DDR Ram isn´t as new a technology as you may think, Graphics cards have been using these chips for well over a year now - to great success. DDR simply means, "Double Data Rate" - theoretically twice the transfer rate of Normal SDRAM (Only Single Data Rate). There are 2 flavours of DDR Ram, PC-1600, and PC-2100. Both are DDR Versions of the PC-100 and PC-133 Ram, hence PC-1600 = DDR PC-100. All AMD Athlon based CPU´s can use this Ram at PC-1600 spec, but only the very latest 133 Mhz bus Athlon CPU´s can use PC-2100.