Advantages of Dedicated vs Shared Ram

Iam wondering what the distinct advantages are of having dedicated memory on your graphics card or having shared ram when comparing a low end dedicated system to a higher end shared graphics card(if any). So if I had 2 computers identical only one with on board graphics with shared ram and one with dedicated ram(lower end graphics card), now the one with shared would have more ram then ever needed so say if the most the computer ever would use would be 2gb, and it had 4gb(ddr3 1066 in the case if it matters) and had the capability to share 256MB there would never be an issue of running out of ram or even coming close. And the dedicated had 256MB of memory would there be any advantage of having the dedicated card over the shared if the cards themselvs were similar in specs.

 

Ded RAM for GPU is positioned more closely to the GPU and I it's just for GPU, and might be faster or w.e. In any case, ded RAM gets you better performance than just pure shared RAM.

In most cases, GPUs will not need to use the shared portion of the RAM if they have ded RAM. 256 MB ded you MIGHT need to use the shared, but it won't use 2 GB of shared. I'd say that the lower end GPU with ded RAM will outperform the other one, but if the GPU difference is a lot then maybe no. I think the crappiest ded GPU can beat the best integrated GPU (probably wrong, but I skimmed that GPU rankings page and it seemed so).

 

Dedicated video memory is optimized for video use i.e. it's of GDDR interface normally

Regular system RAM is of DDR standard(GDDR is based on DDR, but is optimized for graphics rendering).

So that would be the main difference between shared and dedicated memory.

If everything else is the same(shader count, clocks etc.) then the dedicated memory would perform better. IGPs aren't gimped because of lack of dedicated memory, they're just gimped period. I could stick 1Gb of GDDR3 on a GMA4500 and it'd still suck.

 

Even worse, to access Shared Memory, the GPU has to go through the CPU......

 

even on dedicated cards ram isn't all. for example a 8600 GT with 256mb would have a similar performance (less then 5% difference if much and only at very high resolutions) to a 8600 GT with 1gb.
it isn't all about the amount of memory. it's much more about the gpu itself.