[Coco] FPGA 6809

[Tormod Volden]

On Mon, Aug 31, 2015 at 8:27 AM, Bill Nobel  wrote:
> Oh it is definietly possible, but the thing is DOS from Disk Extended basic only does track 34.  On the other hand, you can do a pre-boot, that will accommodate a much larger boot sector by loading boot A (regular dos command), then load B which is called from A.
>
>> On Aug 31, 2015, at 12:14 AM, Dave Philipsen wrote:
>>
>> I see that the Boot, REL, and Krn modules reside on the boot track and they are limited in size to $1200 bytes.  I have surmised that this limitation is due to the fact that the originally floppy storage medium had $1200 bytes in a track and it was convenient to load in one track (track 34) and then relocate that data to a more convenient place in memory.  There, the Boot module has just enough smarts to initialize the storage device and read raw sectors.  The Krn module has just enough of the OS9 system to get the rest of the operating system loaded in from the OS9Boot file.  Well, the code I have for initializing the SD card and for reading sectors so far is just a little too large to fit into the space of the existing Boot module.  Additionally, it seems there are some 'hard-coded' portions of these three modules and that is why there is some padding in the source code so that the modules always retain a certain size.  So my question is; wouldn't it be possible to adjust these three modules to allow for a slightly larger boot track?  I'm thinking that instead of loading the boot track from $D00 - 1F00 perhaps we could add two more sectors and copy the boot track with a size of $1400 to the area of $B00 - 1F00 (of memory block 3F).  This obviously wouldn't work on a real stock CoCo 3 since the DOS command is hard coded to load just 18 sectors but I'm loooking more at a customized version.  There is another way to do this too and that would be to do a two-step load of the boot track but I'm not really keen on that idea.
>>

For alternatives to the boot track bootstrap in NitrOS-9, please take
a look at Brett's ccbkrn concept. He lets something else (his CoCoBoot
program) load the modules into memory before handing execution to a
modified NitrOS-9 kernel. CoCoBoot is written for DECB I believe, but
it should be portable to a barebone system, and is written in Forth. I
am sure Brett will correct me if I got something wrong :)

Regards,
Tormod