3GB RAM in Dual Channel Mode in Vista

[HDTVNZ]

Is it possible to use a configuration of 2x1gb and 2x512mb DDR-800 RAM modules to achieve 3GB RAM in dual channel mode? The motherboard I'm using is an Asus P5B deluxe, and am running Windows Vista Ultimate 32bit edition.

RAM would be configured like this:

Memory slots 1 & 3 - 1GB ram sticks
Memory slots 2 & 4 - 512mb ram sticks

 

[JohnDoe2]

Sorry I can't respond with experience (as I'm currently shopping for a new QX6x00 rig, piece by piece), but I would be interested in knowing which boards COULDN'T handle the 3GB configuration as described, since it seems to make the most sense for 32bit OS users.

 

[HDTVNZ]

The current memory I've got is a G.SKILL 2GB KIT (2x1GB) F2-6400CL4D-2GBPK DDR2-800 (PC-6400) CL4-4-4-12 1.9 2.0V

I can get hold of a this: G.SKILL 1GB KIT (2X512MB) DDR2-800 (PC-6400) CL5-5-5-15 F2-6400PHU2-1GBNR

Are the different timings likely to affect performance? I don't want to overclock anything either. Thanks for any info on this