Emulation vs. "the real thing" was: Re: Minimal CP-M SBC design

[Allison]

>
>Subject: Re: Emulation vs. "the real thing" was: Re: Minimal CP-M SBC design
>   From: "Chuck Guzis" <cclist at sydex.com>
>   Date: Mon, 19 May 2008 10:00:33 -0700
>     To: cctalk at classiccmp.org
>
>Allison wrote:
>
>> Where it works, I want to emulate a PDP1, or replace a PDP-11.  Where 
>> it doesn't work so well is when I want to run VMS on a MicroVAX with 
>> performance in the NVAX realm.
>
>As you stated, it depends upon what you want to do.  
>
>22Nice was written in response to those, who, back in 1986 still had 
>x80 CP/M systems and were looking to migrate to the PC.  It was the 
>answer to the question "...But how do I get my old <fill in the 
>application name> to work>?" The goal was not emulation of a Z80/8080 
>per se, but finding a way to make the transition to the MS-DOS world 
>as seamless as possible.  We didn't care about the 
>Osborne/Kaypro/whatever experience or the CP/M experience, only how 
>to get people going on a new platform.  By and large, it worked 
>pretty well, with no drivers, TSRs or knowledge about CP/M.  You 
>renamed your .COM files, ran GENCOM on them and you were off and 
>running.  The SUBMIT capability, for example, was deeemd superflous, 
>as the MS-DOS BAT capability was better in just about every way and 
>simple enough to adapt to. (The first versions of 22Nice ran on a 
>Compupro 85/88 S-100 machine, but that's another story).
>
>22Disk was written solely as a way to get files to 22Nice.  We'd 
>considered just making the package read-only, but "in for a penny, in 
>for a pound" thinking produced that bit of creeping featurism.
>
>To a CP/M purist, this approach (not providing an isolated emulated 
>Z80 that you could load CP/M into) was probably heresy, but it worked 
>well enough and accomplished the goal.  The rise of better PC 
>software eventually relegated 22Nice to the back burner, as that was 
>seen as the ultimate objective.

Well not a purist.  I've been using myz80 since around 94ish on PCs
for appliactions coding and other stuff.  Sicne then I've added 
Dave Dunfields Altair/Horizon  Em,ulator that has a few things I use.

Also 22nice as well.  However I didnt' ened it to port old z80 apps 
to the PC I found enough PC stuff to do the same or better that I 
didn't need that.

>I'd be lost without uC emulators today--they provide a convenient 
>quick code check without the labor of trying to figure out what the 
>heck is going on in that little block of plastic.  But my reason for 
>using an emulator there is very different from that of using 22Nice--
>I'm not interested in getting rid of the uC, but getting *to* it.

;)  Like Blackfin or PIC.

>I'll use an emulator to satisfy my curiosity for hard-to-get old 
>hardware.  I've used the SIMH 1620 emulator to scratch an itch in my 
>brain about some code I wrote 40+ years ago, but I would never 
>confuse that with the actual experience of using a 1620 with the 
>blinkenlights, parity checks, clackety console typewriter and 
>glacially slow execution.  Nor do I have the will or resources to 
>resurrect or construct my own CADET.  Nor do I want one in my office. 


;)  In somce ases MYz80 is far mroe capable or SIMH or any of the 
many others as I can besitting anywhere running the sim on a small 
laptop that I'd have any way rather than dragging my PX8 along as well.

>Sometimes, I'll use an emulator to figure out how some old piece of 
>software worked, such as WPS-I on an old DECStation.  The emulator in 
>this case is better than the real thing, because I can modify the 
>emulator code to show me what's happening internally.  This would be 
>at least very difficult on the real hardware--even if I really had it 
>at hand.  

Yes, it's a debugger and tool.  


>This gets back to why I questioned the lack of diskette drives on a 
>"real" Z80 design running CP/M.  It seemed to me that if one is after 
>an "experience" and is willing to go to considerable lengths to get 
>it, that it should be as accurate and complete as possible.  While 3D 
>computer simulation of skydiving can be made to be very accurate, 
>there's nothing like jumping out of a real aircraft for realism.  
>Having noiseless, crashproof RAM-drives just wouldn't do it for me.

;)  Having had noisy crash prone drives ( and still having many) 
if I want to build to explore some part/hack of CP/M it's usually 
not writing yafd (yet another floppy driver).  CF allows me to 
build and pay attention to other things that might be more hardware
and software intensive.  Examples over the years is low DC power 
systems, page mappers and the memory management software.  Both 
hard to do in a sim but the sim can help in creating the code.


>It all depends upon what your objective is.

It always do. ;)

Allison


>Cheers,
>Chuck