[geeks] 400 in AS/400

[geeks at sunhelp.org]

 Figuring somebody here would know the answer:

  What does the 400 in AS/400 stand for?!? I've got a nice book here, but they 
only mention Application Server and I would guess the 4 comes after the 3 from 
s/3x. Or is it as simple as implementation 00 of system 4?

 And the bonus question:

  What does the 6000 in rs/6000 stand for? I've also never come accross an 
explanation of this one.

  thanks,
    Michiel