[Coco] NitrOS9 question

[Dave Philipsen]

So this is my plan.  I have a working OS9Boot file I use for CoCo3FPGA.  
It does not require the REL or Boot modules since it uses Brett Gordon's 
bootloader.  I have enhanced Brett's bootloader by adding the capability 
to load an alternate OS9Boot file by holding down the ALT key when 
booting (loads file named OS9Boot.1). This way, I can experiment on the 
CoCo3FPGA with the alternate bootfile by removing unnecessary modules 
and getting the system to boot with a shell on one of the serial ports.  
My goal is to get it to boot _without_ CoWin, KeyDrv, JoyDrv, SndDrv, 
RAMD, R0, and the window descriptors.  I've already got it booting 
without SndDrv, RBDW, DWIO, and the window descriptors.  I'm not yet 
sure if VTIO needs to be left in place or not.

Once I get the CoCo3FPGA booting a slim version of OS9 Level 2 then I 
will get the sources for all of the modules used and start searching for 
CoCo-specific references.  These will be removed or replaced with the 
correct code for my generic system.  I believe that essentially all that 
is needed is a CoCo 3 compatible MMU and some sort of timer/interrupt to 
generate the system ticks.  Mostly, I just need to get rid of any video 
specific stuff.  With my target system I have a system monitor which 
allows me to upload a Motorola S-Record file and burn it to flash.  From 
CoCo3FPGA I will create a batch file that will assemble all of the 
necessary modules and merge them together into a single file which will 
be converted into an S-record file.  I'll write a utility into the 
system monitor which copies the code from flash to RAM at the 
appropriate addresses and jumps to the boot entry point.

I can follow the boot sequence and insert some debug code at different 
strategic locations to check for problems along the way. Once I get the 
slim code up and running on the target system then I'll experiment with 
a new video system that will run 1024x600 video at a 50 MHz dot clock.  
The system will ultimately have just a single gfx-mode window (Term) as 
I do not need the window switching capability for my specific 
application.  I think I've sketched out the timing on that so it will 
work effectively sharing system/video RAM with the 25 MHz CPU getting 
access to it on the low side of the E clock and the video system getting 
access during the hi side of the E clock.

Dave


On 9/29/2017 9:37 AM, Neal Crook wrote:
> Well, there are only 2 L2 platforms in the repository. Start with the CoCo
> one if you think it will be easier... but don't come crying later!
>
> On 29 Sep 2017 14:01, "Dave Philipsen" <dave at davebiz.com> wrote:
>
>> I was afraid you were gonna say that! 😛
>>
>> Dave
>>
>>> On Sep 29, 2017, at 3:03 AM, Neal Crook <foofoobedoo at gmail.com> wrote:
>>>
>>> Dave,
>>>
>>> I recommend that you use my multicomp port as your starting - point.  I
>>> also recommend that you do a L1 port first because it will provide an
>>> easier debug path for and drivers you need. All the code is in the
>> official
>>> repository.
>>>
>>> Neal.
>>>
>>>> On 29 Sep 2017 05:48, "Dave Philipsen" <dave at davebiz.com> wrote:
>>>>
>>>> I have a question about NitrOS9 that I hope someone can help me with. I
>>>> would like to attempt to port a version of Level 2 over to a new
>> non-CoCo
>>>> platform.  Essentially, I should be able to replicate the functionality
>> of
>>>> the CoCo MMU but I don’t want or need all of the gfx stuff that the
>> CoCo 3
>>>> has.  I would like to initially have it boot up with a shell on a serial
>>>> port but I definitely want to have access to the full 512k via the
>> MMU.  So
>>>> that means I don’t need any of the CoCo keyboard stuff either.  Just
>>>> accessing it via serial port(s).  What image is going to be the best to
>>>> start with? Also, what are the ‘headless’ images?
>>>>
>>>>
>>>> Dave
>>>>
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