Computer Memory

gco

gco

Veteran
This is only marginally related to Vegas -- has to do with a system I am trying to configure for editing with Vegas and not Vegas itself. The Cafe has no interest so I am trying here.

Can anyone tell me if choosing a 533 Mhz or 667 Mhz memory matters?
According to videoguys, the ideal or optimum rated memory speed is 1/2 the front side bus speed of your processor. Seems to make sense. Following that, a processor with an fsb of 1066 Mhz would require a memory rated at (1/2 of 1066) 533 Mhz. Accordingly, a 1333 Mhz fsb would require 667 Mhz rated memory.
Here's the catch. After finally getting through to a human at Dell tech, I am told one is optimum but either will work. He couldnt really tell me why. Actually I wasnt understanding much of what he said due to his accent.

So my question is, if I have a processor with an fsb of 1066 and use a higher rated memory of 667, will the actual memory access speed still be (1/2 of 1066) 533 regardless of the fact that the memory is rated higher? To put it another way, will using a memory that is rated higher than what is required, affect performance?

Any ideas would be greatly appreciated.
 
It entirely depends whether your motherboard will support it. If you run 667MHz ram at 667MHz then this will clearly be preferable to 533MHz. Your motherboard 'might' only be able to run the 667 at 533, so do check.

Strictly speaking, 1066MHz ram would be better still-- if the ram runs at the same speed as the fsb then that would be ideal ... the CPU/FSB/RAM all running at the same clock would be truly optimal (as in the PS3), HOWEVER!

When discussing subtlety faster system memory for 'not so subtle' price differences, you are firmly into the territory of "the law of diminishing returns". If the price premium for 667 is small then faster is preferred, but the actual performance difference will range from "very small" to "no difference at all", depending on the specific tasks that you ask of your system. There are certain operations (such as massive database i/o operations) which will specifically push your ram and reveal a small % difference, but I would suggest that you wouldn't get your money's worth for standard video work! 533MHz is perfectly adequate.
 
Ok, I'm beginning to believe the processor I want will only run a 667 at 533 regardless. I guess that is just the way DDR2 architecture works. If that is correct and either memory rating will work as you and Dell tech suggest, then I just dont know why others would say 533 is "optimal" for a 1066 fsb. Maybe for reasons of cost only, dont know. I suppose I'll just pick the 533 and be done with it if there is no point in paying extra for a higher rating.

Your point on diminishing returns is well taken. Definitely a worthwhile consideration.
Thanks for the feedback!, it helps.

gco
 
The 533 might run faster if it has lower memory latency.

To use a car analogy (hopefully this makes sense):
Memory latency is like acceleration (or cornering).
The 533 mhz versus 667 mhz is like driving speed (or top speed the car can go). The 667 mhz RAM is rated to run at the higher speed; however, you only see advantages if you drive that fast.

One of the tradeoffs with RAM is that you can't have both low latency and high bandwidth. So the 533 RAM might be potentially faster.

Sometimes, two speed grades may just be the same RAM chips since it's cheaper to tool the production line for the higher speed RAM.

2- Hardware review sites like xbitlabs.com do reviews of RAM with benchmarks.

3- None of this really matters. The speed differences are fairly insignificant (a few percent), and will be pretty meaningless when computers get magnitudes faster in only a few years.

The one thing that does make a difference is dual channel operation. To allow this to happen, always use pairs of RAM, and identical RAM.
 
Glen >
Meaning if i wanted 2 gb ram its better to always go half. 1gb x 2 chips right ?
1 gb ram would mean 512 x 2 chips. Same company, clocking speed etc. Will vegas use up to 2 gb ram or 1gb only. Or in other words will there even be a noticeable difference ?
 
For a total of 2GB RAM, I would go with 2 X 1GB chips since it's cheaper and faster than 1 X 2GB chip.

If you multi-task a lot, then you may get a little smoother performance with 2GB RAM. 1GB should be fine too though.
 
Once again, this website is proving to be gold mine.
Glenn, thank you so much.
I checked out xbitlabs.com and sure enough they have an article right on point.
The processor they were using for their benchmark tests happened to be the same one I am considering--a Core2Duo E6700--go figure.
Their main point is that there is no appreciable benefit to anything above 533 in most circumstances unless you are overclocking.

"The previous section may give you an impression that Core 2 Duo systems do not in fact need fast memory. Using higher-frequency memory modules makes the system costlier, yet doesn't lead to any significant performance increases. This is true, in part: memory faster than DDR2-533 can only provide a maximum of 5% performance growth in a majority of widespread applications. The problem is in the front-side bus which is only clocked at 266MHz as yet."

Not sure why they are saying a 1066 fsb is "clocked" at 266 but regardless, the point is taken.
 
For advertising reasons, the advertised FSB speed is 4 times that of the actual FSB speed. I can't remember the technical reason that sort of backed it up.
 
Good to know. I'm not surprised.
Probably the difference between theoretical calculated and actual bus speeds. Kind of like advertising a stereo system using watts peak instead of watts rms. Doesnt have to be realistic, just a bigger number. Go figure.
 
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