Hi, I have an old system, specs- CPU - AMD Phenom II X4 955 3.2GHz Motherboard - Asus M4N78 Pro RAM - Corsair XMS2 4GB (2 x 2GB) DDR2 800MHz (Link - http://www.newegg.com/Product/Product.aspx?Item=N82E16820145184&cm_re=corsair_ddr2_4_gb-_-20-145-184-_-Product) GPU - XFX GTX 260 Core 216 HDD - Seagate 500GB 7200RPM PSU - Seasonic X-650 Gold I bought another 4GB of RAM from G.Skill, Link - http://www.newegg.com/Product/Product.aspx?Item=N82E16820231209&cm_re=g_skill_pi_black_ddr2_4_gb-_-20-231-209-_-Product Now, here's the problem. I didn't realize mixing RAM would cause so much hassle. Corsair has a rated voltage of 1.8V and the G.Skill is rated for 1.9V. G. Skill doesn't work under 1.9V, therefore I have kept them both at 1.9V. I would like to know- 1. If overvolting is fine for the RAM, although not much I just want to confirm. 2. I have tried the pairs in all mixed slot configurations and compatibility issues still exist - like for instance sometimes it won't even post. When it does, it works fine, even under gaming. Currently, I have manually set the timings and voltage in BIOS. I would like know if there's anything more I need to know while mixing RAM. Cheers!