Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
Paul wrote:
> In article <tqo1d0padtkbnnhj6h7dvfr46onc9i1f2l@4ax.com>, Wilf
> <wilf@NOSPAMmondenet.com> wrote:
>
>> The Asus A7N8X has a max of 400FSB and the AMD CPU has aMAX of 333 FSB
>> how do you use the 400 FSB. Can the CPU run at 333 FSB and the ram at
>> 400 MHz. I find it puzzling can anyone explain this.
>> Thanks
>
> You crank the FSB from 333 to 400 (i.e. 166MHz to 200MHz clock - the
> FSB is double pumped). The processor runs 20% faster than
> normal. Then, you can run your memory at DDR400 as well, and they run
> in sync.
As already posted, there are two XP CPUs, Bartons, that have a 200MHz DDR
FSB.
> With older AthlonXP, the multiplier was unlocked by the A7N8X, and
> you could crank up the FSB, crank down the multiplier, resulting
> in a more or less constant core frequency, but with the benefit of
> getting the FSB and memory to run at DDR400. Fortunately, with the
> currently "super-locked" AthlonXP being shipped by AMD, a 2500+
> can handle the overclock from 333 to 400, without needing to reduce
> the multiplier.
>
> Barton 2500+/FSB333/512KB cache has core frequency 1833MHz. It runs
> 166*11. On the A7N8X, you crank it to 200*11, as the 11 multiplier
> cannot be changed on the current shipping processors. Look up
> "Barton 2500+" in the AMD section of
http://www.cpudatabase.com
> and only 89 of 614 processors tested couldn't make that overclock.
> With the processor at 200*11 and the memory at "100%' or "sync",
> the memory ends up at DDR400 (200*2).
The Mobiles are unlocked, so you can still crank the FSB up and the
multiplier down.
> A little background -
>
> The AthlonXP has a 64bit data bus. Two 64 bit words are transferred
> per FSB clock cycle (double pumped). A DDR DIMM is 64 bits wide. Two
> 64 bit words are transferred per memory clock cycle. The "bandwidth
> balance" occurs when the CPU clock equals the MEM clock, using only
> a single DIMM. On an A7N8X family board that runs in dual channel
> mode, the memory is actually able to deliver data twice as fast as
> is needed - that is why dual channel doesn't help by more than 5%
> on those boards. That is also why the A7N8X-X is an acceptable
> board, even though it is single channel only.
The gains are most apparent when you use a lot of PCI devices. Since pretty
much all PCI devices can bus master (DMA) they can communicate directly with
the memory controller for reads and writes. This means that if the CPU is
throttling one channel, the other channel can serve the PCI devices. (It's
obviously not as simple as that, the transfers would be interleaved). This
is why the built in graphics ones see a benefit. AGP can bus master, hard
drives, USB, sound... so the more "other" stuff you do, the more gains
you'll see.
> The P4 Pentium is 64 bits wide and transfers four 64 bit words per
> per FSB clock cycle (quad pumped). The two DIMMs of a dual channel
> P4 board each deliver two words of data per memory clock, so on
> a P4, balance is reached when running dual channel with FSB:MEM
> at 1:1, and that is why dual channel is so desirable on a P4 board.
> On an AthlonXP board, dual channel is "nice to have", but except for
> the A7N8X-VM with its built-in graphics core, doesn't benefit the
> user as much.
>
> As I understand it,
I think you understand pretty correctly. I've been reading your posts
tonight and they make excellent reading. They're detailed and above all
correct, a pleasure to read!
Ben
--
A7N8X FAQ: www.ben.pope.name/a7n8x_faq.html
Questions by email will likely be ignored, please use the newsgroups.
I'm not just a number. To many, I'm known as a String...
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