Completely confused about memory speeds and timings

[OhNoPoPo]

Back in the day, there was one speed of RAM and it would work.

I have been searching and reading articles about what will work in a 975xbx (BadAxe) mobo with a Conroe chip -- apparently you can put 533, 667, or 800 speed RAM in there.

I am just confused at what benefit (if any) if I have an X6800 chip, no overclocking with faster RAM? What RAM should I get? And if I don't overclock, should I really get faster RAM?

 

[OhNoPoPo]

I see someone has posted almost the exact question as me just a few threads below:

http://forums.anandtech.com/messageview...atid=28&threadid=1922028&enterthread=y

Although he is planning to overclock. Do the recs hold true even without oc'ing?

 

[phile]

The memory speed you choose depends on how much you wish to overclock, and your board's support for various memory timings. For example, running your mem at DDR2-800 with stock FSB (266) would require the 2:3 FSB:MEM divider - 266/400 (DDR2-800 runs at a real clock of 400MHz and at 800MHz effective clock due to it being dual data rate memory). Let's say your board did not support memory dividers, you would be forced to downclock your mem to DDR2-533 - 266/266. Let's say you planned to run at FSB 333, you would have to run the mem at DDR2-667 to achieve the 1:1 ratio. Most people buying conroe chips are pairing them with DDR2-800 memory, which can be run 1:1 at FSB 400. The higher-end boards should have good support for memory dividers. Myself, I'm using a P5W DH and have achieved stability with both the 2:3 and 4:5 dividers. I expect the BadAxe is no different.

As for your specific situation, buying a x6800 and not overclocking, at least modestly, would be a sad waste. If I were you, I would go with a good 2GB kit of DDR2-800 and try for 400 FSB. If that isn't doable for you, you can always opt to use a memory divider at lower FSB, or just downclock the mem. Myself, I'm running my E6600 at FSB 333 with my DDR2-800 kit downclocked to DDR2-666, in order to run at 1:1. My other option at FSB 333 was to slightly overclock the mem to DDR2-833 and use the 4:5 divider. I benchmarked both configs and found essentially no difference in overall system performance.

This memory/fsb stuff is quite convoluted. I hope the above offers at least a modicum of clarity.

-phil

 

[OhNoPoPo]

Originally posted by: phile
The memory speed you choose depends on how much you wish to overclock, and your board's support for various memory timings. For example, running your mem at DDR2-800 with stock FSB (266) would require the 2:3 FSB:MEM divider - 266/400 (DDR2-800 runs at a real clock of 400MHz and at 800MHz effective clock due to it being dual data rate memory). Let's say your board did not support memory dividers, you would be forced to downclock your mem to DDR2-533 - 266/266. Let's say you planned to run at FSB 333, you would have to run the mem at DDR2-667 to achieve the 1:1 ratio. Most people buying conroe chips are pairing them with DDR2-800 memory, which can be run 1:1 at FSB 400. The higher-end boards should have good support for memory dividers. Myself, I'm using a P5W DH and have achieved stability with both the 2:3 and 4:5 dividers. I expect the BadAxe is no different.

As for your specific situation, buying a x6800 and not overclocking, at least modestly, would be a sad waste. If I were you, I would go with a good 2GB kit of DDR2-800 and try for 400 FSB. If that isn't doable for you, you can always opt to use a memory divider at lower FSB, or just downclock the mem. Myself, I'm running my E6600 at FSB 333 with my DDR2-800 kit downclocked to DDR2-666, in order to run at 1:1. My other option at FSB 333 was to slightly overclock the mem to DDR2-833 and use the 4:5 divider. I benchmarked both configs and found essentially no difference in overall system performance.

This memory/fsb stuff is quite convoluted. I hope the above offers at least a modicum of clarity.

-phil

I think I understand what you're trying to say. How stable will the system be if I push it to 400FSB? And is pushing the FSB considered oc'ing? (Sorry if that's a stupid question).

And what about all this stuff with memory voltages? I do NOT have a "spare" DIMM lying around just to boot up the first time and change stuff in the bios to get my system up and running! Will I be able to find 1.8v pc800 ram?

