we should say what determines what...
to help out, we really should be saying what determines what.
for example, once you decide on a specific type of video card (for example here PCI-E), then you HAVE to get a motherboard that is for pci-e video card, and avoid a motherboard that is built for avg video card, cuz they simply won't go together.
another 'match' that is necessary is matching chip to motherboard. if you get an amd chip, you must get a motherboard designed for that specific amd chip socket type. if you get excited about some intel chip, then you have to get a motherboard that has the correct intel chip socket. chip must match motherboard.
also, ram must match motherboard.
so, the motherboard is key to the rest of the components.
usually, the good motherboard companies make similar mb for both amd and intel, so you really can just focus on what chip you want, then let that guide you to whatever asus or gigabyte or whatever brand motherboard. then, just get decent ram that matches.
most motherboards nowadays will 'match' with both ata and sata hard drives, so that is not a problem.
if this will be your first computer to build, you probably don't want to 'raid' hard drives, so you don't have to worry about what styles of 'raid' are supported by the motherboard.
so, i would read up on chips, and decide intel or amd. (tomshardware and other sites have reviews by enthusiasts.) then move on to pick a motherboard that matches the chip.
the case must fit the motherboard: the case must be the right size, and have screw holes in the right places. There are several 'formats,' but mainly for home pc people are using either 'atx' or 'micro atx' AKA 'matx' or 'm-atx.' atx is 'normal.' m-atx is for a smaller-size computer, more basic, with less options and features, and often but not always specifically designed to have a lower price.
as you shop for motherboards, and look at format, the low price mbs will be 'm-atx.'
this is what they give most of us at work so they can give many people decent computers for not much money - cuz I am not supposed to be playing vid games or tricking out my work computer.
i think it is just basically better to go for the atx so you have options in the future, like you mention, for upgrades.
most motherboards nowadays have pci-e vid card format, and there are many video cards for pci-e running from $30 (i don't play games so I just get a well-reviewed $30 or $40 vid card) up to $600 or more.
and, read up on ram that fits the motherboard. you can go cheap, but it is often worthwhile to go ahead and go the extra $50 for decent ram. or at least wait for a rebate deal on good ram versus no-name or budget. --also, you may prefer to get the newest, fastest, still-pricey ram, ddr3, but many people are still buildign great systems with ddr2. so, if you want to pay a little more to get the newer, faster ram, that will dictate/limit the motherboard: a motherboard must host ddr3 i norder to fit that ram, if that's what you want. for the money, i would rather build a decent system with ddr2, knowing that in 3 years i will get the itch to build again, and will get ddr3 or whatever is newer at that point.
then, hard drive must match. like i said: most mbs can run both ata and sata. satas are faster and no longer cost more, so it is a no-brainer nowadays. there are other types of hard drives. so make sure you are getting sata or ata [aka, ide] and not scsi or some laptop drive, ssd drive, etc., unless you really look into it. sata will be easiest plus best deal for the money.
cd/dvd drive just needs to be ide, and probably will be, and most mb you will be looking at will be ide. floppy if you actually bother to get one will be ide. no big decisions there.
now, with all of those decisions, you can figure out how much power your computer will require when running at full tilt, like when watching videos plus burning a cd plus maybe another program or two open.
an 80 watt light bulb needs 80 watts. a 1400 watt hair dryer requires 1400 watts.
computers vary a great deal in required wattage.
the video card will be the main thing dictating if you need a lot of power or not. the chip can also dictate this a lot: some chips you will notice say they are '145 watt,' while some say they are '45watt'. the more watts, the more power it needs to run at full tilt. so you can actually shop and decide chip based partly on the power it will require. then, knowing wattages, you can list all of your potential components, and hunt around the web for some data on the power they require. tomshardware is good for this, and so is silentpcreview and other sites.
so, you total the potential wattage needed at peak / at max. then, pick power supply that is sufficient. if this totals up to 300 watts, then get a 400 watt power supply (power supply also called 'psu' power supply unit).
if it totals up to 220 watts, get a 300 watt psu.
i prefer to figure out the lowest safe wattage level, so i can devote money to quality instead of higher watt ratings.
everyone likes to get some super big power supply, as if it is gonna do anything to make the comp run better, but it won't.
a 80 watt light bulb needs 80 watts. a 1400 watt hair dryer needs 1400 watts.
if your comp needs 220 watts, don't get talked into a 500 watt power supply.
psu vary in quality greatly. don't go cheap. at worst, it will fry a component or the whole system if you get one that was not made well. but even if it doesn't just fry everything, inconsistent power means you will have all kinds of weird problems, and you will get a dozen opinions about what it is - cuz the ram will mess up, the 'chipset' will mess up, etc., since they are getting inconsistent power - it is like lights flickering when a major appliance comes on in your house. nowadays, generally, the decent power supplies will be those certified "80" efficiency rating. look for that and you will generally be ok, although i had a great antec die on me, and everyone has a horror story about a good brand psu dying on them.
now, the power supply needs to match your motherboard: like power supply 'ps' needs to be 'm-atx' or 'atx' depending on the mb.
the case needs to fit the style of mb --and this lets you know that the mb will fit in it plus lets you know the correct power supply will fit, although it may not fit easily
.
so, how to build / what do you need to know: these are my thoughts on how to match things up.
case: match to 'form factor' of motherboard atx or m-atx. i am not 'big' on case selection myself. others are. a decent case can help keep system cool, and can minimize the noise. also, they can leave room for expansion, or can look cool. i am over 30yo so i no longer care about the cool looks.
this is how i think abt building.
others may have additional or differing comments. i nfact, i would be intersted in hearing other people's thoughts on what component you start with when planning a new system. -Row1
