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Asus P4PE & twinx2048 3500llpro


NeilF

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I'm overclocking my processor to a FSB of about 155, which means with the 4:3 ratio means a memory speed of about 413 (2*155*4/3).

 

So can I just plug in "TWINX2048-3500LLPRO XMS3500 2048MB 2-3-2-6-1T 2x184 DIMM Black XMS ProSeries" and off I go?

 

No compatability issues etc?

 

I'm no memory expert so sorry if this is a daft question!

 

ps: I'm currently running at a ratio of 1:1 which means I'm actually running my existing 2700 memory underspeed (310Mhz, 2x155).

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Due to the limitations of all of Intel's DDR1 chipsets (including yours), it is not recommended to run memory any faster than your processor's FSB by more than 33MHz. This means with a 155MHz FSB (QDR620), the recommended maximum memory speed is 188MHz (DDR376). In fact, your system will likely not run stably at memory clockspeeds above what your current memory speed is set at. As a matter of fact, that 4/3 divider is designed primarily for operating PC2100/DDR266 memory at 133MHz/DDR266 with a "400MHz" (100MHz actual) FSB processor.

 

And that's not to mention that the i845PE chipset officially supports only up to PC2700 DDR memory (this means an official maximum memory clockspeed of 166MHz/DDR333) - and it's a single-channel-only chipset, at that.

 

Therefore, the TwinX2048-3500LLPRO is overkill for your older Intel platform.

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Due to the limitations of all of Intel's DDR1 chipsets (including yours), it is not recommended to run memory any faster than your processor's FSB by more than 33MHz. This means with a 155MHz FSB (QDR620), the recommended maximum memory speed is 188MHz (DDR376). In fact, your system will likely not run stably at memory clockspeeds above what your current memory speed is set at. As a matter of fact, that 4/3 divider is designed primarily for operating PC2100/DDR266 memory at 133MHz/DDR266 with a "400MHz" (100MHz actual) FSB processor.

 

And that's not to mention that the i845PE chipset officially supports only up to PC2700 DDR memory (this means an official maximum memory clockspeed of 166MHz/DDR333) - and it's a single-channel-only chipset, at that.

 

Therefore, the TwinX2048-3500LLPRO is overkill for your older Intel platform.

 

Thanks for the reply... You'll have to bear with me here...

 

My bus is 155 so at 4:3... 155*2*4/3=413. Or is that wrong? So given the memory frequency can be set to 413, the nearest (faster) memory is surely PC3500 (433)?

 

Even at 5:4, 155*2*5/4=388, which surely would mean PC3200 (400) memory?

 

I've seen many people referring to using PC3200 & PC3500 on P4PE's I assume for this reason?

 

note: A certain memory company, when searching for the P4PE, lists PC3200 memory. Which I assume is because even at standard FSB rates (133), 2*133*4/3=355? Now add on some overclocking and you're well beyond PC2700, and surely even PC3200. Hence me asking about PC3500.

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Thanks for the reply... You'll have to bear with me here...

 

My bus is 155 so at 4:3... 155*2*4/3=413. Or is that wrong? So given the memory frequency can be set to 413, the nearest (faster) memory is surely PC3500 (433)?

 

Even at 5:4, 155*2*5/4=388, which surely would mean PC3200 (400) memory?

 

I've seen many people referring to using PC3200 & PC3500 on P4PE's I assume for this reason?

 

note: A certain memory company, when searching for the P4PE, lists PC3200 memory. Which I assume is because even at standard FSB rates (133), 2*133*4/3=355? Now add on some overclocking and you're well beyond PC2700, and surely even PC3200. Hence me asking about PC3500.

 

Sure, you can use such memory. But the farther away from synchronous you stretch your memory speed from, the less stable your system becomes. Therefore, you will get the most stable results on a 155MHz (QDR620) FSB by running your memory at exactly 155MHz (equivalent to DDR310).

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Sure, you can use such memory. But the farther away from synchronous you stretch your memory speed from, the less stable your system becomes. Therefore, you will get the most stable results on a 155MHz (QDR620) FSB by running your memory at exactly 155MHz (equivalent to DDR310).

 

Huh? Why on earth then would ASUS but the option in to run memory (at 5:4 & 4:3) if it was not stable and designed to do so?

 

Why wouldn't the system run smoothly with PC3500 (433) with my FSB at 155 and a Dram ration of 4:3? Isn't that why the option is there?

 

note: I'm currently running at 1:1 with PC2700 (333) memory.

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Huh? Why on earth then would ASUS but the option in to run memory (at 5:4 & 4:3) if it was not stable and designed to do so?

 

Why wouldn't the system run smoothly with PC3500 (433) with my FSB at 155 and a Dram ration of 4:3? Isn't that why the option is there?

 

Remember, that 4:3 DRAM:FSB ratio is originally intended for those people who have 100MHz (400) FSB processors to run PC2100 (DDR266) memory at the memory's full rated speed. Similarly, the 5:4 ratio is intended for 133MHz (533) FSB processor owners to run PC2700 (DDR333) memory at the full memory speed. (In both cases, the memory speed is only 33.3MHz higher than the processor's FSB speed.) But when you use a higher FSB and then use such divider ratios, you'll actually be stressing the motherboard chipset. Intel does not officially support asynchronous operation by greater than PCI bus rate (+/-33.3MHz). Any differential between memory and FSB speed of greater than +/-33.3MHz is beyond the official specs of Intel's DDR1 chipsets.

 

What's more, the Intel 845PE chipset (which is the chipset on your P4PE motherboard) does not officially support even PC3200 (DDR400) memory, let alone higher-speed memory. Its official memory support tops out at PC2700 (DDR333).

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Remember, that 4:3 DRAM:FSB ratio is originally intended for those people who have 100MHz (400) FSB processors to run PC2100 (DDR266) memory at the memory's full rated speed. Similarly, the 5:4 ratio is intended for 133MHz (533) FSB processor owners to run PC2700 (DDR333) memory at the full memory speed. (In both cases, the memory speed is only 33.3MHz higher than the processor's FSB speed.) But when you use a higher FSB and then use such divider ratios, you'll actually be stressing the motherboard chipset. Intel does not officially support asynchronous operation by greater than PCI bus rate (+/-33.3MHz). Any differential between memory and FSB speed of greater than +/-33.3MHz is beyond the official specs of Intel's DDR1 chipsets.

 

What's more, the Intel 845PE chipset (which is the chipset on your P4PE motherboard) does not officially support even PC3200 (DDR400) memory, let alone higher-speed memory. Its official memory support tops out at PC2700 (DDR333).

 

Note: I've had my figures round the wrong way in previous posts! I meant my board has 1:1, 4:5 & 3:4...

 

So if I bought some PC3200 memory, I could try running it at 4:5 (155*2*5/4=388) (or even 3:4). And if I hit any problems I could always revert back to 1:1?

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