My computer's main memory consists of 2 modules of DDR 400 (Kingston). I have two slots free and I want to put more memory. I remembered from the SIMM epoch that if you wanted to upgrade your memory you should buy memory with the same response time. Did this or others limitations exist in order to upgrade my memory?.
My computer is:Athlon 64 3000+ (socket 939 Winchester) ,2x512 DDR400,Gigabyte nf4,X800XL 256,120GB.
Is any possibility that memories DDR400 will not exist in the future?

My computer is:Athlon 64 3000+ (socket 939 Winchester) ,2x512 DDR400,Gigabyte nf4,X800XL 256,120GB.
Is any possibility that memories DDR400 will not exist in the future?