 

[phile]

Originally posted by: OhNoPoPo

Originally posted by: phile
The memory speed you choose depends on how much you wish to overclock, and your board's support for various memory timings. For example, running your mem at DDR2-800 with stock FSB (266) would require the 2:3 FSB:MEM divider - 266/400 (DDR2-800 runs at a real clock of 400MHz and at 800MHz effective clock due to it being dual data rate memory). Let's say your board did not support memory dividers, you would be forced to downclock your mem to DDR2-533 - 266/266. Let's say you planned to run at FSB 333, you would have to run the mem at DDR2-667 to achieve the 1:1 ratio. Most people buying conroe chips are pairing them with DDR2-800 memory, which can be run 1:1 at FSB 400. The higher-end boards should have good support for memory dividers. Myself, I'm using a P5W DH and have achieved stability with both the 2:3 and 4:5 dividers. I expect the BadAxe is no different.

As for your specific situation, buying a x6800 and not overclocking, at least modestly, would be a sad waste. If I were you, I would go with a good 2GB kit of DDR2-800 and try for 400 FSB. If that isn't doable for you, you can always opt to use a memory divider at lower FSB, or just downclock the mem. Myself, I'm running my E6600 at FSB 333 with my DDR2-800 kit downclocked to DDR2-666, in order to run at 1:1. My other option at FSB 333 was to slightly overclock the mem to DDR2-833 and use the 4:5 divider. I benchmarked both configs and found essentially no difference in overall system performance.

This memory/fsb stuff is quite convoluted. I hope the above offers at least a modicum of clarity.

-phil

I think I understand what you're trying to say. How stable will the system be if I push it to 400FSB? And is pushing the FSB considered oc'ing? (Sorry if that's a stupid question).

And what about all this stuff with memory voltages? I do NOT have a "spare" DIMM lying around just to boot up the first time and change stuff in the bios to get my system up and running! Will I be able to find 1.8v pc800 ram?

Increasing the FSB is the foundation of overclocking. The FSB is your real system clock, while the effective clock is the FSB quad-pumpd. So, with a real clock of FSB 266, your effective FSB is 1066. To calculate the CPU operating frequency, you multiply the real system clock (FSB) by the clock multiplier. I think the default clock multiplier for the X6800 is 11, so the stock speed of the X6800 is 266 X 11 = 2926MHz. Overclocking is essentially boosting the real system clock (FSB), which results in a higher effective system clock and CPU frequency. Unfortunately, it's not that simple. Raising the system clock requires more power, and thus you need to play with other settings, like vcore - voltage to the CPU. It can be a long process of trial and error, until you find the stability points for your setup. I'm pretty new to this stuff, as well, so I haven't done any hardcore overclocking. What you could do is find people with your exect mem/mobo/cpu setup and use try some of their stable overclocking configs. Don't a significant o/c like FSB 400 unless you know what you're doing. Typically, you have to work your way up to that kind of o/c.

As for memory issues, there are none that I know of with the BadAxe. The problem you mention is likely the issue with OCZ Gold DDR2 mem and P965 chipset based mobos. You should have no boot issues with any good kit of DDR2.

As for terminology:

PC2-6400 = DDR2-800
PC2-5400 = DDR2-667
PC2-4200 = DDR2-533

-phil

 

[OhNoPoPo]

So what it all comes down to is: buy faster memory for *possibility* of overclocking?

What if i'm set on not OC;ing? Will the 800 memory just become overpriced 533 then? Or will it still be faster?

 

[Baked]

Buy the RAM that's most expensive. Problem solved.

 

[phile]

Originally posted by: OhNoPoPo
So what it all comes down to is: buy faster memory for *possibility* of overclocking?

What if i'm set on not OC;ing? Will the 800 memory just become overpriced 533 then? Or will it still be faster?

First of all, the X6800 is a glorious waste of money unless you plan to significantly overclock. For 1/3 the price you can buy a E6600 which can be modestly overclocked to run at the same stock speed as the X6800. As for memory, I would go with PC2-6400 no matter your initial plans. It's not that much more expensive, and you'll be covered if you decide to o/c in the future. And, as I said, running DDR2-800 downclocked to DDR2-666 or DDR2-533 does not dramatically reduce overall system performance.

-phil