What is the deal with CAS latency and AMD64s?

[fishstickz]

As the title says, what is the deal with CAS latency with new 64s? Does it matter?

I have seen people going both ways, saying it is just as important as before or less so- people emphasizing speed and capacity as being greater factors in RAM performance.

If it matters less, does it give you the oppurtunity to cheap out on RAM for new AMD64 systems?

Thanks

 

[MobiusPizza]

2 and 2.5 CAS setting doesn't matter much. CAS setting of 3 lowers performance by around 5% or more
It is generally recommended to not to go higher than 3 CAS

Capacity currently 1GB is the popular config. If you are heavy on photo and video editing, 2GB or even more is recommended.

Overclocking A64 yeilds much more performance gain, even if the memory speed is not 1:1 but on a divider.
Generally you want as high CPU frequency as possible, then as low timing as possible, then is the memory frequency

CPU Speed >> Memory timing > Memory frequency

 

[fishstickz]

Thanks for your help. Unfortunately, the Mobo I have is devoid of OC features, but it doesn't matter much to me to push my Winny beyond its specs.

I run my Corsairs at 2.5 and I'm very happy with the performance, I was just curious.

Thanks for the help.

 

[hurtstotalktoyou]

Originally posted by: AnnihilatorX
2 and 2.5 CAS setting doesn't matter much. CAS setting of 3 lowers performance by around 5% or more
It is generally recommended to not to go higher than 3 CAS

Just to be clear, the performance difference between CAS-2 and CAS-2.5 is about the same as between CAS-2.5 and CAS-3. http://www6.tomshardware.com/motherboard/20040119/index.html

If you can find a great deal on CAS-3 memory, go ahead and get it. You can always boost performance in other ways.

Capacity currently 1GB is the popular config. If you are heavy on photo and video editing, 2GB or even more is recommended.

By you, maybe. 2GB is overkill for a mainstream machine, regardless of the applications you run. The reason for this is that it costs about $100 or so to get that extra gigabyte, for a performance gain of 2% or so. For $100, you can get a 3700+ instead of 3500+, or a 3500+ instead of 3200+, etc., and you'd see performance gains of 10% or more. Only when you've got a 3700+ or 3800+ does 2GB become even remotely reasonable--and even then it's a tough call.

Overclocking A64 yeilds much more performance gain, even if the memory speed is not 1:1 but on a divider.
Generally you want as high CPU frequency as possible, then as low timing as possible, then is the memory frequency

CPU Speed >> Memory timing > Memory frequency

Close. More like this....
CPU speed > memory frequency > memory timing

 

[fishstickz]

2GB is overkill for a mainstream machine, regardless of the applications you run.

2GB is overkill for my 3200+ Winchester?

I don't have the 2GB listed in my sig yet- I was going to order it later today- I have 1GB of some the same type of Corsair RAM, which I was going to sell once I got the 2GB.

Are the performance gains really going to be that minimal, in the 2% range? If that is the case, then I'm going to save my money! I do lots of RAM intensive apps (video editing is a big part of the time spent my comp) but if I don't need it, then I won't buy it.

I'd really appreciate your input on this...

Edit: Grammar and quote.

 

[IEC]

Originally posted by: fishstickz

2GB is overkill for a mainstream machine, regardless of the applications you run.

2GB is overkill for my 3200+ Winchester?

I don't have the 2GB listed in my sig yet- I was going to order it later today- I have 1GB of some the same type of Corsair RAM, which I was going to sell once I got the 2GB.

Are the performance gains really going to be that minimal, in the 2% range? If that is the case, then I'm going to save my money! I do lots of RAM intensive apps (video editing is a big part of the time spent my comp) but if I don't need it, then I won't buy it.

I'd really appreciate your input on this...

Edit: Grammar and quote.

And 64K of memory is more than *anyone* will ever use

I'm planning on getting 2GB for my next rig because 1GB is simply not enough playing the latest games or doing heavy video/photo editing - there is a noticeable difference with higher res textures and resolutions.

 

[PerfeK]

2GB will soon become the new norm. I'd give it 6-12 months.

 

[stonecold3169]

I just switched to 2gb up from 512 and the difference is amazing. You would be amazed at how much memory stuff uses when it has the room... by default, most programs try and not strangle your memory, so if you ahve 512mb they might take, say, 300mb to run (talking about world of warcraft). Now that I have 2gb, it jumps to about double that, and runs better even though it ran great before.

This is even more evident in some other applications.

 

[RussianSensation]

Answer
*Also click next for the benches on the 2nd page.

