128-bit Versus 256-bit PC Video Card Memory Interface

All of us may think when going to buy a graphic card ,What should I get? A 128-bit graphics card, which is cheap? Or a 256-bit graphics card which is a bit expensive? What is the difference?" Well, the 256-bit graphics card is usually more expensive for a reason. That is the "bus". Today, the most common graphics cards run at a 128 or 256 bit memory interface. But we are now (at the time of writing) seeing pretty high numbers such as 512-bit memory interface from high-end cards especially those that have 2 graphics cores.

First, you need to understand what a "bus" means. It is simply the path where data passes through. So in this case, the memory interface has a 128-bit sized path or a 256-bit sized path. Let's translate it into a more understandable concept. Let's compare 2 highways. Highway 128 has 4 lanes and Highway 256 has 8 lanes (I just thought of these so if there's any similarities to real highways, well, it's just coincidence). Theoretically, more cars can pass through Highway 256 right? So if there are 400 cars, it will take less time for them to pass through Highway 256 than Highway 128 since they can spread out to 8 lanes instead of just 4.

So, now that you have the concept, let's go back to pc video cards. As you can see, more graphics data can pass through the 256-bit interface compared to the 128-bit interface. If there is just very few data, you probably won't see much of a difference (if the graphics core and memory clock speeds are the same that is and pretty much everything else). But when there are lots and lots of data (this is usually when you're running a 3D game with ultra high quality visual settings with maximum anti-aliasing and anisotropic filtering), more data can pass through the 256-bit interface which could result in a much higher frame rate per second.

Aside from the questions above, there is one question that I think needs to be answered as well. Is it always good to buy 256-bit memory interface pc video cards than 128-bit memory interface cards? It is recommended to buy 256-bit cards over 128-bit but just to be sure, do a little research as there are very few cases where it's also ok to get a 128-bit card.

Here's why. An Nvidia 9600GT 256MB 128-bit card is better than an Nvidia 9600GSO 256MB 256-bit card. Let's say (just an example as it may differ from one brand to another) the 9600GT has a 650 mhz core clock (speed of the graphics processor) and 1800 mhz memory clock (speed of the video memory) and the 9600GSO has a 550 mhz core clock and 1600 mhz memory clock. This means that the 9600GT is faster.

Let's translate it again to highways. This simply means that the speed limit on a 9600GT highway is much higher than the speed limit of the 9600GSO. So, if there are 20 cars on each highway, cars can travel much faster on the 9600GT highway. Data transfers are faster on the 9600GT resulting in higher frame rates unless there are lots of data (in which case the 256-bit could out perform the other).

Well, I do understand that it is tough to choose between two video cards especially when you consider the memory interface bit rate. There are other considerations as well such as core and memory clock speeds, features, brand, etc. But again, what you can do is to research and get feedback from users. Compare them and base it on your needs. Oh and also, this holds true to all memory interfaces. Hence, a 320-bit card will take on better graphics data loads compared to a 128-bit card. Hope this helps.

credits to : Aaron Tadeo