[U-Boot-Users] u-boot config

[Alfred]

Hi,

I am absolutely new to u-boot and am trying to understand.

We have a IXDP425 based system, if I undnerstand it correctly.
One needs to hard code the system ram value at compile time itself.

Can some one tell me why dynamic probe of memory like in PC not possible ?  
are there any registers one can read to find this out ?? 
we would like to have dynamically probed memory configured by u-boot.

Also, Can some one please explain / point to me some page / doc which describes 
what makes up the u-boot config area ?

Cheers,
Alfred