i was going to make a home theater PC to hook up to my 50 inch living room TV. i wanted to make it as cheap as possible because i was just going to use it for you tube, hulu and netflix. but then i found HP dc7800 i am going to put the cheapest video card i can find that has HDMI and hook it right to the TV. the HP dc7800 has 2GB DDR2 ram. i was wondering if i had to buy DDR 2 ram or can i get DDR3 ram. and if i can use DDR3 ram do i have to remove the DDR2 and only have DDR3 or can i mix it. and any suggestions on the best brand or types or best deals will be taken in to consideration i have no idea whats a good brand or price for ram. thank you for all ur help and support for this and every other tec query i posted in the past.
unfortunately, DDR2 and DDR3 are completely incompatible. While they have the same number of pins, the notch, therefore the layout, is completely different. You will have to buy DDR2 ram or upgrade to a DDR3 motherboard(and possible get a new processor)
You cannot mix both the rams as others have already said.
You cannot add DDR3 memory in your computer as it is not supported.
For best DDR2 memory but the corsair dominator gt cards, they are the best but also don't come cheap. Try to find if someone is selling them cheap.
According to me the quality chart goes like this
Corsair, patriot/g skill, mushkin enhanced, can't say anything about Kingston because I've heard a lot of people praising and complaining about it and since I never used myself can't say anything about it.
OCZ also made some nice ram cards.
There are very very few motherboards that can run both ddr2 and ddr3 like Xttony said here is another http://www.outletpc.com/ox6943-asrock-n68c-gs-fx-am3-ma... but most 99% only work with one or the other. Even on boards that had slots for both ddr2 and ddr3 you could only use one type at a time in intel boards and it depended on what cpu you had for AMD boards. In your case you HAVE TO GET ddr2 or it will not work... Go to newegg.com they have good prices for ddr2. good luck