Just A Fantasy Theory!

bigfoot · Apr 14, 2004

An oddball idea hit me the other day and I thought I'd share it w/ everyone, even though it is stupid. I don’t have the stuff to try it out but maybe someone can tell me why it won’t work.

Here's the question I was pondering, how come AMD Athlon XP's can’t use something like "800FSB" such as Intel's, just 400x2 though.

Here's what I thought of, the Athlon bus since the very beginning of the architecture has been a 64-bit DDR like bus, but now-a-days there's duel-channel DDR chipsets giving it 128bit memory bus, now what good is an 128-bus if the cpu only has a 64-bit bus.

Now, since nForce's have a locked PCI-clock, what would happen if you used the 2-1 memory speed setting with DDR400 memory, I doubt this is even theoretically possible, but couldn't you set a literal 400Mhz FSB w/ 200Mhz Duel-Channel RAM, then there would be a real match between the memory bus and the cpu bus, except the memory system would have to be seriously re-tuned so that it could sync up.

hafa · Apr 14, 2004

bigfoot said:
Now, since nForce's have a locked PCI-clock, what would happen if you used the 2-1 memory speed setting with DDR400 memory, I doubt this is even theoretically possible, but couldn't you set a literal 400Mhz FSB w/ 200Mhz Duel-Channel RAM, then there would be a real match between the memory bus and the cpu bus, except the memory system would have to be seriously re-tuned so that it could sync up.

Look at the sig. I'm running my mem timings at 5-2-2-2...I think almost everyone who has a decent O/C is running a synchronous FSB...This is kind of old hat already.

bigfoot · Apr 14, 2004

I know that talking about nForce 2's is a really old topic, but I still wana know how come all the right things are there, but it's impossible to run the FSB @ 400Mhz ???

Silent Frog · Apr 14, 2004

Hey bigfoot, in your sig it says you run a A7V333. I have one with the 1.7 BIOS and I can't seem to set the CPU speed to Manual with out it saying "System failed start up due to OCing" I think thats the words, dunno. But anyway. I run a Palomino 1800XP, have you come across this?
I can't even make it run 133x11.5 on the manual setting, have to use either 1533 or 1150 settings, also I can't use 1909 setting I got with the BIOS update.

bigfoot · Apr 14, 2004

I hate that mobo cuz I F*** something up anytime i touch the jumpers and it has like a hundred of em! I'm betting there's something wrong with your jumper settings, you might wana whip out ur manual and go over the jumpers with a fine tooth comb

Silent Frog · Apr 14, 2004

Thx, I'll give it a go... I would love a A7N8X right about now :|

Silent Frog · Apr 14, 2004

Oh, and one more thing.. Do you worry about running your PCI and AGP at higher MHz? or doesn't it matter that much? Thx

bigfoot · Apr 14, 2004

Dont wory about that, u wont damage anything cuz of that, even though i've never managed to do it with this board, people say u can corrupt data on ur hard disk by making it run too fast, but like i said, i've never seen it happen

hafa · Apr 14, 2004

bigfoot said:
I know that talking about nForce 2's is a really old topic, but I still wana know how come all the right things are there, but it's impossible to run the FSB @ 400Mhz ???

It may be that there is a misunderstanding here regarding FSB and DDR; A DDR (double data rate) interface runs at an "actual" fsb of 1/2 the "stated" speed. i.e., if your FSB is 200MHZ, then it's actually 400 MHZ with DDR; 200MHZ on the rising and 200MHZ on the falling memory clock cycle.

Hope this helps clarify things.

Captain Newbie · Apr 14, 2004

hafa said:
It may be that there is a misunderstanding here regarding FSB and DDR; A DDR (double data rate) interface runs at an "actual" fsb of 1/2 the "stated" speed. i.e., if your FSB is 200MHZ, then it's actually 400 MHZ with DDR; 200MHZ on the rising and 200MHZ on the falling memory clock cycle.

Hope this helps clarify things.

Not quite, but you're close. Why it's called DDR is because the components can transmit on both the rising and falling edge of the clock cycle.

But whatever. I disagree with Intel and AMD branding their FSB's at obscene speeds (800, 533, 400 etc.) because it is misleading and confusing, and a little unfair to AMD...

Freddie · Apr 14, 2004

Captain Newbie you are wrong there, it does not rise and fall on clock cycle but on the voltage. It sends data when the voltage is rising and when it is falling, that is why regestered DDR is sometimes needed. As when your comp has a lot of ram it causes the northbridge to get loaded causing the voltage to rise and fall slower. However the northbridge tries to drive the siiignal that is not yet stable, as the voltage is too high/low.

bigfoot · Apr 14, 2004

I understand almost exactly DDR works, but what I mean is 400Mhz LITERALLY, u can call it DDR800 if you wana.

bigfoot · Apr 14, 2004

I disagree with Intel and AMD branding their FSB's at obscene speeds (800, 533, 400 etc.) because it is misleading and confusing, and a little unfair to AMD...

