IBM Server CPU’s custom Intel CPU’s?

We have an IBM xSeries 342 Server that currently uses one Intel 1GHz CPU /133MHz with 256KB cache. We need to add a second CPU. Prices for an IBM CPU (which is speced out as above) is over $600. Of course, if we purchase an Intel CPU speced out as above – off the shelf – it is much cheaper. Does Intel really customize chips for IBM? Are we talking apples-apples or apples-oranges? I believe this is IBM’s way of raping the consumer..of course I have used Viking RAM in the server and it worksgreat..but IBM says Viking RAM is Ok to use. Any thoughts? I am guessing I would only invalidate the warranty, but not face any technological disaster? Right?