SRAM vs SDRAM

Hi,

I am about to design a system with uClinux, and I was wondering if the performances would be correct if I only used an SDRAM. SRAM is a bit expensive if I want to have enough memory to run my linux (I guess I need at least 4MB). However, I have read in some threads around here that SDRAM performances were quite bad. Is there any experience here of people running linux without SRAM ?

My second question is quite the same and about the Altera Cyclone devboard : I use the standard design (using SRAM as exception address thus), and I follow the Quick Start Guide to build a kernel, that I run from the SDRAM. In this case, I suppose the whole kernel is uploaded in SDRAM and then executed from there. My question is : is the SRAM still in use ? Do I lose any performance if I remove it ? I can see that ramfs file systems are mounted but I guess its only in SDRAM. I suppose the /dev/ramX are linked to the SDRAM, not the SRAM, so is the SRAM in use ?

Thanks a lot

cetic