Date   : Fri, 15 May 1987 09:59:21-PDT
From   : D-ROGERS@EDWARDS-2060.ARPA
Subject: HD64180 PAGING

>14-May-87 21:24:45-PDT,870;000000000001
>From:     <V125KJG8%UBVMS.BITNET@wiscvm.wisc.edu>
>Subject:  Bank Switching Z-System on the HD64180
>
>Can anybody out there figure out a way to effectively bank switch the BDOS
>and BIOS portion of Z-System into bank 1 (or any other bank) of the HD64180
>so I can push the TPA size over my cramped 49K?  Any hints or helps out there
>would be appreciated.
>
>  --Curtis R. Anderson
>  State University of New York at Buffalo

       I suspect you will have to work out a jump_over arrangement, the
way PDP11 macro programmers have to avoid the I/O page.  I don't have an
HD64180 but the data sheets i received from Hitachi seem to indicate that
the paging is accomplished similarly to the PDP's Page Descriptor Reg's.
       A possible alternative would be to put the BDOS & BIOS in the last
page and write the page switching into the jump chain - more difficult to
impliment, but maybe easier to use over the long run.          [dale]