A Big Ram Quandry
As competition in the video card market increases, so too do attempts by AMD and Nvidia, as well as their many vendors, to make their cards appear special and different in a crowded market. There are many ways to do this. Free games, factory overclocked GPUs, and modified coolers are all popular methods of making products stand out from the crowd. The most common method, however, is the creation of a card that includes more RAM than the card would normally ship with. It is virtually a guarantee that any video card released will be followed up in a few months by a version of the same card with added video RAM.
Advertisers and marketing professionals love being able to sell cards with more RAM included, because RAM can be easily quantified with the statement that more is better. RAM is also a fairly common term, and most people already have an understanding of the correlation of RAM with performance from their experiences using desktop or laptop PCs. Telling a customer that they’re buying a product with more "stream processors" may result in some head-scratching, but anyone who is looking to buy their own video card probably has an understanding of RAM. But is more really better? Or do video cards with added RAM simply exist to increase the profit margins on existing hardware?
Understanding RAM in Video Cards
The first step in understanding the value of cards with added RAM is understanding RAM itself. If you’re familiar with PC hardware, then you likely have a basic understanding that RAM on a PC acts as short-term memory. The PC stores information it immediately needs in the RAM so it can access the information quickly. Having more RAM can make programs more responsive, and having far too little RAM can make programs impossible to run at all. The responsibility of video RAM is similar, but simpler, as the primary task of video RAM is simply to store the data needed to drive a display device. It is essentially a middle-man, collecting the data from the GPU before sending it on to the display device. Video RAM is also different from the RAM normally in your PC in that it is designed to have an extremely high bandwidth. Each frame that your video card renders is an image of its own, and in order to be smooth the video card needs to be rendering around thirty frames per second. That is a lot of information that must be moved very quickly.
There is some variation in the different kinds of RAM seen in video cards, although that variation is only an occasional occurrence. Currently, most Nvidia and lower-end ATI Cards use the GDDR3 standard. Higher-end ATI cards, like the Radeon 4870, use the faster GDDR5 standard. GDDR5 memory has an advantage over GDDR3 because it provides more bandwidth, which means that more data can be sent between the video card to the display device at once.
Translating To Performance
One thing to remember when talking about RAM is that while many critics and advertisers use the terms "faster" and "slower" to describe video RAM, the video RAM itself does not do any processing. It is in no way responsible for actually creating the images that are sent to your display device. Despite what marketing blurbs often claim, those video cards which feature more RAM often have exactly the same level of performance as those video cards which feature less RAM. This is because while the card with more RAM has more space in which to put data headed to the display device, there is no need for that extra space. Think of it as you might think of DDR2 RAM in a desktop PC. If you’re running a program that requires 512MB, that program will run the same on a PC with 2GB of RAM as it would on a PC with 4GB of RAM.
So what’s the point of more video RAM? Well, to continue the analogy with DDR2, imagine trying to run that same program with a minimum requirement of 512MB of RAM, on a PC with only 256MB of RAM. Chances are it would run very poorly, if at all. The same is true if the game you’re trying to play on your video card requires more RAM than your video card can provide. RAM does not scale. Either your RAM has the capacity and bandwidth need, or it doesn’t.
This means that buying a card with more video RAM is only a good idea if you feel that you’re going to be asking a great deal from the card. As you kick up the resolution and the graphics detail, each individual frame the card is rendering becomes more complex and requires more memory. Buying a card with more video RAM is not a question of increasing your frames per second. It is an absolute wall. There are very few games today that are intense enough to challenge even 512MB of video RAM, but those games which do will simply force your video card to give up and go home. You will know the wall when you come to it because the framerate will suddenly plummet into the low teens or even the single digits, making the game nearly impossible to play.
How Much RAM Do I Need?
There are two things you should consider when looking at video cards with different amounts of RAM. The first is the resolution you play games at, and the second is the video card you’re looking to buy.
For current games, 512MB of RAM is more than enough in nearly all situations. Only gamers looking to play on a 30" monitor should worry about more, although those playing on 24" monitors should be aware that their cards may run into limitations due to RAM in a year or two. If you’re playing on a monitor smaller than a 22", 256MB will be perfectly suitable for your needs.
However, no matter what the native resolution of the monitor you’re playing games on, you should also seek to balance the amount of RAM that is on your card with the performance of the card. As mentioned, RAM does not increase the speed with which the card can render frames. This means that you should avoid a card with low-performance GPUs paired with heaps of RAM. For example, it is possible to buy a Geforce 9500GT with 1GB of GDDR2 RAM, despite the fact that the Geforce 9500GT’s GPU is not fast enough to even produce a frame-rate high enough to require that much memory.
Video Card RAM is a balancing act, but when in doubt, you’re typically better off buying a card with less RAM than one with more. By and large, the promotion of video card RAM is driven by marketing, not by actual performance. The only exceptions are those cards which are actually powerful enough to drive very large displays, like the Radeon 4870 or the Geforce GTX260 – and even in those instances, the versions with additional memory are only worthwhile if you’re pairing them with an extremely large display.