I figured as much.....thanks for the response. Maybe I'll sell or trade my
current memory and replace with dual 512MB sticks!!
You can move the 2x256 to slot 1 and slot 2. Place a new 512MB module
in slot 3. (If the chips are the same type, so much the better, as
then the performance of all sticks will scale with voltage the same
way.) As long as the sum of slot1 + slot2 = slot3 capacity, the
board runs in dual channel mode. If the totals are unbalanced, the
board runs in composite mode, where one portion of memory is dual
channel, and the other portion is single channel. For example, stuffing
3x256MB in the board would run it in composite mode. The BIOS would
display "dual channel" during startup, but it is physically impossible
for an unbalanced configuration to be dual channel for the entire
memory.
Unbalanced config gives composite operation -
Will display "Dual Channel" in the BIOS, but one chunk
of memory has no mate.
Slot1 256MB <--- This memory in single channel
Slot2 256MB 256MB Slot3 <--- This memory in dual channel
Balanced config for dual channel -
Slot1 256MB ^ <--- Both channels are stacked to
512MB Slot3 the same height, so can be
Slot2 256MB v accessed dual channel.
Dual channel isn't such a big deal anyway, except when benchmarking.
For normal use, dual channel only makes a few percentage points
difference. (In single channel mode, memtest displays 1010MB/sec
at 12x200 on the processor, and the memory at 3-3-3-8. In an
unstable dual channel config, slot 2 and slot 3, I got 1361MB/sec
at 10x198 on the processor. But, in Windows the difference detected
will be smaller than this.)
As I've just placed an order for some DDR DRAM, I'll be able to test
this stuff out in a few days. My current ram turned out to be bad
(as determined by testing with Prime95), so I'm in the process of
replacing it. I noticed that it was possible to run a higher
stable FSB in single channel mode (the two sticks in slot 1 and
slot 2, with no stick in slot 3). But for benchmarking, the dual
channel config is the one I want to use. At least long enough to
do some application testing.
So, I guess my answer is, you have two options. Buy one 512MB and
use with the current 2x256 sticks. Or buy 2x512MB and sell the
2x256MB. Both configs will be fully dual channel. If the 256MB
sticks are single sided, then there is effectively no difference
between the solutions. If the 256MB sticks are double sided, then
a single 512MB double sided stick will perform better than two
256MB double sided sticks (i.e. for overclocking).
Paul
