latency on ddr3

[Shambles1980]

I noticed that latency on ddr3 seems to be quite high compared to what i was used to on ddr2.
Is this across the board or are there high performance ddr3 with good 7-7-7 or 5-5-5 latency as standard?
the lowest i can seem to find is 9-9-9 Which to me seems a bit slow..

 

[LaytonJnr]

Hello,

Generally when you have to overclock memory, you sometimes have to increase the latency timings. The DDR2 had very low comparative memory clocks, therefore was able to have much lower latency timings - I think the maximum was something like 1066MHz (could be wrong). At the moment, most DDR3 RAM have 1333MHz clocks minimum, and therefore the CAS latency is much higher because the memory clock is higher.

I will admit, I'm no expert, so this could be wrong.

EDIT: A quick bit of research indicates that there are some lower memory clock DDR3 RAM that have 5-5-5 / 6-6-6 / 7-7-7 timings, but perhaps because of their low memory clock (which is becoming increasing less compatible with newer motherboards), there aren't many that are available to buy retail.

Layton

 

[Aquinus]

I think a quote off Wikipedia might clarify things, generally speaking though, @LaytonJnr is correct.

Note: Memory bandwidth measures the throughput of memory, and is closely related to memory timings. It is possible for advances in bandwidth technology to have an undesirable impact on latency. For example, DDR memory has been superseded by DDR2, and yet DDR2 has significantly higher latency at the same clock frequencies. However, DDR2 can be clocked faster, decreasing its cycle time. Now DDR2 has been superseded by DDR3, and the trend of a higher latency coupled with a higher clock speed has continued.

Increasing memory bandwidth, even while increasing memory latency, can improve the performance of a computer system with multiple processors, and also systems with processors that have multiple execution threads.

 

[TRWOV]

I noticed that latency on ddr3 seems to be quite high compared to what i was used to on ddr2.
Is this across the board or are there high performance ddr3 with good 7-7-7 or 5-5-5 latency as standard?
the lowest i can seem to find is 9-9-9 Which to me seems a bit slow..

Standard DDR1 memory went from 2-2-2-6 (100Mhz) to 3-4-4-8 (200Mhz). As noted by Layton, higher speeds seemly need looser timings although you might find golden samples from time to time that can take extra low timings.

 

[Shambles1980]

just noticed that 4gb 1333 ddr3 is actually slower than my old 4gb 800mhz ddr2 was @800mhz, i assume this would have to be because of the timings given that its quite a lot faster in terms of mhz.
maybe they have 1600mhz 6-6-6 ram some where, because i dont see much point in this 1333 stuff if its slower than ddr2 800.
what gets me though is the timings on my ddr2 could stay at stock even when i oc'd to 1000mhz so i dont see why 1333 would need such slow timings. 7-7-7 at 1600 i could understand. but 9-9-9 at 1333 seems a bit rediculous..
(my old ddr2 used to be 5-5-5-15 and could do that at 1000Mhz)

-=edit=-
ok. so i went off to find 7-7-7 1600mhz, and it seems they are out there.
2GB CellShock DDR3 PC3-12800 1600MHz (7-7-7-14) Dual Channel kit
thats a pitifull 2Gb but i assume there must be 8/16gb kits too.

i guess its not all bad then as 7-7-7-14 seems like nice latencys to me. i wonder why 9-9-9-21/24 is the standard it just seems like deliberatly slowing down the system. and making ddr3 look bad compared to ddr2 at almost 1/2 the speed.

 

[TRWOV]

DDR2-800 CL5 indeed has faster access times than DDR3-1333 CL9 but bandwidth is 10% more. It's a trade-off.

 

[URBAN303]

I noticed that latency on ddr3 seems to be quite high compared to what i was used to on ddr2.
Is this across the board or are there high performance ddr3 with good 7-7-7 or 5-5-5 latency as standard?
the lowest i can seem to find is 9-9-9 Which to me seems a bit slow..

okay double post so my answer is here > http://www.techpowerup.com/forums/t...ry-benchmark-here.186338/page-16#post-3116074

But continue in this post for Lantency it's better

 

[LaytonJnr]

From what I've seen from the early DDR4 press releases from different companies, the initial set of DIMMs are set to have higher CAS latency than DDR3 at the lower end of the frequencies (but lower voltage), however it seems the minimum frequency is now 1600MHz for DDR4 (but this may be wrong), and that later released DIMMs in the future will have much higher frequencies (up to ~4266MHz). Of course these higher frequencies will have higher CAS latency.

So at the moment, for 1600MHz, DDR3 RAM looks faster due to its lower CAS latency, but for the higher frequencies, DDR4 will possibly be faster.

Layton

 

[Tatty_Two]

Basically there is a point of gain when evolving from DDR2 to DDR3, at a guess it will be similar with the move to DDR4, it's always a balancing act between bandwidth and latency, the secret with DDR3 is getting that balance and therefore point of gain optimised in your individual system, one of the great things with DDR3 as opposed to DDR2 is the lower voltage ratings, for example my memory is rated at 2133mhz CL11 at 1.5V. they will actually do CL10 at that stock voltage, however I can run them at CL9 with 1.58V and should I choose, I can go 1600mhz at CL7 @ 1.6V, a level of flexibility (sometimes platform dependant I appreciate) that DDR2 just couldn't really give you.