we have DELL 6800 server (Xeon 64 bits) with Redhat As
4.0 (64 bits) installed on it.

After I installed ORACLE LINUX 10GR2 64 bits software
and I found following:

    select platform_id, platform_name from v$database;

     13
     Linux 64-bit for AMD

is it typo for ORACLE? does it mean INTEL chip not
compatible with 64 bit ORACLE?

Thanks.

AMD came out with the x86-64 instruction set long before Intel did - way back when the Itanium chip was where Intel wanted the market to go ... along with HP.
Intel later grudgingly adopted the features, branded as "EM64T".

hth.

Paul