Dual channel DDR mode is surprisingly demanding. Just using more than one memory module is well known to pull down the ceiling RAM bus speed you can achieve, in many cases, but dual channel is much worse. A lot of RAM that's fine running at full processor bus speed - 250MHz before doubling, say, for a decently overclocked P4 system - when it's the only module in the system, will probably need to be wound down to 2/3rds of the bus speed to work in dual channel mode. That'll put it well below its rated speed, if it's fancy PC-something-above-3000 memory. But anything faster just won't work. You may be able to load your OS, but good luck running applications. Kanske,, inte.. ^^