DDR vs DDR2 Latency, How Cycles Work, and Dual Channel Marketing

I’ve noticed one thing on the Internet, that stands out above almost all others: most people on the Internet have no clue what they are talking about. Case in point, a lot of ricers and gamerz like to say that DDR is lower latency than DDR2 because DDR2 takes more cycles to do things; except they forget one important thing: cycles are not a measurement of time, they are a measurement of iterations.

That said, there is only one case where DDR actually manages to be lower latency than DDR2 (and this doesn’t mean it has higher performance, or effects benchmarks in any measurable way in favor of DDR), and that is with DDR400 memory vs. DDR2-400 memory: latency is theoretically lower, but you pay a penalty for giving up DDR2’s larger prefetch buffer and better power efficiency. Also, no one actually uses DDR2-400 memory, only 667 and 800. DD2-800 compared to DDR400, latency ends up being similar in impact, and the actual performance is at least twice as much as DDR400, probably even more.

Another thing people say is that DDR2 is slower because it takes more cycles to do things. Yet another thought that hasn’t been fully thought out, and in a similar manner to the whole latency problem (infact, they are directly related; faster timings usually decrease latency across the same memory archetecture). As I said earlier, cycles do not measure time; however, cycles combined with cycles per unit of time measure time. DDR2 in most, if not all, situtations simply performs better.

So, to anyone out there that says that DDR2 is a step backwards: You’re an idiot.

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Published September 18th, 2006


75 Responses

Nope, it doesn’t make sense. Especially since modern ATX power supplies are always on anyhow. It sounds like your PSU and/or your motherboard has either been damaged or was already defective.

Yeah, but come tho think of it, using common sense….then only thing that would turn on my system w/o me hitting the power button would be my power supply with some extra built up energy right? Does that seem to make any sense??

Can’t help you there… try buying a PC Power and Cooling PSU next time, they aren’t retarded enough to split the 12v rail into four.

Hey, sorry this is off topic but it is urgent. I just built my new computer and it worked fine, i installed drivers and everything worked….then i turned it off and unplugged it and installed a new case fan and then re plugged it into my surge protector and turned on psu and the fans started flashing cause they have leds and wud start and stop and i even unplugged the new fan but the same problem occured. For reference, I have an ocz 600w psu with quad 12v rails and its brand new!

kyle, as long as the ram is the right kind, it should work fine. You shouldn’t have issues as its the right type.

No, I don’t have xfire.

I just purchased ram and a motherboard only to realize that the ram was not on the memory support list for the motherboard. I have not yet build my system but should I be worried about issues? Also, do you happen to have xfire or aim?

Assuming its at least 1000 watts, you may find yourself short on amps. I do not like dual rail designs, and only buy power supplies from PC Power and Cooling.

Do to the occasional improper design, its possible to have one rail unloaded, and the other one with the entire machine’s load, thus in your case, you’d have 18 amps total.

That said, dual rail designs are inefficient, badly designed, and almost lying but not enough to sue them over.

Go out and buy yourself a real PC Power and Cooling PSU at 1000 watts and you’ll be fine.

This is very off topic but you seem to know your stuff so if my power supply has 36 amps on the 12v rail (18 on 2 of them) would it be enough for a single hard drive, 8800gtx and quad core assuming that wattage is not an issue.

The fastest speed of DDR2 your board supports.

my motherboard supports ddr and ddr2 which should i be using for better performance and speed??

If the CPU’s FSB exceeds 800mhz, yes, other than that extensive testing would be needed to prove that.

And would you say that difference is noticeable?

A maximum of 33% faster. Its simple math, (((faster speed)/(slower speed)-1*)100).

Yes, but assuming the motherboard can support it, how much faster would ddr2 1066 be than ddr2 800?

It depends on your motherboard. Most do not support speeds faster than 800. So, if your mobo doesn’t support that speed, it’ll just run the memory at the fastest speed it does support.

Hey, I am going to buy a new system soon and it seems as though ddr3 will be way too expensive for me. However, when it comes to ddr2 ram is ddr2 1066 a lot better than ddr2 800 for the price? I also heard that 1066 is over clocked so would it still be ddr2 1066 by default when I put it in my pc? Thanks

Well, there is a slight problem with your argument. Under the original DDR2 specification, 800 was the maximum, under the new specification 1066 is the max; so, taking that into account DDR2-1333 will beat DDR3-1333 in the same way DDR533 (it does exist, and is also out of spec) will beat DDR2-533.

As with my original argument of DDR2-800 > DDR400 even though their latency is the same, DDR3 probably (as in, I don’t know yet, DDR3 isn’t out in full force yet) will come out in speeds much faster than 1333, and normal 1333 will have much lower CAS ratings.

So, basically, my advice is wait until AMD and Intel machines with DDR3 are common before judging DDR3.

ok, ddr3 ram is finally out. As of right now all i can find is 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) with 9 9 9 24 timings and cas latency 9.

How is this better than ddr2, which can get almost up to ddr2 1333, when its latency is lower than that of ddr3?

I answered this question earlier in the comments. It should be out late this year, or early next year, and it should be affordable 6 months after that.

Hey, do you know when they will have ddr3 ram out on the market? thanks.

Basically, latency is how long it takes from the request from your memory controller to reach your memory, and your memory to send the request back to your memory controller.

DDR2 takes twice as long to accept and send a request than DDR, so, theoretically, with DDR2 and DDR memory running at the same speed, the DDR memory will perform better.

The bottom line is, the test is flawed because most people use DDR2-800 and not DDR-400; this basically means latency hasn’t increased, but you can now issue twice as many requests.

I don’t doubt benchmarks say DDR2-800 is three times faster than DDR: you’re getting performance out of better designed CPU prefetches, CPU cache design. and memory controller design

I expect DDR3-1600 to perform twice as well as DDR2-800 due to the fact latency has increased 2x again but bandwidth has increased 2x as well.

oh n pat, i just read what i said and i made my point unclear so could u wrap things up for me n make it clear to the bozos who say ddr2 is a step back, im sure you understand what i was tryna stress, its all very logical, remember the cooler Q too please!!!!

hey another out of the topic Q if you dont mind please? but is the zalman flower cooler at 18DBA to 27 DBA quiet? or rele Quiet, im considering it over more expensive water cooling setups, i wnt a dead silent pc as mine is a media centre pc using athlon64 x2 which sounds lika hoover making hearing movies impossilbe (slight exageration)
oh yeah and btw ur right about what u say about dd1 vs ddr2, latencies is the time from the request from data to the time where the first bit is accessed, but higher frequencies is the time it takes for high bursts of data to be loading into memory, so let me latency is the time from when data first requests memory to the first bit being accessed whils t frequency is more of an advantages when it comes to burst of data, like in games, applications and so on, my point is, everyt software you use will benefit from dd2 over dd1 considering the dd2 memory you use is at least a 533mhz + from the dd1 400mhz

iv seen benchmarkings that show that ddr2 800 is three time better perfomring than dd400 but im not sure how authentic this review was…any1 got any ideas?


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