thats amazing thank you for all the information truly !!
now i have been on the phone trying to order the parts for the computer and so far its looking good im going to try the new cards 7750s and see how it works or where i can max it out at and then go from there
but the other thing is does the CPU need to be good or i can do a dual core 3.2 processor AMD ??
and the power supply ofc is about 550w and ram is 2gs and harddrive is about 500gs motherboard is gonna cost me around 70 - 80 $$ its a gigabyte 1155 chipset
but the most important part is the GPUs , the other thing i dont understand is how would i be able to run 2 different applications (CGminer) on 2 different cards or it doesnt work ? like this is the part that im confused !???!
and what do you suggestion i start mining LTC OR FTC ??
I'm sorry, I'm laughing at the power supply, partly out of personal experience. Back in early July, I ran the numbers, figured my spare 550w PSU would be enough to run a 7950 plus the rest of the system components. I ended up "releasing the magic smoke" from the PSU. Toast.
I think you REALLY need to go look at Bitcoin Hardware comparison and Litecoin Hardware comparison, and run your own numbers. In general, I wouldn't even blindly suggest someone start mining unless they had a 650w minimum PSU... and at that, only one card on that weak of a PSU. Just blindly guessing for 7750s, I'm going to blind guess they need 200w each... then you also figure the core components of the system take 100-115, and you always want an additional 10-20 pct of your power supply's power to be spare, just in case something pulls a ton of extra power.
Your RAM is EXTREMELY low for ANY purpose. Sure, its moderately adequate for a desktop computer that will run office applications and browse websites. Whoever is selling that to you is selling you the bare minimum for running Windows... I can't fault them, because you probably didn't tell them your needs. You are essentially doing high-end intensity gaming, or high end video editing and 3D rendering. THAT is what they should be developing the system around, RAM wise. 8GB RAM. Someone told me have as much RAM on your motherboard as your cards have... others tell me 8GB is enough.
You need a current gen or gen-1 processor. You DO NOT need a top end processor, mining is not as processor intensive as you might think... unless you're mining scrypt-jane CPU-only coins. I don't know AMD, but I'll tell you the equivalent from the Intel side. The newest generation that came out in July is Haswell (Core i5 and Core i7 4xxx numbers. People were mining before July. You don't need Haswell. Before July, processors existed in the following order, from weakest to strongest: Celeron, i3, i5, i7. You don't need an i7 to mine, its overkill... I use my i7 for server farm stuff and teaching myself vmWare ESX virtualization, and running about 10 virtual servers... like I said, overkill. You can mine on the weakest of that generation, a Celeron, which is what the Tacotime crate build said that I recommended you to go look at.
Again, I think you REALLY need to go look the Tacotime crate build at
https://bitcointalksearch.org/topic/litecoin-build-for-noobs-3x-7950s-18-mhs-in-a-10-crate-case-163306 for suggestions on hardware. I don't think you did.
Cgminer, to your question, runs however many cards you let it. Don't crossfire them. If you leave defaults, it picks up all the cards. If you provide specific arguments, it runs specific cards. If you tell it to run one card in desktop mode at a low load and the other card at a high load, it'll do that. You CAN tell it to mine on card 2 while you run Skyrim on card 1... but you'll notice both will take a hit in total performance.
As to what coin to mine: Again, I suggest you go look at coinchoose ... and look at it a few different times during the day, over a few days. There are times certain coins are higher than others, and then there are times a coin will surge to the top, then after a little while drop way down to the bottom. I can't tell you a certain coin to mine... neither can many others. Those who DO tell you a coin, are either A) Shilling that specific coin; B) repeating what someone else told them; or C) giving you advice that is only good for a couple weeks.
This hobby (and that's how you should treat it, as a hobby) changes WAY too fast to give you advice on any one coin. I think with some of these questions you are asking, maybe you should just use the card you have in the computer in front of you, download CGminer and cgwatcher, point at a pool like multipool.us, and browse the posts on the first couple pages of each section of this forum and the forums on litecoin org.
DO NOT expect to get a 100 percent ROI in your first 90 days. That's one of the bigger fallacies out there, especially for a newbie who farms at anything less than fully optimized and tested settings, 24/7. That fallacy also doesn't take into account your support hardware, it assumes you already have a motherboard/ram/cpu/hdd. Treat this as a hobby, that whatever money you put in, you probably won't get out... and just be happy when you get that extra little gift back.
And again, go look at the tacotime crate build for hardware suggestions. He's one of the higher-tier people on the hardware side of the forum.