Discussion - Video RAM

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willirob

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Always wondered about video RAM (onboard GPU RAM)

Why do we need so much - is it all used, or does it actually make any difference above a certain threshold.

For example if you are running 1280*1024*32bit = 5242880 bytes

so you need only 5MB for the frame buffer

so assuming 256MB GPU RAM - whats the other 251MB used for
 
any games programmers out there shed any light on this - I understand that most games use triplpe buffers - so this would mean only 15MB for frames buffers
 
The framebuffer is only part of the video memory, the rest is mostly used for storing preloaded textures IIRC (rather than pulling them from disk or slow main memory). Also holds overlays and the GPU programs like shaders.
 
Ok - that makes sense thanks. I imagine with games these days, textures are pretty big and many. So Even a 512MB card would probably still use main memory to buffer textures
 
Before getting into any kind of depth ..and "depth", as in visual perception of 3D ..say in games and such, your initial premise is flawed in that you're forgetting refresh rate!

Your starting point should be 1280*1024 (resolution) *32bit (colour depth) *85Hz refresh rate (at least on a CRT, typically an LCD would be 60Hz) ..which brings us up to a somewhat higher memory requirement than you think! :cool: HowStuffWorks has an article here ..well, it's more of a fluff piece but there're more links at the end that, hopefully, lead you to more enlightenment (grasshopper) ;)
-bdt
 
Rkootknir said:
The framebuffer is only part of the video memory, the rest is mostly used for storing preloaded textures IIRC (rather than pulling them from disk or slow main memory). Also holds overlays and the GPU programs like shaders.
Click to expand...

Correct ... also all the vertex data (describes all the polygons making up your 3D models) is kept in there ... AGP and even PCIe bus is too slow compared to super fast and plenty GPU RAM is just easier to preload everything in there before a level starts than continuesly to load things into graphics memory from DVD or other memory like they do on games console.
 
willirob said:
Ok - that makes sense thanks. I imagine with games these days, textures are pretty big and many. So Even a 512MB card would probably still use main memory to buffer textures
Click to expand...

Most cards these days support texture compression.
 
thanks for the link

I don't agree that the refresh rate makes a difference, as only the current frame (an the next 2 in the case of triple buffering) are stored, but I am open to correction here. IF your refresh rate is 60Hz is doesn't store 60 frames in advance.
 
A screen's refresh rate capabilities has as much to do with a ("3D", hardware accelerated, textured and shaded) in-game fps rate as a bicycle has with a fish. What I was trying to point out is that the refresh rate requirement of a screen is an integral part of the memory requirement of a video card.
-bdt
 
Luke7777 said:
bdt, I can't believe you haven't linked to wikipedia even ONCE :D
Click to expand...
You, sir, are a bounder(wikipedia.org) and(dictionary.com) a cad(pantheon.org)! For some time now I've noticed you have FAR too much of a propensity to stick your oar in and stir things up, and mostly for that cause in and of itself and seldom as a device to move the discourse along. To you sir, I raise myself up and riposte with a "Bah*, humbug"(wikipedia.org)! :D (*url broken by the UTTERLY dumbass nanny software that runs this board, substitute the 1 for an i. :mad: )

hrm .. that's going to come across as really pretentious, isn't it? :rolleyes: But to now ignore the thrust and answer the body of your post: I did look at wikipedia's entry, as relates to this topic and decided against linking to it as it didn't do much to further the topic.
-bdt
 
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