Shared RAM

[David Niemi]

 Mon, 2005-21-02 at 04:17 -0300, Pedro Fernandes Macedo wrote:
> Mark Panen wrote:
> 
> >Hi
> >
> >How does this shared RAM story work. My laptop specs state that i have
> >512 MB RAM but free only shows about 448, ok so i know 64 is going to
> >the vga card.
> >
> >What my question is, have i got 512 installed or do i have 448
> >installed and a 64 MB vga card, maybe i should answer my own quesion
> >as i don't think you get 448 MB RAM.
> >
> >I just don't understand why free shows up 448  and not 512 ? Is the
> >vga chip taking the RAM away on boot ?
> >  
> >
> You have a total of 512MB of RAM. To save money easily , the 
> manufacturer of your laptop decided
> that he wouldnt put dedicated memory for the VGA, so he set it up to use 
> part of the main system memory as
> the VGA memory. Call them cheap bastards if you want ;)
> After booting , the BIOS reserves the ammount of memory according to the 
> value set on BIOS and reports the RAM
> to be 512MB minus the part reserved for the VGA card , hence the value 
> of 448MB shown on free...
> 
> If you want , usually you can change this config on the BIOS from 32 MB 
> up to 128MB (I think.. It's been awhile
> since I last used a computer with onboard video)
> 
> --
> Pedro Macedo

Just to intrude another question along similar lines: what about for
those systems with an AGP or PCI(-X) card that have their own RAM and
there is also a similar amount of system RAM alocated to AGP/PCI
graphics called "AGP Aperature Size" or similar in the motherboard's
BIOS.

Why is there a similar amount of system RAM allocated?  

Dave