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In my desktop I have a basic graphics card, a 1GB ATI Radeon HD 5450. It's served me well through the years, although I am looking at having to replace it as it can't run games as well as it should.

Take Battlefield 2142 and Crysis. Two games released within a year of each other (2006, 2007). It runs the first (maybe not on full graphics) and is playable with decent frame rates (40+). The system requirements for Battlefield 2142 are 1.7Ghz, 512MB RAM and 128MB Graphics which my desktop (Quad Core 2.8Ghz, 4GB RAM, 1GB Graphics) matches fine. This is also enough for Crysis (2.8Ghz CPU, 1.5GB RAM, 256MB graphics). Also other games like Just Cause 2 and Battlefield Bad Company 2 "should" work, but they are so slow and juddery, and I barely scrape 10 fps out of any of them. The intro scenes for both Bad Company 2 and Just Cause 2 play slowly with the audio/video out of sync.

I realize there's a lot I don't know about graphics cards, but I also realize now that it's not just a case of having a 1GB or 2GB graphics card - what are the things that "matter" in a graphics card: the core clock, the memory, the memory clock?

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Why are you sure this is a graphics card issue, not a performance issue from processor/RAM etc? –  Dave Rook Aug 6 '12 at 8:53
    
When wanting to use newest games on highest settings, you get to upgrade your card regularily. –  Thorbjørn Ravn Andersen Aug 6 '12 at 9:17
    
Crysis is known for being a performance hog. –  VBwhatnow Aug 6 '12 at 9:25
    
@DaveRook - I'm not 100% sure, everything else seems to be fine/run well –  tombull89 Aug 6 '12 at 14:29
    
@ThorbjørnRavnAndersen - I don't want to play them on "high" just a decent framerate. –  tombull89 Aug 6 '12 at 14:29
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what are the things that "matter" in a graphics card

There are a whole bunch of factors that determine how good a GPU is. Let's take a look at some of them:

  • GPU Bus Width: The width of the memory bus interface from the the GPU's memory to the it's processing units. Low end GPUs have low widths, thereby limiting the amount of data that can be transferred, causing a huge bottleneck
  • No of stream processors: Stream processors aka Shaders are dedicated units for performing pixel/vertex/geometric shading. Most recent GPUs don't have distinct types of shaders, the shaders are capable of performing pixel/vertex/geometric shading. Higher number of stream processor/shaders, faster the performance will be
  • Core clock / Memory clock / Shader Clock: The clock speed of each subsystem of a GPU. Of these, having a higher memory clock would mean faster transfer of data, thereby improving performance immensely. Memory clock is what I tend to improve upon when overclocking, it often results in huge boost.
  • Memory type: The type of the memory bus - Generally GDDR5 are known to provide the highest performance. GDDR3, DDR3 and DDR2 follow. There's a common misconception that the GPU memory type must match your main memory type; this is false and people trying to "match" the two memory types often end up with massive performance drops.
  • Drivers: Yes, yes, drivers are software, not hardware, but drivers make or break a GPU. I've seen driver updates which boost performance significantly. I'll refrain from mentioning which of the vendors have better drivers - that's another flame war waiting to happen.

You'll notice that I've not mentioned amount of memory anywhere above - that's because unless under extreme cases, the memory size simply doesn't matter. Unlike your RAM where more memory often results in faster performance - this isn't true because the memory in GPU is used as a frame buffer - for texture storage. As a result having 4GB on a low end GPU is worthless because the GPU cannot perform well enough to process those textures.

Other software/driver switches which cause performance drops/improvements:

  • Texture filtering: Texture filtering is the technique used to determine how good a texture looks. Most recent games would use Trilinear filtering - though Anisotropic filtering is also quite common. The number next to the filtering method : For example, 2x Anisotropic, 4x Anisotropic refers to the number of texture samples used for filtering. Higher number of samples, higher will be the texture quality. Consequently, increasing number of texture samples significantly increases the memory required to process the textures.
  • Anti Aliasing: Anti-aliasing is the technique used to smoothen the edges of polygons. There are different anti-aliasing techniques, some vendor specific some not so. Disabling AA is another way to improve performance.
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Have you tried the latest drivers for your card?

It's also worth checking on updated drivers for your motherboard.

The things that 'matter' with a graphics card are similar to the way your PC works:

GPU clockspeed - the actual processing power for all that rendering, the higher this clockspeed the more work it can do per cycle. Like a CPU.

Graphics memory - 1GB/2GB+ - the amount of RAM available to load all those textures into memory so they can be processed. Like your desktop RAM and opening large images/documents/videos.

Graphics memory speed/clockrate - the speed that things can be loaded into your GPU for processing, or loaded from disk into the GPU RAM area. The same as your desktop RAM speed.

Obviously the higher/larger the better for any of these, but all are very much relative to the costs of the graphics cards themselves. Some video editing based cards will have huge amounts of onboard memory, but not a high clockspeed, much the same way that the amount of RAM within physical Servers can be more important than Processor speed.

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Yes, I do - it's an ATI card so the drivers get released and updated quite often. –  tombull89 Aug 6 '12 at 14:28
    
As it's one of the mid-range cards, try the stuttering games with all AA and Texture Filtering off (the lower 2 parts of Sathya's answer) as these really impact the speed of lower cards. If you're still getting stuttering in something like BF:BC2 with all the lowest settings and AA off then you have a problem. It runs fine on my old ATI 9700 Pro (a card nearly 10 years old!) which probably means it's some kind of rendering fault with something on your card, probably not fixable (although this doesn't explain how 2142 is ok). –  HaydnWVN Aug 6 '12 at 16:20
    
@HaydnWVN probably the game engine is better tuned. –  Sathya Aug 7 '12 at 4:24
    
I still wouldn't expect to see a card 10 years old running a game made 4-5 years ago better than a card made around the same time? –  HaydnWVN Aug 7 '12 at 8:47
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