Date   : Mon, 08 Aug 1994 09:56:11 EST
From   : Stephen Quan <quan@...>
Subject: more on emulator implementation.

This is extracted from 1-1 email between me a Chris Rae:

Chris Rae writes :

> Re LODSB vs LAHF - don't worry about questioning my logic! The only way 
> programs progress is by having their logic questioned. I never really 
> meant that my way was the "correct" way and yours wasn't; we've really 
> just chosen different ways of going about things. BTW, how *do* you 
> handle the flags?

Ok, what I have done (at it is in operation now).  Is design not 1 emulator
but 16 emulators.  In other words, I have 16 256-branching loops and so
forth.  Each emulator for every combination of N,V,Z and C.  I have called
my emulators N0V0Z0C0 .... N1V1Z1C1.  For instance, say if I had to
implement SEC for one of my emulators, e.g.

   N0V0Z0C0_SEC:
     jmp N0V0Z0C1

For more complex instructions :

   N0V0Z0C0_INX:
     inc cl              (or whatever register that holds X)
     js  N1V0Z0C0
     jnz N0V0Z0C0
     jmp N0V0Z1C0

So you see, I am really using the PC's status registers after all.
-- 
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).