VRAM and RAM

what are the physical differences between RAM on a graphics card and regular RAM? and is the GPU essentially another processor like the GPU but dedicated solely to processing graphics information?

Why is it so hard to get GB's of VRAM when getting GB's of regular RAM is relatively easy?

 

VRAM is RAM that is solderd into the video card, and is soley dedicated for the GPU to use. Regular RAM, or system RAM is used my the CPU to load things into instead of always acessiing the hard drive, making system performance faster. VRAM does the same thing, but just for the GPU and video related things.

The reason why 1gb+ VRAM cards arnt avalable is because all the VRAM has to fit on the video card, along with the GPU, cooling device, and all the transistors and resistors. There really isnt enough room on a video card for a ton of RAM. And heat is also an issue on new video cards, RAM creats heat to, and could over stress the cooling device and fry the card if you have too much. Plus VRAM isnt the every day 667mhz DDR2 RAM that is used as system RAM. New cards today use GDDR3 I believe, and some top end cards have their ram clocked close to, or over 1GHz. So if they could put 2gb of VRAM on a card, it would so impossibly expensive, it wouldnt be comercially viable, yet.

 

Is the clock speed the only difference between gddr3 and ddr2?

 

Mostly. They're very similar technologies, but GDDR3 is 'tuned' for graphics performance. Cream of the crop type stuff.
Speaking of which, why would you want a 1GB+ video card? Most games don't even push the limits of 256MB currently, and aren't looking to do more in the future. Few cards can address more than that quickly as well.
You also don't use VRAM the same way as you use RAM. VRAM stores only a few things: vertexes, textures and a screen buffer pretty much. Not a whole lot else. Your system RAM is for EVERYTHING (including all of the above at times). So it makes sense to have more system RAM than video ram.
Think of your system RAM as the truck you use for hauling everything, and the VRAM as more something like a sports coupe you use for getting specific things somewhere quickly. Both very useful, but only in their niche. Trying to drive a truck (lots of RAM) like a sports coupe only causes problems

 

Ooh, lots of questions here...

Physical differences? Lots, really. VRAM isn't "real" DDR ram at all (It's commonly labelled GDDR). There are several reason for this. Most of the core specs are the same, but GDDR is usually created before the specifications for the equivalent DDR standard are finalized. (For example, we have had GDDR3 in our graphics cards for years. But the DDR3 standard was only recently finalized, and you still can't buy DDR3 anywhere)
Another difference is that VRAM uses a point to point interface, so the GPU is talking directly to every single RAM chip. Regular system RAM uses a controller to gather data from each RAM chip, and sends it across one common bus to the CPU.

So no, they're not the same, and can't be used interchangably, if that's what you're asking.

It isn't. But consider what 2GB of regular system RAM costs. Would you be willing to add that much to the price of a graphics card? Aren't they expensive enough already?
And next, there just aren't many applications that need more than 256-512MB VRAM yet, so it'd be a waste of money to put several GB on a card. (Actually, I believe you can get workstation cards (NVidia's Quaddro, and ATI's FireGL cards) with 1+ GB VRAM. But they're expensive as hell, and dedicated to different tasks than gaming.
Next, as mentioned, more RAM takes more space, which can be at a premium on a graphics card. Especially when heat output is taken into consideration. The bits that produce lots of heat can't be too close together, and the distance between the GPU and RAM chips must not vary too much, or the timings will mess up. If you look at a graphics card, it'll often have the RAM chips placed in a sort of semicircle around the GPU itself.

Yes and no. Clock speed is really a tricky beast in modern RAM. They claim to double the clock speed every generation, when what actually happens is that they just do more work each cycle.
The difference between DDR2 and DDR3 is that DDR3 fetches twice as much data per cycle. So the clever marketing people decided to brand them as having twice the clock speed.
Same story with DDR2 vs DDR. DDR itself was slightly more justified, because here the improvement was to transfer data twice per cycle. So the effective clock speed could be said to be twice as high as for older SDRAM.
But yes, the "clock speed" is the only *important* difference between DDR2 and 3. There are a few other tweaks made to make these higher clock speeds possible, to lower voltage requirements, to allow higher memory densities and so on.

As for GDDR3 in particular? As I said, it's roughly the same as DDR3, with a different external interface, and with a few slightly different tweaks.

Not sure if this answers your question, but there aren't really any simple answers when it comes to RAM...