OCZ doesn't indicate on their site whether these are single or dual sided modules ... so you'll need to ask your vendor (who may/may not know without looking at the modules). If you're buying locally, just look at the modules before you buy them. You simply need to know if there are 8 memory chips or 16 memory chips on the module (i.e. are there memory chips on both sides?).
They'll still work if they're double-sided, but the BIOS will slow down the memory clock to help compensate for the degraded signal caused by the high bus loading. I never install 4 double-sided modules on a system -- you'll have a far more reliable memory subsystem if you follow that advice :-)
