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General Question On Latency

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bobad

Member
Joined
Apr 19, 2004
Location
Louisiana
As you can see from my sig, I need to swat my RAM bottleneck.

I've been studying up on RAM specs. The slower low latency stuff (2 or 2.5)is more expensive than the faster stuff with a little higher latency (3).

My question is, would I gain more by buying say PC4000 3-3-3, or PC3200 RAM with 2-2-2? What advantages and disadvantages to each?

I forgot to mention my main board. Will it take advantage of the highest speeds and /or latencies of the best RAM, or would my money be wasted on it?

Thanks,,,
 
if you buy low latency PC3200 RAM you can clock it higher than high latency RAM. Ie, you buy 2-2-2 PC3200 and run it at 275 3-3-3, while the PC3200 3-3-3 you can only run at 230 3-3-3
 
You can go either way. If you run good PC3200 you will operate in 5:4 mode to slow the ram to its 400-440MHz sweet spot. If you use good PC4000+ you will run 1:1 mode and hopefully 500+MHz on the ram. 1:1 mode is faster, which makes up almost all the benefit of the faster timings the 3200 may allow. I still prefer a 5:4 2-2-2-5 result over a 1:1 3-4-4-7 one, but the difference is very slight and may reverse itself depending on the exact application run.

I use the Abit AI7 mb, which allows 3.21V on the memory. I also have some good PC3200 BH5 memory. I chose to run a 250fsb so that the 5:4 mode would slow my memory to 400MHz. I then bought a cpu proven stable at 250fsb. I enjoy the resultant 2-2-2-5 timings and high level of GAT that result. My memory performance is excellent even only running 400MHz on the memory clock. And it only takes 2.8V to do it.

I alternatively could have bought some newer PC3200 ram like the new Corsair 3200XL (Samsung TCCD chips) or some decent PC4000 ram (Hynix DT-43) and attempted to run 1:1 mode. This would have likely run easily at the resulant 500MHz on 3-4-4-7 timings (maybe 2.5-4-4) on 2.8V. Application performance will vary little, but calculation intensive apps like folding or SETI may like the low latency 5:4 route better.
 
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Well, now I'm really confused.

Both replies make a lot of sense, but seem to disagree a little on the face of it.

One post seems to say that low latency is mainly good for getting a good RAM overclock out of slower RAM. Another post seems to say that running tight timings is actually better than getting the highest RAM overclock.

I suppose it's possible that both approaches can get good results, depending on the benchmark you use.
 
larva said:
You can go either way. ...

Application performance will vary little, but calculation intensive apps like folding or SETI may like the low latency 5:4 route better.

I don't know how much more clearly I can say it... Sorry for throwing in those confusing details along with the above statements.
 
klingens said:
if you buy low latency PC3200 RAM you can clock it higher than high latency RAM. Ie, you buy 2-2-2 PC3200 and run it at 275 3-3-3, while the PC3200 3-3-3 you can only run at 230 3-3-3

The way to avoid confusion here is to ignore this one. He's talking about PC3200 2-2-2 rated ram versus PC3200 3-3-3 ram, something completely immaterial to the question you asked.
 
larva said:
The way to avoid confusion here is to ignore this one. He's talking about PC3200 2-2-2 rated ram versus PC3200 3-3-3 ram, something completely immaterial to the question you asked.

Well, that's pretty much what I WAS asking.

I would like to know whether it makes more sense for my board to get fast, higher latency RAM or slower but lower latency RAM. (assuming the prices are fairly equal, and assuming my board can fully utilize the performance)

Thanks,,,
 
bobad said:
My question is, would I gain more by buying say PC4000 3-3-3, or PC3200 RAM with 2-2-2? What advantages and disadvantages to each?

No, you asked about PC4000 3-3-3 vs PC3200 2-2-2 ram. If you buy PC3200 ram, it had better be really good stuff and thus will not be rated 3-3-3.

Whether latency matters or not in a general sense depends on what application you judge by. It is generally only a small factor, but some apps will respond more greatly to it. But you asked about PC4000 vs PC3200, and that is the proper question here. No reason to put up with slow timings and PC3200 clock speeds.

Honestly, re-read your above question directly quoted above and my original response. I directly answered the exact question you asked in as much detail as I could. I honestly don't know what else to say. It's all there.
 
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