DDR3, does it 'do' 5-5-5-15/18 ?

[Terbinator]

The RAM I'm using is in the spec to the left and for the life of me I cant get to run @ 5-5-5-15/18.

It simply refuses to boot even @ 1066MHz (I've not tried 800) with 1.65v, obviously I don't want to be going any higher than that.
I've managed to get 1400MHz @ 6-6-6-18/1.60v which I thinks quite good tbh, and according to Everest out-paces an tri-channel i7 965 set up @ 1333MHz.
It's just bugging me that it wont do 'low' timings that my old DDR2 Dominator RAM was pushing @ 1066

Anyone got any ideas or actually attained 5-5-5-15/18 w/ DDR3 <=1.65v ?

[matty-hodgson]

DDR3 is usually always 7-7-7-20 or higher. 1600MHz RAM surely won't be able to reach 5-5-5-15.
on my i7 system (sold it now) i had my 1333MHz RAM @ 1866MHz constantly stable and that was at 7-7-7-20. how about you just try and ramp up the MHz instead of lowering the latency? should come to the same effect?

good luck.

[Infinite]

The RAM I'm using is in the spec to the left and for the life of me I cant get to run @ 5-5-5-15/18.

It simply refuses to boot even @ 1066MHz (I've not tried 800) with 1.65v, obviously I don't want to be going any higher than that.
I've managed to get 1400MHz @ 6-6-6-18/1.60v which I thinks quite good tbh, and according to Everest out-paces an tri-channel i7 965 set up @ 1333MHz.
It's just bugging me that it wont do 'low' timings that my old DDR2 Dominator RAM was pushing @ 1066

Anyone got any ideas or actually attained 5-5-5-15/18 w/ DDR3 <=1.65v ?

Why do you want to make your DDR3 go at DDR2 speeds? Nostalgia?

[aidanjt]

Why do you want to make your DDR3 go at DDR2 speeds? Nostalgia?

That's what I was wondering. It's not as if memory latency is a big issue with current micro-architectures. Unless the OP has *specific* ultra-low-latency application requirements, then slowing down RAM access is only going to serve to hurt performance.

[Pob255]

Umm if you mean this stuff http://www.ocztechnology.com/product...triple_channel
Then it's 1600mhz 8-8-8-24 1.65v cas8 not cas6

[Zhaoman]

No I wouldn't expect DDR3 to do 5-5-5-15 because the cycles are shorter than DDR2. In fact Cas7 on DDR3 is comparable to 5-5-5-15 on DDR2.

Pulled straight from Wikipedia:

http://en.wikipedia.org/wiki/DDR3_SDRAM

"While the typical latencies for a JEDEC DDR2 device were 5-5-5-15, the standard latencies for the JEDEC DDR3 devices are 7-7-7-20 for DDR3-1066 and 7-7-7-24 for DDR3-1333.

DDR3 latencies are numerically higher because the I/O bus clock cycles by which they are measured are shorter; the actual time interval is similar to DDR2 latencies (around 10 ns). There is some improvement because DDR3 generally uses more recent manufacturing processes, but this is not directly caused by the change to DDR3."

[Terbinator]

I mentioned in my original post that i just found it really annoying that it wouldn't run @ 5-5-5-15. for final settings I'll probably try and stick to 7-7-7-20 at highest and maybe get to around 1500MHz for my 25/7 performance - who know's

like I say, I just found it weird it wouldn't run at the timings I mentioned

[jim]

maybe get to around 1500MHz for my 25/7 performance

I've always said there aren't enough hours in the day

[Terbinator]

In my life I decide how many hours there is

[BUFF]

I mentioned in my original post that i just found it really annoying that it wouldn't run @ 5-5-5-15. for final settings I'll probably try and stick to 7-7-7-20 at highest and maybe get to around 1500MHz for my 25/7 performance - who know's

like I say, I just found it weird it wouldn't run at the timings I mentioned

DDR2 wouldn't run at the latencies of DDR1 either ...
different thing, different parameters

[Terbinator]

DDR2 wouldn't run at the latencies of DDR1 either ...
different thing, different parameters

That's what I was initially getting at/after. Any suggestions for what the best combo would be? I assume I should be after the combination which offers the most bandwidth while staying under 1.65v

[kevpuk]

Pretty sure I read an article a while back (quite a while, think it was about DDR !) suggesting a nominal Mhz figure against a CAS latency or similar.....I believe it was around 4-4-4-xx being similar to 5-5-5-xx at +100MHz, but - unfortunately - cannot prove that out with said article.

I guess the thing to do is run a small suite of benchmarks with higher clock speed then lower latencies and see what brings best results forwhat you primarily use PC for ?

[CAT-THE-FIFTH]

The memory controller in the Phenom II tends to be prefer lower latencies though especially with games:
http://www.tomshardware.com/reviews/...ddr3,2319.html

[scaryjim]

Any suggestions for what the best combo would be?

Personally, I'd go back to the default timings and push them to as high a clock as they'll go.

As a guide, theoretical latency with 6-6-6 @ 1400 is the same as 7-7-7 @ 1633 and 8-8-8 @ 1866 (~4.3ns, I think...), but the bandwidth increases by 17% / 33% as you increase the clock rate. If you want to work out the actual latency for a given CL / Clock combination divide 1000 by the clock speed in MHz then multiply by the CL number - AFAIK real world performance is far more dependant on memory bandwidth that latency, though...

[hsbc]

In my life I decide how many hours there is

you are very lucky