To be asking such a question, Alexander, is only suggestive of one thing......that the Graphics 'set-up', whether it be 'on-board'' or 'add-on'....of your computer is totally inadequate, to start with.
It (your enquiry) is also suggestive....that you do not want to go and buy another Graphics-card capable of providing the required RAM you personally wnat for your computer.
Please, take note, that with most of the newer types of Motherboards, these days, do come 'fully equipped'....with ample Graphics RAM. (The 'standard' is roughly 256Mbs.......for on-board Graphics.)
Mine (a ASUS M2A-VM motherboard) has such an amount.
When I addded an 'add-in' Graphics-card, this amount got boosted (yeah, that's right...boosted) to 512 Mbs.....utilizing the
on-board Graphics RAM, to boost my Graphics capacity.
With this paricular Graphics-card (an ATI/AMD one), if I was to use a 64-bit OS....which is what I , at the moment, am experimenting with...........this amount does INCREASE (dramatically, to what you may ask ?)....
1 Gb.....of Graphics RAM.
In short, like many others who have bought themselves an adequately-sized Graphics-card...to start with, I do not have to 'fiddle with it'....to produce more RAM capabilties, for a Graphics-card that simply isn't able to perform properly...under normal circumstances.
'If' chosen, I could also 'include'.....the on-board Graphics RAM, to this TOTAL.(How ?......by simply 'activating' the Onboard Graphics, then, switching to the 'add-in version'.)
This, alone, would have given me 768 Mbs of RAM (on a 32-bit OS)!
Not true, you say!
Hmmmm, something is drastically wrong with your 'theory', then,
.......because I have already done it.
The 'secret'....of my success, is just that the Brand of Graphics (of my computer)...on-board/add-in....are ASUS (ATI/AMD).
Yes, the same Principle (of using 'matched' RAM modules) does apply here, too.
The 'matching' is in the Brand Name, not the capacity, as ASUS would undoubtably use very similar RAM chips...in ALL their applications.
So, Alexander, it's your choice....to continue on fiddling, or, to go buy an adequate Graphics-card (that will deliver that 'boost',in RAM, you're after).