You can see for yourself if you feel the difference in memory speed or latency is worth the additional cost

In most cases DDR600 (ie FSB 1:1 cpu:ram), 3-5-5-10 memory was faster than 2-2-2-5 DDR400 on A64 in games. However, with all this in mind, once you increase the resolution and settings, memory latency or speed have no noticeable effect in the real world in games (since games become mostly graphics card limited). Some claim that faster memory latency makes the system feel smoother overall - this maybe so. Oftentimes you can find a sweet spot, like very cheap memory that can do 2-3-2-5 or 2.5-3-3. However, if you can save $50+ on memory, it is almost always better to invest it into a faster graphics card, cpu, or more memory for that matter.

 

[Suspicious-Teach8788]

3-5-5-10

well it surely wont be faster than DDR533 @ 2-2-2-5 with Redlines =P

But I know the extra money on ram really isn't worth it. 2gb vs 1gb is a different issue. IF you really need 2, then go ahead, but otherwise like the post above save for something else.

 

[fishstickz]

I see where this is going. I'm still leaning towards the 2 GB a little - the difference from 512MB to 1 GB is huge. I must be wrong in assuming a linear progression here?

I can't clock over DDR400 speeds on my motherboard, so anything faster isn't worth it. Is the extra gig still worth it in this case?

 

[fishstickz]

*bump*

 

[FreshFish]

Originally posted by: RussianSensation
Answer
*Also click next for the benches on the 2nd page.

You can see for yourself if you feel the difference in memory speed or latency is worth the additional cost

In most cases DDR600 (ie FSB 1:1 cpu:ram), 3-5-5-10 memory was faster than 2-2-2-5 DDR400 on A64 in games. However, with all this in mind, once you increase the resolution and settings, memory latency or speed have no noticeable effect in the real world in games (since games become mostly graphics card limited). Some claim that faster memory latency makes the system feel smoother overall - this maybe so. Oftentimes you can find a sweet spot, like very cheap memory that can do 2-3-2-5 or 2.5-3-3. However, if you can save $50+ on memory, it is almost always better to invest it into a faster graphics card, cpu, or more memory for that matter.

Wow, thanks for that link! I was about to buy some low latency RAM so I could overclock it and try to run it 1:1 with an OC'd Venice...but from looking at that, I think I might just buy some value RAM and use a memory divider...the performance difference was not worth the price difference at all, from looking at those benches. Thanks for saving me some $$

 

[hurtstotalktoyou]

Your best bet would be to find some benchmarks pitting a 1GB system versus one with 2GB. Blain (another Anandtech forum member) had run some of his own benchmarks, but he no longer has the results online. If I remember correctly, the performance differences were very small--about 2% or so. I PMed him to see if he still has his results, and I'll post them here if he does.

The whole issue here is money. A second gig of RAM will cost you about $100, yielding a performance increase of about 2%. Can you boost performance any more than that by spending your money on the CPU or hard disk, instead? Usually you can, which means that 2GB RAM is a bad idea in those cases.

 

[RussianSensation]

hurtstotalktoyou, true benchmarks show that 2 gig is not much of an improvement over 1 gig. However, many users have reported a benefit from 2 gigs in BF2. It'll at least boost the game's loading times and "exit" smoothness. There is certainly no rush to get 2 gig just yet, but it's much better to have 2 gigs for gaming than $250 2-2-2-5 1 gig ram in my eyes.

Also benchmarks are often misleading...here take a look at this:

World of Warcraft memory performance

From looking at these benches, it seems that 256mb is acceptable as it offers above 50 frames per second. Please see the video in the top right-hand corner. You will see a drastic difference between the 3 memory configurations that benchmarks were unable to capture.

 

[hurtstotalktoyou]

Here are those benchmarks Blain ran...

http://pics.bbzzdd.com/users/Blain/Benchmarks.jpg

 

[Sonikku]

Meh. This sucks. On the one hand I hear Athlon 64 likes two sticks of ram more then 4, yet I'm presented with getting corsair value ram with a latency of 2.5 for 2x512 (two sets of two sticks for a total of 2GB) or buying two single 1 GB sticks with a latency of 3 for a total of 2GB. Some people tell me my Venice 64 cpu is better off with only two ram sticks rather then 4, yet now I'm hearing 2.5 latency is better then 3 for normal operation.

 

[hurtstotalktoyou]

They make 1GB DIMMs, you know--even with low latency.

http://www.newegg.com/Product/Product.asp?Item=N82E16820145575

I'm not recommending those, but they do exist.

 

[Sonikku]

When I said corsair value ram, I did not mean 1 gig sticks of ram over the cost of $90.