What kind of a differences you see in Cinebench, X264, X265 or in 3DMarks?

Don´t get me wrong.
If you can have otherwise fully identical modules with tighter latencies for the same price, go for them.

Never exceed 1.65V on Kaveri based parts, preferably stay below 1.625V. Carrizo / Bristol Ridge is not as sensitive since it doesn´t have the DDR3 / GDDR5 hybrid controller present in the core (DDR3/DDR4 instead). Eventhou the GDDR5 controller was permanently disabled in Kaveri / Godavari parts, the chip is still intolerable for high voltages. Older 32nm parts and 28nm Carrizo / Bristol Ridge are rated for 1.725V.
Edited by The Stilt - 10/23/15 at 2:40am
post #34 of 37
Quote:
Originally Posted by The Stilt View Post

SuperPI is a memory (DRAM & cache) bandwidth & latency test, in addition to the obvious (FPU performance).
Similar results can be achieved in LZMA compression for example, which is extremely latency & bandwidth critical.

Right, that was why I picked them. Benchmarks like SuperPi 32m will exaggerate differences in memory performance. Seeing SuperPi behave about the same on DDR3-1600 CL7 and DDR3-2400 CL10 shows that the two settings are mostly similar. Other benchmarks would be less convincing when making this point since factors other than memory bandwidth/latency determine their performance.

The whole point is that timings (and, henceforth, latency) do matter for Kaveri. They matter enough that dropping from CL10 to CL7 mostly makes up for a drop in memory clockspeed from DDR3-2400 to DDR3-1600.

The OP was interested in DDR3-2666, which is completely unnecessary unless one wants to use the iGPU (which he does not). All he needs to do is get the best combination of memory clockspeed and timings he can afford and roll with that.

I'm still skeptical about the IMC/RAM voltage limits, but I'll not argue the point. My chip ain't dead yet.
post #35 of 37
Thread Starter 
Does am3+ and fm2 Plus use the same exact socket mounting with a cooler Master 212 reason I ask is I only have the mounts for the am3+ for my Cooler Master 212 so wondering if I will need to buy another heat sink or not
post #36 of 37
The mounting pattern is identical since AM2.
post #37 of 37
Thread Starter 
ok kewl, my parts are coming by way of mailman today applaud.gif
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