Date : Mon, 18 Jul 1994 10:10:19 EST
From : Stephen Quan <quan@...>
Subject: Another little progress update... (fwd)
> Using the Z and C flags shared between two processors is working
> incredibly. I have managed to get through a fair number of instructions
> as a result of them now being so easy to write. However, I am having a
> couple of problems - the major one being how the hell I am supposed to
> get 65536 bytes of memory (a whole segment) to myself on a PC. Does
> anyone have a sure-fire way of getting 65536 bytes of contiguous memory
> on a PC? I'm posting to newsgroups about this too so don't worry if you
> don't!
EMS page frame! It will handle the job perfectly!!!
Get it to allocate you four pages of 16K EMS memory and map them into
E0000, E4000, E8000,m EC000. Basically there are only a few calls to
do this, if interested I will dig up all the material I have on EMS memory.
This is what I was talking about early about being able to map in different
EMS page frames into E8000 and EC000. So ignoring the E in front, you have
the perfect representation of beeb memory. As well as the mapping allows
you to simulate switching in of sideways ROM. All of these features are
only 1 DOS interrupt away! :-) :-)
But you must have loaded in your CONFIG.SYS
HIMEM.SYS
EMM386.EXE
Just the typical configuration for all currently PCs today.
Since in your other posts implies that you are programming your emulator
in PC assembly, I definitely recommend you search for the files
HELPPC21.ZIP
INTER41A.ZIP
INTER41B.ZIP
INTER41C.ZIP
INTER41D.ZIP
They give invaluable information on PC DOS and BIOS interrupts which
covers EMS memory and a whole host of other PC hardware interfacing
via assembly. Invaluable source of material, I'd say!
--
Stephen Quan (quan@... ), SysAdmin, Analyst/Programmer.
Centre for Spatial Information Studies, University of Tasmania, Hobart.
GPO BOX 252C, Australia, 7001. Local Tel: (002) 202898 Fax: (002) 240282
International Callers use +6102 instead of (002).