turbocache, shared and dedicated memory

hi there, just wondering mainly what the difference is between the three types of memory. i get dedicated, thats easy, memory specifically used for games. but, i'm concerned about how much the graphics suffer from using turbocache (or shared) memory as opposed to using dedicated. and i don't actually know if turbocache and shared are the same thing.

i'm looking for a laptop right now and all i'm getting is 1023mb shared with 256mb dedicated. does this mean that if the game needs more memory it'll use 1023mb of system RAM then give it back when its finished with it? and will this deteriorate normal system performance because its also used for games? because i've heard that according to the system it will sometimes only recognize , for instance, if you had a system with 1024mb of RAM, and 256mb of memory shared (or turbocache), it appears as having 768mb of RAM because the shared memory is used for games and not sysem processes. or is that specific to shared memory only systems?

i know its alot of questions but i'm dying to work all this terminology out, so any input would be greatly appreciated, thank you!

Jam it back in, in the dark.

most of what you're wondering about i cannot answer. However, i can share my info cuz i wanted to buy a 7300LE way back (which uses Turbocache) and i advise avoiding it, since you're more likely to get bottlenecked since vram onboard the gfx card eliminates the need to go through the motherboard to the main ram. in other words a "256- up to 512" card is not much better than a regular 256 since its mainly the chipset and not the vram that determines performance (assuming you don't game 4000x2000 or something ( i never get today's resolutions))

I know this sounds cliche but shared and trubocache cards have too many ways in which their performance can be hindered, avoid them anyway.

There's nowhere I can't reach.

but the thing is most of the cards integrated into laptops do have shared memory, i don't think i've been able to find a solely dedicated graphics card, there's always shared memory with it.

edit: slightly off subject, but does anybody of any laptop customize sites apart from alienware? they're kind of expensive.

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Shared memory and Turbocache are just buzzwords. These technologies are not new. They're quite indeed quite old.

As you stated dedicated memory is physical memory owning only by the GPU. Only the GPU uses it and you only have access to it through the GPU (this is not entirely correct, but otherwise you would have to go into great detail).

I think everyone still knows AGP. The AG port already allowed shared memory when it was first introduced. Thats the AGP aperture size. It's first used when the GPU runs out of his own physical memory. It then transfers data to the main memory, making space for new stuff. Graphics APIs like OpenGL also allow it to upload data to the AGP, so you have a choice which memory you want to use.

I am a dolphin, do you want me on your body?

just out of curiosity, what would be better? a solely dedicated card or a dedicated card with shared memory?

I was speaking idiomatically.

There is no card with solely dedicated memory. GPUs can always access main memory to swap data out (*). What you want is a card with a sane amount of physical (dedicated) memory.

(*)It can of course be disabled, like AGP could be completly disabled in the BIOS:

What kind of toxic man-thing is happening now?

ah, thats interesting, if you go to customize a laptop on alienware, they only specify the dedicated allocation. does that mean that it has shared memory and they're just not telling you?

FELIPE NO

Highly possible. Disallowing the GPU the access to main memory would hurt performance so I doubt they disable any of these features.

Always keep in mind that this shared memory / turbocache thing is only there to convince you to buy the product. Shared memory was always there but the vendors have realized that it makes a difference when they explicetly state that the product can use shared memory. Makes the customer believe he gets more for his money, although that's simply not the case.

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so basically look for the dedicated memory allocation and the more shared memory the better?

Jam it back in, in the dark.

Try to get as much physical (dedicated) memory as possible (as much as your budget allows). The shared memory amount isn't really important.

Short explanation:
You get good performance with your GPU when everything (geometry data and textures) fits into the dedicated memory on the card. As soon as there is no more space left on the card the driver/application is going to use the main memory. Now I should note that the card can't use ALL of the main memory, but only a fraction of it. But that doesn't really matter, because:
- As soon as data is 'swapped' out of the dedicated graphics memory the performance is going to collapse. I'm assuming the application that renders needs every bit of data it stores in the memory (both main and dedicated) to construct a frame. Which means it has to transfer data back and forth from and to the main memory to render the scene. Main memory is quite slow compared to the dedicated GPU memory. Now you're limited by your main memory speed and by the bus speed the data is transferred through. That results in a huge performance degradation.
- As soon as you notice that the FPS collapses you're going to reduce game settings, like geometry detail, texture resolution, decal amount, etc. - because you don't want crappy performance that makes it impossible to play.
- After adjusting settings everything fits into GPU memory again, so you can play with good performance

The whole thing is of course simplified. There a cases where using the main memory instead of the GPU memory is wise, but that's another story,

There's nowhere I can't reach.

thanks very much, thats cleared everything up, liquidacid. so they only tell you the shared memory amount because they have to, but the fact is that is really pointless to have if you want to run a game smothly without any frame degradation, hey, its not that hard to understand. thanks liquidacid and everybody else who posted.

This thing is sticky, and I don't like it. I don't appreciate it.