Andreas Brusinsky wrote:
> 
> So there is really a serial line with 460800 Baud (i.e. port 1)?

That's the 'dca' port, yes.

> But this could be only used to connect two hp425?
> Or would there be another application for it?

You could try changing the crystal on the HP's motherboard
(I think the dca is clocked off the 7.~ MHz ISA clock crystal)
to some multiple of the 1.8MHz clock used by PC serial 
interfaces; it shouldn't be too hard to find something suitable.

--
Mike Smith  *BSD hack  Unix hardware collector
The question "why are the fundamental laws of nature mathematical"
invites the trivial response "because we define as fundamental those
laws which are mathematical".  Paul Davies, _The_Mind_of_God_