vram memory upgrade

[rookieme]

I was thinking if it's possible to upgrade some motherboard's vram.
So I have some of old dv6000 and dv9000s.
Dv6000s have vram ranging from 128 to 256MB with chip G86-730-A2.
Dv9000s have vram from 128 to 512 MB [G86-730-A2 with the 128MB and G86-770-A2 with 512MB]
According to schematics dv6000s had 64bit gpu and dv9000s 128bit.
Also noticed that dv6000s only use only 4 of 8 slots for vram and dv9000 all the 8 slots so for a start I can try to replace G86-730-A2 with G86-770-A2 at dv6000 and simply add 4 rams at vram slots so I could double the memory size of gpu?
I have the part number of the vrams
HY5PS561621AFP-25 [256Mb(16Mx16) DDR2 SDRAM] x8 = 256MB
HY5PS121621CFP-25 [512Mb(32Mx16) DDR2 SDRAM] x8 = 512MB
That way i could create a dv6000 with 512MB vram that only the dv9000 had.
I prefer a dv6000 for everyday usage...
Now I'm wondering if it could be possible to find compatible rams chips with specs 1024MB(64Mx16) DDR2 SDRAM and could this work for me so I could end with 1GB vram or the gpu G86-770-A2 doesn't support that much?

[rookieme]

Re: vram memory upgrade

http://www.nvidia.com/object/geforce_8600M.html
According that link its max vram is 512MB.
Now I'm wondering if I can use 8600 GT chipset instead of 8600 GS.
8600 GT was used by apple at macbook pro 2008 models - yes they had the same issues that dv9000s had with GPUs.