If I was to get a m'board capable of running DDR memory in dual mode what
would general perfomance difference be between running:
2 X 512 PC2700
2 X 512 PC3200
Considering only "PC2700" vs "PC3200", there is no performance
difference, the motherboar determines the speed. That is, unless
your CPU uses DDR400 FSB, then you want the PC3200. PC3200 is a
better buy today regardless as there is more margin of
stability... choose CAS 2.5 parts over CAS 3.
or in non-dual mode
1 X 512 PC3200
Dual mode is more useful on Intel CPUs, and most useful with
integrated video (on either AMD or Intel platform). Considering
these limitations, if there is a chance you will later upgrade
the memory further, buy the single 512MB module instead of the
two smaller.
Or is it all hype and the performance difference between the above is very
little?
You did not mention the rest of the system. It could be very
little or could be significant. Even with an integrated video
motherboard, the difference is most significant only in demanding
use like 3D games (older games, newer games won't run very well
on integrated video no matter what the memory configuration).
Having written that, there is still some tweaking that can help,
it's even possible to run Doom 3 on integrated nForce 2 video,
but it looks like crap due to all the quality compromises that
have to be made.
If I went for the 2 X 512 PC2700 route (since I already have an unbranded
[maybe samsung] 512 PC 2700 stick) would it happily run with another brand
(or equally unbranded) 512 PC2700 stick?
What is "it"?
In general, adding a 2nd module should be fine, providing you
only need 166MHz, DDR333 memory bus support, and the motherboard
is properly designed, stable with two different modules (which
may have different timings). BIOS updates often help to resolve
memory mismatch problems, but there is no guarantee that your
(unknown) board is stable before or after, you'll just have to
assume so and return the module if it's not stable. Odds of
success are better by avoiding generic or binned budget-grade
memory.