High use of video memory shared when starting a game using Nvidia GPU

Thread not is about bugs, but just share a strange detail.
When starting a game in loading precompiled shaders is used more of 800 MB of video memory shared in system RAM instead of using GPU memory.
When the game is totally loaded GPU memory used is less of 300 MB and 800 MB to 1 GB system memory is used.
Using Nvidia GeForce GT 640 driver version 388.71.
Anyone user here in forum using Radeon GPU having the same issue ?
Thanks for read my thread.

NVIDIA drivers cause high RAM usage as more and more shaders are loaded. Not an issue on AMD.

I had a Radeon HD 3300 and 3450. Both had problems in driver compatibility.
Nvidia has much less problems and more support for new driver features.
Have times that the use more of 1 GB just loading shaders.
Perhaps Nvidia will optimize future drivers avoiding that problem ?
Have a nice day.

NVIDIA has support for new features which AMD doesn't have like? They both support the same APIs.
You can't pick an ancient card and complain it doesn't have support for recent APIs and drivers, of course it doesn't.
I've been told NVIDIA spawns extra branched shaders as optimizations, which we don't really need here, but it really increases RAM usage when compared to AMD drivers.
They already lowered RAM usage, although it's still high. I'm not sure if they can or are willing to push improvements to lower RAM usage even more.
Basically, if you're low on RAM, AMD drivers are the way to go, either that or you'll have to get more RAM.