Minimal CP-M SBC design

[Allison]

>
>Subject: Re: Minimal CP-M SBC design
>   From: "Chuck Guzis" <cclist at sydex.com>
>   Date: Sun, 18 May 2008 10:31:45 -0700
>     To: cctalk at classiccmp.org
>
>> Date: Sun, 18 May 2008 10:09:45 +0100
>> From: Gordon JC Pearce 
>
>> Aha, I disagree.  You can't get at the innards of the 6120 at all,
>> because it's a chip.  If you want to get at the innards of an emulator
>> then you can, although how accurately the emulator models the logic of
>> the -8 might be an issue (my emulator doesn't model it at all, but
>> largely does its own thing).
>
>I was going to reply along the same lines, but I felt it might not 
>have convinced my audience.  Back in the old days of 22Nice, we added 
>an emulator feature that allowed a user to write his own port-mapping 
>code and include it with each program, allowing each individual 
>program to have its own simulated peripherals, if desired.
>
>This was no accident or a "feature for feature's sake".  A customer 
>was replacing a controller on a large piece of CNC machine tooling 
>(they made trailers for large trucks).  Communication with the 
>machine was largely RS-232, so that was no problem with the PC, but 
>the controller application directly manipulated a UARTs registers.  
>We rolled an emulator overlay for the UART that functionally mapped 
>the program's accesses to the PC's 8250-type UART.  It worked right 
>on the first try and the customer was happy for many years--and we 
>changed not a byte of code in the original program, nor our basic 
>product.
>
>That's the beauty of emulation--if the original box uses a bizarre 
>interface or unobtainium chip, you can emulate it.  MUCH easier than 
>trying to do the same in hardware.  Modern PCs tend to have 
>sufficient excess horsepower that you can emulate just about any 80's 
>era device without impacting performance.

That is the exact reverse case I was refering to. For that case and many
others like it I agree heartily.  One of the "sims" I use is VMware under 
Linux So I can run them crufy MS OSs without havignto invest hardware 
on a daily basis.  Doesn't hurt that I can also use it run a sim in 
a sim like MyZ80 inside W98se on the fast Linux machine.


>But, as I've said, I felt that I wasn't going to sway the hard-bitten 
>hardware folks.  As you pointed out, the line between hardware and 
>software is getting very blurry indeed.  Cheap, fast, 
>microcontrollers now give a new spin to tasks that would have 
>normally been accomplished with a pile of discrete logic and can now 
>be done with little more than software.

It works for me where it fits.  If I want Z80 hardware no amount fo sim
will make me happy but at the same time I may use a sim to build code 
for that Z80.  As I've done it that way and in reverse and also to solve 
the problem of hardware that is unobtaimium.

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.

Maybe time to chance the topic???   This is clearly outside the discussion
of how to make a minimalist CP/M system ( maybe even SBC).


Allison