Yea, it is a little unfair,(except now when AMD can say, look I seriously got an 800Mhz-bus, and soon to be 1Ghz) but it isn't exactly lying though, considering that the P4 has a 128-bit DDR bus between the CPU and chipset, and that the Athlon XP is stuck with a rather dated 64-bit DDR bus. That means that the theoretical throughput for a P4 bus @ 200Mhz is 6.4Gb's while the Athlon XP's maximum theoretical throughput is stuck @ 3.2Gb's @ 200Mhz

That explains the P4's memory scores of 5+ Gb's while the Athlons is never higher than 3.2Gb's even w/ duel-channel RAM!

That’s also why I wonder how come you cant run the CPU's bus @ 400Mhz(800DDR) w/ Duel Channel DDR @ 200Mhz (400DDR), If it were possible, then at least the Athlon could have the same bus bandwidth as the memory does, then if the memory controller was designed to be able to sync up w/ the CPU bus somehow. Like @ every other cycle it can switch between RAM, so it can Read/Write on every cycle too.

NOW, I still wana know why it's impossible to run the CPU bus @ 400Mhz, a REAL 400Mhz.

Captain Newbie · Apr 14, 2004

Freddie said:
Captain Newbie you are wrong there, it does not rise and fall on clock cycle but on the voltage. It sends data when the voltage is rising and when it is falling, that is why regestered DDR is sometimes needed. As when your comp has a lot of ram it causes the northbridge to get loaded causing the voltage to rise and fall slower. However the northbridge tries to drive the siiignal that is not yet stable, as the voltage is too high/low.

<--- Needs to read his DDR spec more...but isn't that the same as executing a command on the RISING and FALLING edge of the clock signal?

Whatev.

Edited to read "rising and falling" instead of rising and leading...stupid me.

theguywiththeha · Apr 14, 2004

i think he is saying he wants to know why you cant run a athlon xp at 400mhz x2=800ddr to = the 200mhz x 2 ddr dual channal with would be like having pc800 ram 6.4gbs so then it would be like if the cpu was sync with the ram because the cpu isnt dual channal so lets call it 400x2 and 200x4 man i suck at explaining stuff like this i get funny looks from ppl i try explaining stuff to...lol but yea i tryed

dippy_skoodlez · Apr 14, 2004

Freddie said:
Captain Newbie you are wrong there, it does not rise and fall on clock cycle but on the voltage. It sends data when the voltage is rising and when it is falling, that is why regestered DDR is sometimes needed. As when your comp has a lot of ram it causes the northbridge to get loaded causing the voltage to rise and fall slower. However the northbridge tries to drive the siiignal that is not yet stable, as the voltage is too high/low.

Thats the same thing.

dippy_skoodlez · Apr 14, 2004

bigfoot said:
An oddball idea hit me the other day and I thought I'd share it w/ everyone, even though it is stupid. I don’t have the stuff to try it out but maybe someone can tell me why it won’t work.

Here's the question I was pondering, how come AMD Athlon XP's can’t use something like "800FSB" such as Intel's, just 400x2 though.

Here's what I thought of, the Athlon bus since the very beginning of the architecture has been a 64-bit DDR like bus, but now-a-days there's duel-channel DDR chipsets giving it 128bit memory bus, now what good is an 128-bus if the cpu only has a 64-bit bus.

Now, since nForce's have a locked PCI-clock, what would happen if you used the 2-1 memory speed setting with DDR400 memory, I doubt this is even theoretically possible, but couldn't you set a literal 400Mhz FSB w/ 200Mhz Duel-Channel RAM, then there would be a real match between the memory bus and the cpu bus, except the memory system would have to be seriously re-tuned so that it could sync up.

Lemme try to keep this straight this time. I've thought about that too. Intels FSB is 200x4, 4x a clock cycle, making it 800. AMD's is only 2 for the AXP. The raw speed itself, for a NB would probably an issue there, and we dont have any DDR running 800mhz. Otherwise, im sure it could be done if the CPU wouldn't puke on you from the amperage change, if there is any, I dont know.

EDIT: Rethinking it, you might be able to rig it up so that one stick handles one command, and switched to the other, like dual channel maybe? That would be kinda nifty.

bigfoot · Apr 14, 2004

i think he is saying he wants to know why you cant run a athlon xp at 400mhz x2=800ddr to = the 200mhz x 2 ddr dual channal with would be like having pc800 ram 6.4gbs so then it would be like if the cpu was sync with the ram because the cpu isnt dual channal so lets call it 400x2 and 200x4 man i suck at explaining stuff like this i get funny looks from ppl i try explaining stuff to...lol but yea i tryed

LOL, u got it! yea, i'm having a hard time explaning it too obviously.

theguywiththeha · Apr 14, 2004

lol...cool so i do know what you were saying seems like no ones else does

Captain Newbie · Apr 14, 2004

bigfoot said:
I understand almost exactly DDR works, but what I mean is 400Mhz LITERALLY, u can call it DDR800 if you wana.

OH!

Well, historically, AMD processors have benefitted from low latency RAM--DDR1 style. A recent article by xbit labs (i think) read that AMD may adapt the uncertified PC3500/3700/4000 standards for DDR1 because DDR2 is 1) new, 2) untried, 3) high latency but good clock rate.

We may see Athlon64 memory busses running at 250MHz x 2 x x (DDR500 x 2 channels) because AMD is hesitant to move to DDR-2 right away...or so says Xbit (IIRC, this is mostly from memory

)

Power on.

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