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

A friend once asked me, "What should I get? A 128-bit graphics card, which is cheap? Or a 256-bit graphics card which is a bit expensive? Can you tell me 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.