From: uhclemLOSE.sep07@nemesis.lonestar.org   
      
   zwsdotcom@gmail.com wrote:   
   : I've just acquired a large collection of Model II stuff, and I'm going   
   : through it, cleaning and testing. I'm puzzled though - why is there no   
   : Model II emulator in the world? Many far more obscure systems have   
   : emulators.   
      
   With regard to the question of "Why no Emulator?"   I would suggest   
   these points contribute to the lack of interest to make an emulator   
   for these systems:   
      
   SOFTWARE   
      
   1.	TRSDOS 2.0 and TRSDOS-II were slow and stable but not   
   	remarkable, nor were the applications, most of which were   
   	targeted at business users.   
      
   2.	TRSDOS-16 aka "Bowling Ball DOS" was a disaster.  No attempt   
   	should be made to bring it back in any form.   
      
   3.	Some versions of CP/M and LS-DOS were also reasonably nice   
   	operating systems on these systems, but as with TRSDOS, few apps   
   	were meant for consumers.  Is there anybody out there today   
   	who wants to run a accounts payable package written in COBOL   
   	with absolutely no "clicky-pointy"?   
      
   4.	XENIX - particularly version 3.2 and later -  was good   
   	but was also for business or very advanced programming types.   
   	In this day you can get a far better UNIX environment   
   	with full networking support and paged memory management   
   	on any PC running at 20MHz or faster.   
      
      
   SOFTWARE & HARDWARE TECHNICAL DETAILS   
      
   5.	Tandy was somewhat reluctant to publish many technical details   
   	of the Model II/12/16/16B/6000 hardware, and highly resistant   
   	to releasing details about the TRSDOS/TRSDOS-II operating   
   	systems.  There were a number of reasons for this and few   
   	made sense even back then, but the result was a chilling   
   	effect and the number of third party add-on hardware devices   
   	and software applications not specifically contracted by Tandy   
   	was low compared to what existed on the Model I/III/4/4D/4P family.   
      
      
   HARDWARE   
      
   6.	There are lots of emulators of the Z-80 processor running in   
   	IM 0 or IM 1 mode out there, but there probably aren't a lot of   
   	emulators that bothered to implement IM 2 mode.  This is   
   	required to emulate almost any Model II/12/16/16B/6000   
   	environment.  The Model I/III/4/4D/4P did not use IM 2 mode.   
      
   7.	The Model II/12/16/16B/6000 used the Zilog DMA, CTC and   
   	SIO chips.  For their day these were sophisticated devices   
   	that required careful programming, and an accurate emulation of   
   	their behavior isn't trivial, particularly their interactions with   
   	IM 2 mode interrupts.  The Model I/III/4/4D/4P did not use   
   	any of these devices.  Emulation of the Zilog DMA chip is   
   	generally required to boot from floppy on this system.   
      
   8.	Apart from the rarely seen ARCNET card, only RS-232 serial   
   	is available for communication.  Each require even more   
   	hardware to be emulated.   
      
   9.	The Model 16/16B/6000 680xx processor set is also unique.   
   	While emulations of the 680xx processor itself are common   
   	(most DVD players contain one so as to run the CD-I-like   
   	menu system), the way non-typical peripherals chips are attached   
   	and how the 68000 environment is also visible and alterable by   
   	the Z-80 adds even more complexity to an emulation.   
      
      
   There are probably additional reasons, but combined those certainly   
   create a lack of interest in emulating the platform today.   
      
      
      
   Frank Durda IV - send mail to this address and remove the "LOSE":   
       http://nemesis.lonestar.org   
      "The Knights who say "LETNi" demand... A SEGMENT REGISTER!!!"   
      "A what?"  "LETNi! LETNi! LETNi!" - 1983   
   Copyright 2007, ask before reprinting.   
      
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