Help me pick a processor for the A7N8X (and clear up some questions for me)!

[StealthX32]

Alrighty. I currently have an AMD Athlon T-Bird 800, and I haven't really spent much time lookin' into computers since the Celery 300A craze. So I'm kinda outta the loop. A couple questions before we start. Back in the good ole days, 4.5x100 meant 100 MHz FSB, which translated into a 100 MHz memory bus. Now, back to today. According to this picture (AMD System Architecture - stolen off HardOCP), the memory bus and the FSB run completely separately at separate speeds, right? So this means, I don't have to have a 200 MHz FSB to run DDR400 at full speed, right? Now, I see some people running their processors at 200 MHz FSB...such as TonyB. What would the advantage be running a 200 MHz FSB? I'm assuming you'd unlock the multiplier and drop it down to allow the significantly higher FSB, but since you don't need to match FSB and memory bus speed, why is this necessary?

So, now, assuming I've got the AMD architecture correctly, and that I want to spring for an Asus A7N8X, and want to get Corsair XMS PC3200 memory...would I be better off with a 2200+ T-Bred A or pay up an extra 20 bux for a 2400+ T-Bred B? Or a 2200+ T-Bred B? I'm assuming I can get the XMS PC3200 to run at 400 MHz (since Anandtech says its possible 🙂 ). And reading a couple articles off Overclockers.com, I came across one article that tells me how to tell processors apart from others, and another helpful article is one from Anandtech that illustrates the differences between the A and B cores. From what I gather, the T-Bred would be easier to overclock, but other than that, there shouldn't be a difference.

So, my primary concerns are probably not overclocking but rather system stability. From what I hear from the nForce2 reviews, a T-Bred B's multiplier would be unlocked without any additional modifications. Which would be nice, since I'd be able to tinker with the FSB without any additional work...and assuming I'll get performance gains from it. So, what do you all think? I was gonna get this all from Newegg.com since shipping would be free, and they have everything in stock, but they only have the 2200+ in a T-Bred A core (according to that article from Overclockers.com). So 2400+? Grah. Straighten me out please. Thanks all!

 

[Magnumike7]

From what I have read the 2400+ is the "sweet spot" for the B core cpus. if its only $20 bucks I would go witht he 2400.

 

[The Sauce]

the memory bus and the FSB run completely separately at separate speeds, right? So this means, I don't have to have a 200 MHz FSB to run DDR400 at full speed, right?

Right, but you would be foolish not to. You get the best performance when you "sync" the memory with the fsb. There is a rather severe performance penalty for running out of sync, and you'd be much better off running them in sync at a slower speed.

What would the advantage be running a 200 MHz FSB?

If you buy some PC3200 and sync the FSB/memory at 200 MHz, then you get crazy-phat memory bandwidth. That is the advantage. As I mentioned, if you run out of sync it is not nearly as good. You would probably be better off running 166/166 than 166/200 (FSB/memory).

I want to spring for an Asus A7N8X, and want to get Corsair XMS PC3200 memory

Good choice.

would I be better off with a 2200+ T-Bred A or pay up an extra 20 bux for a 2400+ T-Bred B?

Whatever you get make sure that it is a 333 MHz compatible unit. There has been some trouble unlocking lower multipliers on these boards so getting a 266 chip and planning on lowering the multiplier to run it at 333 is not a sure thing. There is some socket-mod people out there are doing to unlock the lower multipliers, and/or bridging L3 on the CPU. Or you can do what I did, which was to get an 1800+ and overclock it to 2400+. Then the issue is moot.

what I hear from the nForce2 reviews, a T-Bred B's multiplier would be unlocked without any additional modifications.

Not sure about that. As I mentioned on the A7N8X i think there has been trouble with the lower multipliers which, of course, are the ones you would need if overclocking the FSB.

 

[The Sauce]

Thinking it over...

Between those two procs I would definitely pick the 2400+...as long as it's a T-Bred "B" and its rated at 333. The upper limit for the "A"s seems to be around 2400 so you won't get much of an overclock there...and if you are planning on overclocking the FSB and can't lower the multiplier, then this cpu won't leave you much room to play. The "B" should be able to clock higher so even if you can't get the lower multipliers, you should be able to go higher with this chip. Either way, rumor has it that ASUS's next BIOS update will obviate this issue by giving you the lower multipliers. Cheers.

 

[StealthX32]

Well, the only TBred Bs rated at 333 MHz FSBs are the $300 ones. 😛 Those being the 2600+ and the 2700+...which is about twice the price of the 2400+. 🙁 That's why I was all happy to see someone do a lower multiplier with a 266 MHz chip and bump it up to the 200 MHz FSB was for this purpose....but if it's not readily reproduceable, then maybe I'm better off not doing that. Thanks for answering my questions though!

 

[The Sauce]

Well, like I said, you could always gamble $58 and buy an 1800+. Mine made it to 2.0 GHZ (2400+) easily and is presently running 190 x 10. The only reason I am not up to 200 yet is because I am taking it slow and testing extensively after every bump for maximum stability.