Archived from groups: alt.comp.hardware.pc-homebuilt (
More info?)
"esara" <esara123@hotmail.com> wrote in message
news:fd7d27e7.0404150759.28d49a3d@posting.google.com...
> Jim you said
> <quote>... In this case, you'd have the CPU FSB running asynchronously
> to the memory (166MHz vs. 200MHz).</quote>
>
> But I thought AMD XP2600 has FSB = 333Mhz. So in this case even with
> PC3200 he can get good synchronization! Am I right??
This is where the confusion comes in. We have to differentiate between the
actual "clock" speed, vs. *effective* speed (for lack of a better term).
When you install that AMD XP2600 w/ FSB 333 in your mobo, the motherboard
will generate a 166MHz "clock" to drive the FSB. That AMD CPU supports an
actual clock of 166MHz (spec'd, assuming no OC'ing), but because it
implements DDR, it's doing twice (2x) the amount of work as a non-DDR
processor w/ the same 166MHz clock. It does this by sending data on BOTH
the up and down side of the clock cycle. IOW, it's more efficient. AMD
sells and markets the CPU as 333MHz FSB (2 x 166MHz clock) to make clear
this is the peformance level you can expect, but it's not the actual "clock"
speed that it runs at.
Same holds true for PC3200. This memory "clocks" at 200MHz (spec'd,
assuming no OC'ing). The PC3200 label is simply a reflection of its
performance, which is 200MHz (clock) * 2 (for DDR) * 8 (bits wide) = 3200!
IOW, the speed of the memory is 3.2Gb/sec (theoretically).
Finally, for synchronization purposes, it's the clock that matters. Since
that AMD is 166MHz clock, and the PC3200 memory is 200MHz clock, these are
NOT synnchronized. Using that AMD processor (w/ 166MHz clock), the *ideal*,
synchronized memory would be PC2700 (2700 / 2 (for DDR) / 8 (bit wide) =
166MHz clock).
Of course, some people try to *force* synchronization by OC'ing one or the
other, but that's another story for another time.
HTH
Jim
>
> "Jim" <null@null.com> wrote in message
news:<r4dfc.2650$Yf6.587@fed1read07>...
> > You're on the right track, but there is a more precise, accurate way to
> > describe it. To keep it simple, let's assume no overclocking.
> >
> > You typically configure the CPU (FSB) on the motherboard to match the
clock
> > speed of the processor. Assuming this Barton is 333MHz DDR (166MHz
actual,
> > or "clock"), that's what you use. Usually you buy *matching* memory so
you
> > can run synchronously (1:1), which simply means it has the same "clock"
> > speed as the CPU FSB. PC2700 is 166MHz actual/clock (333MHz DDR), so it
is
> > a perfect match in this case.
> >
> > So in the end, you arrived at the same/right conclusion, but I didn't
want
> > to leave a misimpression. You don't typically buy memory at some given
> > speed "X", then set your CPU FSB to match it. That's literally how you
> > described it. You never let the memory speed *drive* the CPU FSB, it's
the
> > other way around. You buy the best CPU you can afford, they buy memory
to
> > match it. The cart pulls the horse, not the other way around!
> >
> > In the simplest case, you match CPU FSB "clock" speed to memory "clock"
> > speed. But nothing prevents you from running FASTER memory if you
prefer,
> > just so long as your motherboard supports it. So it may also be
possible to
> > run say, PC3200 (which is 200MHz "clock"). In this case, you'd have the
CPU
> > FSB running asynchronously to the memory (166MHz vs. 200MHz). It would
> > require the motherboard to support a 5:6 CPU/DRAM ratio too (166 / 5 * 6
=
> > 200), at least to run at spec. This isn't always more efficient,
> > asynchronous behavior sometimes undermines any benefits you expected by
> > increasing the memory speed, in this example, by 33MHz. But some people
do
> > anyway, and claim more performance.
> >
> > Some people also buy faster clocked memory because they intend to
overclock
> > the CPU FSB (run above it's spec of 166MHz in this example). By doing
so,
> > their attempts to get more clock speed out of the FSB and continue to
run
> > synchronously (CPU clock = Memory clock) is not hindered by the memory,
the
> > *extra* clock speed afforded by the memory at 200MHz provides *headroom*
for
> > the overclocking attempt on the CPU FSB. IOW, on the march to reach
200MHz
> > w/ the CPU FSB, the memory is never overclocked itself, indeed, it
always
> > remains underclocked.
> >
> > HTH
> >
> > Jim
> >
> >
> > "Jim Caldwell" <Jamesw@grandecom.net> wrote in message
> > news:c5jhol$2g73b$1@ID-153828.news.uni-berlin.de...
> > > I have a Asus A7N8X with a XP 2600 Barton, 1 gb of PC 2700 DDR ram. I
> > think
> > > PC 2700 is equivalent to 166 Mhz., so is whatever your RAM is rated
for
> > what
> > > determines what you set your front-side bus speed to (in this case
166
> > > MHZ)?
> > >
> > >
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