Architecture compatibility question...

[Mike A Burns <mikeab soco agilent com>]

It appears 'arch_compat', or architecture compatibility is limited
to upward compatibility.  For instance, in working with a HP PA-RISC
machine running HP-UX 10.20, a package built on a 'hppa2.0' machine
will NOT install on a 'hppa1.1' machine, yet a hppa1.1 build will install
on a hphp2.0 machine.

An excerpt from my rpmrc file shows:
   arch_compat: hppa2.0: hppa1.2
   arch_compat: hppa1.2: hppa1.1
   arch_compat: hppa1.1: hppa1.0
   arch_compat: hppa1.0: parisc
   arch_compat: parisc: noarch

An excerpt from 'rpm --showrc' on a hppa2.0 machine:
   ARCHITECTURE AND OS:
   build arch            : hppa2.0
   compatible build archs: hppa2.0
   build os              : hpux10.20
   compatible build os's : hpux10.20
   install arch          : hppa2.0
   install os            : hpux10.20
   compatible archs      : hppa2.0 hppa1.1 hppa1.0 parisc noarch
   compatible os's       : hpux10.20 hpux10.10 hpux10.01 hpux10.00 hpux9.07 
			   hpux9.05 hpux9.04

An excerpt from 'rpm --showrc' on a hppa1.1 machine, using same rc file:
   ARCHITECTURE AND OS:
   build arch            : hppa1.1
   compatible build archs: hppa1.1
   build os              : hpux10.20
   compatible build os's : hpux10.20
   install arch          : hppa1.1
   install os            : hpux10.20
   compatible archs      : hppa1.1 hppa1.0 parisc noarch
   compatible os's       : hpux10.20 hpux10.10 hpux10.01 hpux10.00 hpux9.07 
			   hpux9.05 hpux9.04

*Notice the absence of 'hppa2.0' in the later, even though it uses the
 same rc file.

Now, my question is:  How can one build a package on a 'hppa2.0' machine
that will install on earlier, yet similar architectures (i.e. hppa1.1,
hppa1.0, etc.)?

Thanks,

Mike Burns
Agilent Technologies
Santa Rosa, CA