Memory Size Requirement to Run Linux on Embedded Environment

[David, Albert]

Hi everyone!
I am new to linux and my current project is to port linux on our custom
hardware based on PPC405EP(AMCC).
Currently we are in a hardware design phase but I am finding it hard to
decide the Flash and SDRAM Memory size.
We are planning to us 2.6 Kernel, with minimum hardware interfaces.

Should we use Kernel 2.4 or 2.6?

Main components of my target device are as follows..

1)AMCC PPC405EP processor operating at 66.66Mhz External Oscillator(Hope we
can go for higher operating frequencies by configuring internal registers of
PPC).
2)Virtex-2 Pro FPGA - memory mapped to PPC405.
3)Ethernet Connectivity.
4)IrDA.
5)Two RS232 Serial Ports.
6) IIC Bus.


I assume the binary size of my application that will run on linux would be
around 2 to 3 MB. By considering these facts of my hardware, what would be
the size of kernel? And how many drivers I may require? What would be the
size of my root file system? 

Is it necessary to have a NAND Flash to handle the power failures? Or any
CFI compliant NOR Flash would do!

There will be parameters of about 65KB are to be used and these parameters
can be changed in the field. This parameter block will have 2 copies to
avoid data corruption due to power fail. Hence to avoid the use of NAND
Flash I will be using 2 Parameter files to read and write(into flash) in a
linux environment during normal operation. Am I right??

In this mailing list I have read the typical size of U-BOOT will be around
256KB as suggested by Wolfgang Denk.

A rough approximation of Flash and SDRAM size would help me a lot to proceed
with my hardware design. 

Pardon me If I am asking too basic questions, I know I have to do lot of
reading before I proceed. 
Your inputs are valuable to me!

Thanks in advance for your support,
BR,
Albert David.

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