i currently have a Kingston HyperX 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model KHX8500AD2K2/4GR
Cas Latency 7
these are discontinued however i would like to upgrade to 8gb ram and buy another 4gb kit but all the avliable modules are now
can \ will mixing both kits work on the same board
ASUS M3N72-D AM2+/AM2 NVIDIA nForce 750a
Hard to say. Usually memory will just default to the slowest module. That is a huge difference though.2.0 vs 2.3v and cas 7 vs cas 5 makes it a crapshoot. Too bad DDR2 is so expensive now or I would say just get an 8GB kit.
I would not try to match the 2 but it may work if you try it, thus saving you some money. I hate to give wrong info but I really just do not think those will match well with such different voltages and cas latency. My opinion is don't try it.