difference between IBM mainframe and AS400?

[Mainframe help]

I have been working on IBM Mainframe for some time and I had been programmer for it. I have been asked to look in one of the projects we have which works on AS400. I have no idea about AS400. Can anyone please tell me what is the difference between IBM mainframe and AS400?

[Robert Sample]

This is one of those questions that are EASILY answered by Google; check out a number of the IBM web pages on the AS400 for details.  The AS400 has a different architecture, different operating system, different file system -- basically mostly what is the same is the IBM name.

[Mainframe help]

Thanks. I did search but I was asking from architecture point of view...

[Robert Sample]

Google is your friend.  Googling as 400 architecture returned over 18 million hits and several on the first page give details about the AS 400 and its successors.  Googling z/architecture returned over 4 million hits and again several on the first page give details about the architecture.  You need to replicate these results and start reading.  Asking a question about differences between architectures is like asking "How high is up?" - the answer largely depends upon how many details you want to get into.