| In article <
[email protected]>, Wilf
|
| > 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.
|
| 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).
|
| 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 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.
|
Um, maybe I missed something here, but there ARE AMD XP CPUs (Barton
core) that run 400 MHz FSB.
Some are listed here:
http://www.newegg.com/app/viewproduct.asp?description=19-103-390&DEPA=0
In fact, this page lists a "refurb" OEM XP3200 for $135, very
tempting, noooo nooooo, hellllllppp, I can't stop myself from clicking
the "add to cart" button.
